#antennas — Public Fediverse posts

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

📡 Ah, yes, the granddaddy of all #antennas that no one asked for! Finn spent a decade constructing this colossal contraption in his backyard—because nothing screams midlife crisis like a 32x17 #Yagi monstrosity. 🤦‍♂️ Now he can talk to the moon while the rest of us are stuck debating if we should upgrade our Wi-Fi routers. 🌙📶
https://la0by.darc.de/LA8YB_EME_MBA.htm #midlifecrisis #backyardprojects #hamradio #antenna #HackerNews #ngated

Entropy’s Rotoscope Issue I [page 5/19]

https://kamiokan.de/entropysrotoscope/issue1

RSS: https://kamiokan.de/entropysrotoscope/rss.xml

Support me on ko-fi: https://ko-fi.com/j_g00da

CC0 / Public Domain

Next page tomorrow.

#unix_surrealism #comic #art #entropysrotoscope #kamiokande #snails #antennas

Entropy’s Rotoscope Issue I [page 5/19]

https://kamiokan.de/entropysrotoscope/issue1

RSS: https://kamiokan.de/entropysrotoscope/rss.xml

Support me on ko-fi: https://ko-fi.com/j_g00da

CC0 / Public Domain

Next page tomorrow.

#unix_surrealism #comic #art #entropysrotoscope #kamiokande #snails #antennas

Entropy’s Rotoscope Issue I [page 5/19]

https://kamiokan.de/entropysrotoscope/issue1

RSS: https://kamiokan.de/entropysrotoscope/rss.xml

Support me on ko-fi: https://ko-fi.com/j_g00da

CC0 / Public Domain

Next page tomorrow.

#unix_surrealism #comic #art #entropysrotoscope #kamiokande #snails #antennas

Entropy’s Rotoscope Issue I [page 5/19]

https://kamiokan.de/entropysrotoscope/issue1

RSS: https://kamiokan.de/entropysrotoscope/rss.xml

Support me on ko-fi: https://ko-fi.com/j_g00da

CC0 / Public Domain

Next page tomorrow.

#unix_surrealism #comic #art #entropysrotoscope #kamiokande #snails #antennas

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A short 2-band ladder line antenna for portable ops

Introducing the 2B2L antenna

Wouldn’t it be nice to have a short, fairly efficient, rapidly deployable, low visual impact, vertical antenna that can be operated on both the 20 meter and 40 meter bands? The 2B2L (2 Band Linear Loaded) antenna comes very close to a perfect match for those specifications.

The 2B2L is the brainchild of Tim KQ4TQ who pitched the idea to me in an email recently. Seeing the potential in Tim’s idea, I hastily built a prototype and erected it in my backyard for testing. The 2B2L is based on the “Simple Ladder Line Antenna for Portable Ops” discussed a couple of weeks ago here on Ham Radio Outside the Box. But here is the genius in the 2 band version: by adding a loading coil and a tail section – also made from ladder line – to the top of the original single band (20m) version, we can add the 40m band. The whole antenna towers up to the dizzying height of just 15 feet!

But, just a moment; before the grey-haired, white-coated men with a physics diploma hanging on the wall pick up their quill pens to denounce the 2B2L, a confession is in order. Yes, admittedly, the 2B2L is not perfect; field portable antennas rarely are perfect. Those of us who like to operate out in the Big Blue Sky Shack must necessarily accept some compromises. Those of us who like to operate QRP accept even more compromises. So where’s the gotcha?

The loading coil for the 40m extension is the weak link. It serves two purposes: (1) it acts as an RF choke for the lower 20m band section; it’s high impedance effectively terminates the lower section of the antenna so that the top section does not affect operation on 20 meters; (2) it acts as a loading coil for the 40 meter top section which is considerably shortened as a result. But is it actually all bad? Yes, it has some loss due to the i^2R effect, but consider this: the whole antenna is radiating on 40 meters and the coil is near the top where the current is lower. If I am thinking with half a brain here please correct me in the comments. I did once think I was wrong, but I was mistaken!

Can an antenna that is only 15 feet tall really be efficient on 20m and 40m? The secret to how it can claim enough efficiency to actually make contacts out in the field lies in its use of linear loaded elements. Two sections of ladder line, each shorted at the top, provide the linear loading which shortens the required length by about 30%. Linear loading is considered one of the most efficient ways of shortening an antenna.

Also, the 2B2L is mounted quite close to the ground which inevitably diverts some RF to warming the earthworms. Mine is fed about 12 inches (~30 cm) above ground. It could also be raised higher and used with tuned, raised radials, but on 40 meters the radials would each be around 33 feet long. I chose to use short ground radials instead.

Where to buy a 2B2L?

Sorry folks, this is another real hobbyist’s project – you gotta build it yourself. You’re going to need some ladder line from whatever source you go to for ham radio supplies. Mine was a generous gift from my friend and CW buddy Mary VE3MVM. You will also need a coil. I had an air core coil lying in the drawer from a previous project. I built it using a a short section of PVC tubing about 2 inches (5 cm) in diameter. You will need an inductance meter, or a NanoVNA, to measure the inductance. As a purely rough guide, my coil has 35 turns of 20 awg stranded insulated wire. Here is the materials list:

• 11.5 feet (3.5 meters) of ladder line for the 20 meter radiating element
• 38 inches (0.97 meters) of ladder line for the 40 meter extension
• 35 microhenry coil

Setting up the 2B2L antenna

The 2B2L can be erected on a pole about 16 feet (or about 5 meters) tall. It is fed at the bottom via coax to a transceiver. The 2B2L requires radials. I tried a set of 8 radials, each 7 feet (2 meters) long. That worked but 4 radials, each 13 feet long provided a better return path on 40 meters.

In keeping with recent practise here on Ham Radio Outside the Box, the radials are tuned with a GTU (Ground Tuning Unit). The GTU has to be separately adjusted for each of the two bands. This ensures that the antenna system is working as efficiently as possible – without a tuner! An antenna analyzer connected via a short coax showed an SWR well below 1.5 could be obtained on both bands.

Does it QSO?

No, it just sits there grinning at the sky, but I have QSO’d using the 2B2L. My best contact so far has been a 2000 kilometer QSO with a station in Colorado on 20 meters by QRP CW. 40 meters is most active in the early morning and in the evening when I am inactive, but I am going to have to make the effort to go 40 meter QSO hunting real soon. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

TechTip #2: Observe the polarity of a GTU!

This is the second in an occasional series of short posts that zero in on details of a specific technical topic in relation to projects here on this blog, which some readers may find helpful.

A few weeks Ham Radio Outside the Box published a description of a “Mini Ground Tuning Unit (GTU)”. The schematic for that device is reproduced below. The design was then simplified with input from HROTB-Labs collaborator Tim KQ4TQ. Tim proposed a single inductance with a value of 3 microhenries (and generously donated a prototype he had built).

I built the revised GTU and performed many experiments in HROTB-Labs outdoor test facility (actually, my backyard). Various types of ground planes were tried, from G4AKC’s capacitance plate at the base of his pedestrian mobile radio trolley, to Faraday cloth (“magic carpet”), to ground radials.

My least favorite was the Faraday cloth. The one I used was about 1 square meter in area. I acknowledge the input of Paul VE3PVB who emphasized the need to maximize the area of the Faraday cloth to improve its efficiency. Two things about Faraday cloth are worth noting: first it has a shiny surface which can be distractingly reflective in bright sunshine. Second, it is often referred to as “magic carpet” – a very appropriate term since it has a tendency to fly in even a mild wind. Matt finish paint and a bag of rocks fixes both issues.

I settled on a set of 8 short radials (each 7 feet, or 2 meters long) and they work well. A single long radial wire might be more convenient for rapid deployment in the field. Along with the Ground Tuning Unit (GTU) and a resonant vertical radiating element, a very acceptable SWR is obtained without the use of a tuner.

But back to the GTU and the topic of this TechTip. I tend to rush my projects. Bad! I inadvertently wired my GTU back to front. The result was a significant hand capacitance effect which made precise adjustment of the GTU a little tricky. I had connected the counterpoise (radial wires) to the variable capacitor end of the GTU instead of the inductor end. The result was that, as I adjusted the variable capacitor, my hand was close to the high impedance side of the GTU and became part of the counterpoise.

The fix

I reversed the connections to comply with the circuit schematic (above) and the situation improved but is not entirely resolved. My GTU layout still brings my hand in close proximity to the terminal where the counterpoise is attached and so the GTU will have to be rebuilt to fix that too. So, if you decide to build your own GTU it would be a good idea to (1) carefully observe the polarity according to the schematic shown above, and (2) keep the layout simple to minimize hand capacitance.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

TechTip #2: Observe the polarity of a GTU!

This is the second in an occasional series of short posts that zero in on details of a specific technical topic in relation to projects here on this blog, which some readers may find helpful.

A few weeks Ham Radio Outside the Box published a description of a “Mini Ground Tuning Unit (GTU)”. The schematic for that device is reproduced below. The design was then simplified with input from HROTB-Labs collaborator Tim KQ4TQ. Tim proposed a single inductance with a value of 3 microhenries (and generously donated a prototype he had built).

I built the revised GTU and performed many experiments in HROTB-Labs outdoor test facility (actually, my backyard). Various types of ground planes were tried, from G4AKC’s capacitance plate at the base of his pedestrian mobile radio trolley, to Faraday cloth (“magic carpet”), to ground radials.

My least favorite was the Faraday cloth. The one I used was about 1 square meter in area. I acknowledge the input of Paul VE3PVB who emphasized the need to maximize the area of the Faraday cloth to improve its efficiency. Two things about Faraday cloth are worth noting: first it has a shiny surface which can be distractingly reflective in bright sunshine. Second, it is often referred to as “magic carpet” – a very appropriate term since it has a tendency to fly in even a mild wind. Matt finish paint and a bag of rocks fixes both issues.

I settled on a set of 8 short radials (each 7 feet, or 2 meters long) and they work well. A single long radial wire might be more convenient for rapid deployment in the field. Along with the Ground Tuning Unit (GTU) and a resonant vertical radiating element, a very acceptable SWR is obtained without the use of a tuner.

But back to the GTU and the topic of this TechTip. I tend to rush my projects. Bad! I inadvertently wired my GTU back to front. The result was a significant hand capacitance effect which made precise adjustment of the GTU a little tricky. I had connected the counterpoise (radial wires) to the variable capacitor end of the GTU instead of the inductor end. The result was that, as I adjusted the variable capacitor, my hand was close to the high impedance side of the GTU and became part of the counterpoise.

The fix

I reversed the connections to comply with the circuit schematic (above) and the situation improved but is not entirely resolved. My GTU layout still brings my hand in close proximity to the terminal where the counterpoise is attached and so the GTU will have to be rebuilt to fix that too. So, if you decide to build your own GTU it would be a good idea to (1) carefully observe the polarity according to the schematic shown above, and (2) keep the layout simple to minimize hand capacitance.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Simple Ladder Line Antenna for Portable Ops

For the last several weeks I have been experimenting with ideas for low impact field antennas that optimize stealth, rapid deployment and small footprint while maintaining efficiency. It’s a trade-off between size, portability and efficiency. The antenna that is very small, highly portable and very efficient hasn’t been invented yet – and never will be invented because it would defy the laws of physics.

Some hams may hold the belief that a short, base-loaded whip defies physics because (1) it can be tuned to 1:1 SWR, and (2) it can be used to make contacts. On the right day, under favorable propagation conditions even a wet noodle makes a “great antenna”. I have personally made contacts with a dummy load (across a room during a technical presentation). A 1:1 SWR ensures a transceiver won’t release the “magic smoke”; it does not make a poor antenna work any better.

Oh yes, I’m the great pretender …

The Platters (love those songs) could have been singing about ham radio tuners. Internal tuners, or any tuner located at the radio end of a feedline is a great pretender. It pretends the antenna is doing well when really its only job is to convert the impedance of the antenna, and feedline, into something that won’t vaporize those little 3-legged fuses that we like to call PA transistors in the transceiver.

For this reason I prefer to avoid using a “tuner” at the radio end of the feedline. A tuner has a role to play when using a multiband antenna (such as a random wire), but a monoband antenna can be adjusted to resonance (or close to resonance) thereby avoiding any need for an impedance transformation at the radio end of a short feedline. For example, a simple resonant whip mounted on a pole a couple of meters above ground, with two or more resonant radial wires does not require a tuner. But there’s a gotcha.

High wire act – danger, danger!

I was playing radio in a provincial park once when my wobbly whip attracted the attention of a patrolling park warden. Her job included preventing mad boffins with dubious aerial erections from endangering other park users. I was able to persuade her that my activities were unlikely to trigger the arrival of emergency services and all was well. That experience convinced me of the value of operating stealthily by staying under the radar of anybody who may look on my activities with suspicion. Lesson learned – low antennas equal low attention.

The Dancing Queen

I have told the tale of the dancing lady several times on Ham Radio Outside the Box. My unusual activity attracted her attraction and she approached to inquire what I was doing. When I advised her to be careful of the long radial wires on the ground she broke into an impromptu and erratic dance routine. Lesson learned – long radials are where angels fear to tread.

When the twilight is gone, and no songbirds are singing …

My wife and I have been putting out bird feeders in our back yard for quite some time. The feeders have attracted many different kinds of birds, prompting us to learn more about their behavior and habitat. One of the important things we learned is that trees are birds’ safe place. It is where they shelter and nest. Lesson learned – avoid invading their space by firing projectiles and dragging long wires through it.

Park wardens licking their pencils ready to write out an infraction ticket, dancing queens dodging wiggly wires, and fishing weights landing in bird nests … by all the ancient Norse gods, what’s a poor ham to do? Those were the design parameters I had to work with. Could it be done? Could I design antenna that will fit into those restrictions? The Devil was dangling a short base-loaded whip in front of my eyes but I banished him. No, that is not the solution!

So what is the solution?

There are inevitably many solutions to this puzzling conundrum and each may work in some fashion. One contender is something I have come up with and called a “Ladder Line Antenna”. Ladder Line (sometimes referred to as “Window Line”) is usually used as a feedline but it doesn’t have to be so. Ladder Line is simply two conductors separated by plastic with a series of rectangular holes. It resembles a ladder, or looked at differently, it could be seen as a series of windows.

Why use Ladder Line as the antenna’s radiator? Because, to reduce the overall height of the antenna by around 30% the antenna is linear-loaded. Linear loading is the technique of folding back the radiating element and can be achieved by shorting the two ladder line conductors at the top. The far end of the folded side of the radiator is left unconnected. The radiator is connected to the coax center conductor.

The overall length of the Ladder Line radiating element for my 20m band antenna is approximately eleven and a half feet (three and a half meters). It was trimmed while measuring its electrical length with an antenna analyzer.

Banishing the Dancing Queen

Understanding that long radials for this antenna are strictly verboten creates a bit of a problem. Usually, a set of ground mounted radial wires are employed with a vertical antenna and a tuner is used at the radio end of the feedline to match the impedance.

No matter how many radials are laid down they will not be resonant. And, the use of a tuner has been ruled to be equally verboten. But there is a solution and that is to use a GTU (Ground Tuning Unit) to increase the current in the radial system, making it appear resonant. To keep the Dancing Queen at bay I shortened the radial wire length to 7 feet (a little over 2 meters) and used eight radials. The radiating element has already been adjusted for resonance so now is the overall antenna resonant? Well not quite.

You can’t cheat physics. Eight short radials, even when “tuned” with a GTU are not resonant. My experiments with a square meter of Faraday cloth proved that principle. There remains a small reactive component to the antenna impedance as can be seen in this image of the antenna analyzer reading when connected by a very short length of coax.

The reactive component, in this case 5.43 ohms of capacitive reactance, could have been reduced further by careful adjustment of the GTU. Unfortunately, the GTU is difficult to adjust precisely and hand capacitance also affects the adjustment. Another challenge for brainy boffins to overcome. The impossible done at once, miracles take a little longer!

Is a linear loaded antenna efficient?

L.B. Cebik W4RNL(SK) published a series of articles on shortening HF dipoles. He established that dipoles remain quite efficient down to 10% of their full length. However, below 70% the complex impedance becomes increasingly difficult to match. My simple ladder line antenna is shortened to approximately 70% of its original length.

The real world test

Following several sessions out in my backyard, hunting POTA stations, I figured the antenna was ready for the real test. Could it work well enough for a QRP CW POTA activation?

I had two activations planned, each in separate locations. During the first activation, propagation conditions were a little difficult with a lot of signal fading (QSB). Stations would disappear into the noise then, seconds later, come back bending the needle on the signal strength meter. It took an hour to log 13 stations, but with the furthest being 1876 km away it showed the short, low profile antenna had good potential.

The second activation a few days later showed even better results.

Propagation conditions were better this time around and contacts were made in Arizona, nearly 3000 km away from my QTH on the Canadian shoreline of Lake Huron, Colorado (2200 km) and several others close to 2000 km. It was also interesting to note that some of the contacts made were less than 1000km away. This means the antenna is capable of radiating signals at a broad range of take-off angles.

Overall I am very pleased with this simple, low profile antenna. It can be supported on a very lightweight 13 ft high pole that mounts on a small stake in the ground in summer, or a compact tripod when the ground is frozen in winter. The eight 7 feet long radials take the longest to deploy and occupy a circular footprint of 14 feet. An alternative I am working on involves a single raised linear loaded radial to replace the ground radials. This will reduce the footprint to two dimensions and make the antenna suitable for deployment on a narrow trail. I am also working on a multi-band version of this antenna. More details to follow in a future post; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Simple Ladder Line Antenna for Portable Ops

For the last several weeks I have been experimenting with ideas for low impact field antennas that optimize stealth, rapid deployment and small footprint while maintaining efficiency. It’s a trade-off between size, portability and efficiency. The antenna that is very small, highly portable and very efficient hasn’t been invented yet – and never will be invented because it would defy the laws of physics.

Some hams may hold the belief that a short, base-loaded whip defies physics because (1) it can be tuned to 1:1 SWR, and (2) it can be used to make contacts. On the right day, under favorable propagation conditions even a wet noodle makes a “great antenna”. I have personally made contacts with a dummy load (across a room during a technical presentation). A 1:1 SWR ensures a transceiver won’t release the “magic smoke”; it does not make a poor antenna work any better.

Oh yes, I’m the great pretender …

The Platters (love those songs) could have been singing about ham radio tuners. Internal tuners, or any tuner located at the radio end of a feedline is a great pretender. It pretends the antenna is doing well when really its only job is to convert the impedance of the antenna, and feedline, into something that won’t vaporize those little 3-legged fuses that we like to call PA transistors in the transceiver.

For this reason I prefer to avoid using a “tuner” at the radio end of the feedline. A tuner has a role to play when using a multiband antenna (such as a random wire), but a monoband antenna can be adjusted to resonance (or close to resonance) thereby avoiding any need for an impedance transformation at the radio end of a short feedline. For example, a simple resonant whip mounted on a pole a couple of meters above ground, with two or more resonant radial wires does not require a tuner. But there’s a gotcha.

High wire act – danger, danger!

I was playing radio in a provincial park once when my wobbly whip attracted the attention of a patrolling park warden. Her job included preventing mad boffins with dubious aerial erections from endangering other park users. I was able to persuade her that my activities were unlikely to trigger the arrival of emergency services and all was well. That experience convinced me of the value of operating stealthily by staying under the radar of anybody who may look on my activities with suspicion. Lesson learned – low antennas equal low attention.

The Dancing Queen

I have told the tale of the dancing lady several times on Ham Radio Outside the Box. My unusual activity attracted her attraction and she approached to inquire what I was doing. When I advised her to be careful of the long radial wires on the ground she broke into an impromptu and erratic dance routine. Lesson learned – long radials are where angels fear to tread.

When the twilight is gone, and no songbirds are singing …

My wife and I have been putting out bird feeders in our back yard for quite some time. The feeders have attracted many different kinds of birds, prompting us to learn more about their behavior and habitat. One of the important things we learned is that trees are birds’ safe place. It is where they shelter and nest. Lesson learned – avoid invading their space by firing projectiles and dragging long wires through it.

Park wardens licking their pencils ready to write out an infraction ticket, dancing queens dodging wiggly wires, and fishing weights landing in bird nests … by all the ancient Norse gods, what’s a poor ham to do? Those were the design parameters I had to work with. Could it be done? Could I design antenna that will fit into those restrictions? The Devil was dangling a short base-loaded whip in front of my eyes but I banished him. No, that is not the solution!

So what is the solution?

There are inevitably many solutions to this puzzling conundrum and each may work in some fashion. One contender is something I have come up with and called a “Ladder Line Antenna”. Ladder Line (sometimes referred to as “Window Line”) is usually used as a feedline but it doesn’t have to be so. Ladder Line is simply two conductors separated by plastic with a series of rectangular holes. It resembles a ladder, or looked at differently, it could be seen as a series of windows.

Why use Ladder Line as the antenna’s radiator? Because, to reduce the overall height of the antenna by around 30% the antenna is linear-loaded. Linear loading is the technique of folding back the radiating element and can be achieved by shorting the two ladder line conductors at the top. The far end of the folded side of the radiator is left unconnected. The radiator is connected to the coax center conductor.

The overall length of the Ladder Line radiating element for my 20m band antenna is approximately eleven and a half feet (three and a half meters). It was trimmed while measuring its electrical length with an antenna analyzer.

Banishing the Dancing Queen

Understanding that long radials for this antenna are strictly verboten creates a bit of a problem. Usually, a set of ground mounted radial wires are employed with a vertical antenna and a tuner is used at the radio end of the feedline to match the impedance.

No matter how many radials are laid down they will not be resonant. And, the use of a tuner has been ruled to be equally verboten. But there is a solution and that is to use a GTU (Ground Tuning Unit) to increase the current in the radial system, making it appear resonant. To keep the Dancing Queen at bay I shortened the radial wire length to 7 feet (a little over 2 meters) and used eight radials. The radiating element has already been adjusted for resonance so now is the overall antenna resonant? Well not quite.

You can’t cheat physics. Eight short radials, even when “tuned” with a GTU are not resonant. My experiments with a square meter of Faraday cloth proved that principle. There remains a small reactive component to the antenna impedance as can be seen in this image of the antenna analyzer reading when connected by a very short length of coax.

The reactive component, in this case 5.43 ohms of capacitive reactance, could have been reduced further by careful adjustment of the GTU. Unfortunately, the GTU is difficult to adjust precisely and hand capacitance also affects the adjustment. Another challenge for brainy boffins to overcome. The impossible done at once, miracles take a little longer!

Is a linear loaded antenna efficient?

L.B. Cebik W4RNL(SK) published a series of articles on shortening HF dipoles. He established that dipoles remain quite efficient down to 10% of their full length. However, below 70% the complex impedance becomes increasingly difficult to match. My simple ladder line antenna is shortened to approximately 70% of its original length.

The real world test

Following several sessions out in my backyard, hunting POTA stations, I figured the antenna was ready for the real test. Could it work well enough for a QRP CW POTA activation?

I had two activations planned, each in separate locations. During the first activation, propagation conditions were a little difficult with a lot of signal fading (QSB). Stations would disappear into the noise then, seconds later, come back bending the needle on the signal strength meter. It took an hour to log 13 stations, but with the furthest being 1876 km away it showed the short, low profile antenna had good potential.

The second activation a few days later showed even better results.

Propagation conditions were better this time around and contacts were made in Arizona, nearly 3000 km away from my QTH on the Canadian shoreline of Lake Huron, Colorado (2200 km) and several others close to 2000 km. It was also interesting to note that some of the contacts made were less than 1000km away. This means the antenna is capable of radiating signals at a broad range of take-off angles.

Overall I am very pleased with this simple, low profile antenna. It can be supported on a very lightweight 13 ft high pole that mounts on a small stake in the ground in summer, or a compact tripod when the ground is frozen in winter. The eight 7 feet long radials take the longest to deploy and occupy a circular footprint of 14 feet. An alternative I am working on involves a single raised linear loaded radial to replace the ground radials. This will reduce the footprint to two dimensions and make the antenna suitable for deployment on a narrow trail. I am also working on a multi-band version of this antenna. More details to follow in a future post; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Simple Ladder Line Antenna for Portable Ops

For the last several weeks I have been experimenting with ideas for low impact field antennas that optimize stealth, rapid deployment and small footprint while maintaining efficiency. It’s a trade-off between size, portability and efficiency. The antenna that is very small, highly portable and very efficient hasn’t been invented yet – and never will be invented because it would defy the laws of physics.

Some hams may hold the belief that a short, base-loaded whip defies physics because (1) it can be tuned to 1:1 SWR, and (2) it can be used to make contacts. On the right day, under favorable propagation conditions even a wet noodle makes a “great antenna”. I have personally made contacts with a dummy load (across a room during a technical presentation). A 1:1 SWR ensures a transceiver won’t release the “magic smoke”; it does not make a poor antenna work any better.

Oh yes, I’m the great pretender …

The Platters (love those songs) could have been singing about ham radio tuners. Internal tuners, or any tuner located at the radio end of a feedline is a great pretender. It pretends the antenna is doing well when really its only job is to convert the impedance of the antenna, and feedline, into something that won’t vaporize those little 3-legged fuses that we like to call PA transistors in the transceiver.

For this reason I prefer to avoid using a “tuner” at the radio end of the feedline. A tuner has a role to play when using a multiband antenna (such as a random wire), but a monoband antenna can be adjusted to resonance (or close to resonance) thereby avoiding any need for an impedance transformation at the radio end of a short feedline. For example, a simple resonant whip mounted on a pole a couple of meters above ground, with two or more resonant radial wires does not require a tuner. But there’s a gotcha.

High wire act – danger, danger!

I was playing radio in a provincial park once when my wobbly whip attracted the attention of a patrolling park warden. Her job included preventing mad boffins with dubious aerial erections from endangering other park users. I was able to persuade her that my activities were unlikely to trigger the arrival of emergency services and all was well. That experience convinced me of the value of operating stealthily by staying under the radar of anybody who may look on my activities with suspicion. Lesson learned – low antennas equal low attention.

The Dancing Queen

I have told the tale of the dancing lady several times on Ham Radio Outside the Box. My unusual activity attracted her attraction and she approached to inquire what I was doing. When I advised her to be careful of the long radial wires on the ground she broke into an impromptu and erratic dance routine. Lesson learned – long radials are where angels fear to tread.

When the twilight is gone, and no songbirds are singing …

My wife and I have been putting out bird feeders in our back yard for quite some time. The feeders have attracted many different kinds of birds, prompting us to learn more about their behavior and habitat. One of the important things we learned is that trees are birds’ safe place. It is where they shelter and nest. Lesson learned – avoid invading their space by firing projectiles and dragging long wires through it.

Park wardens licking their pencils ready to write out an infraction ticket, dancing queens dodging wiggly wires, and fishing weights landing in bird nests … by all the ancient Norse gods, what’s a poor ham to do? Those were the design parameters I had to work with. Could it be done? Could I design antenna that will fit into those restrictions? The Devil was dangling a short base-loaded whip in front of my eyes but I banished him. No, that is not the solution!

So what is the solution?

There are inevitably many solutions to this puzzling conundrum and each may work in some fashion. One contender is something I have come up with and called a “Ladder Line Antenna”. Ladder Line (sometimes referred to as “Window Line”) is usually used as a feedline but it doesn’t have to be so. Ladder Line is simply two conductors separated by plastic with a series of rectangular holes. It resembles a ladder, or looked at differently, it could be seen as a series of windows.

Why use Ladder Line as the antenna’s radiator? Because, to reduce the overall height of the antenna by around 30% the antenna is linear-loaded. Linear loading is the technique of folding back the radiating element and can be achieved by shorting the two ladder line conductors at the top. The far end of the folded side of the radiator is left unconnected. The radiator is connected to the coax center conductor.

The overall length of the Ladder Line radiating element for my 20m band antenna is approximately eleven and a half feet (three and a half meters). It was trimmed while measuring its electrical length with an antenna analyzer.

Banishing the Dancing Queen

Understanding that long radials for this antenna are strictly verboten creates a bit of a problem. Usually, a set of ground mounted radial wires are employed with a vertical antenna and a tuner is used at the radio end of the feedline to match the impedance.

No matter how many radials are laid down they will not be resonant. And, the use of a tuner has been ruled to be equally verboten. But there is a solution and that is to use a GTU (Ground Tuning Unit) to increase the current in the radial system, making it appear resonant. To keep the Dancing Queen at bay I shortened the radial wire length to 7 feet (a little over 2 meters) and used eight radials. The radiating element has already been adjusted for resonance so now is the overall antenna resonant? Well not quite.

You can’t cheat physics. Eight short radials, even when “tuned” with a GTU are not resonant. My experiments with a square meter of Faraday cloth proved that principle. There remains a small reactive component to the antenna impedance as can be seen in this image of the antenna analyzer reading when connected by a very short length of coax.

The reactive component, in this case 5.43 ohms of capacitive reactance, could have been reduced further by careful adjustment of the GTU. Unfortunately, the GTU is difficult to adjust precisely and hand capacitance also affects the adjustment. Another challenge for brainy boffins to overcome. The impossible done at once, miracles take a little longer!

Is a linear loaded antenna efficient?

L.B. Cebik W4RNL(SK) published a series of articles on shortening HF dipoles. He established that dipoles remain quite efficient down to 10% of their full length. However, below 70% the complex impedance becomes increasingly difficult to match. My simple ladder line antenna is shortened to approximately 70% of its original length.

The real world test

Following several sessions out in my backyard, hunting POTA stations, I figured the antenna was ready for the real test. Could it work well enough for a QRP CW POTA activation?

I had two activations planned, each in separate locations. During the first activation, propagation conditions were a little difficult with a lot of signal fading (QSB). Stations would disappear into the noise then, seconds later, come back bending the needle on the signal strength meter. It took an hour to log 13 stations, but with the furthest being 1876 km away it showed the short, low profile antenna had good potential.

The second activation a few days later showed even better results.

Propagation conditions were better this time around and contacts were made in Arizona, nearly 3000 km away from my QTH on the Canadian shoreline of Lake Huron, Colorado (2200 km) and several others close to 2000 km. It was also interesting to note that some of the contacts made were less than 1000km away. This means the antenna is capable of radiating signals at a broad range of take-off angles.

Overall I am very pleased with this simple, low profile antenna. It can be supported on a very lightweight 13 ft high pole that mounts on a small stake in the ground in summer, or a compact tripod when the ground is frozen in winter. The eight 7 feet long radials take the longest to deploy and occupy a circular footprint of 14 feet. An alternative I am working on involves a single raised linear loaded radial to replace the ground radials. This will reduce the footprint to two dimensions and make the antenna suitable for deployment on a narrow trail. I am also working on a multi-band version of this antenna. More details to follow in a future post; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Simple Ladder Line Antenna for Portable Ops

For the last several weeks I have been experimenting with ideas for low impact field antennas that optimize stealth, rapid deployment and small footprint while maintaining efficiency. It’s a trade-off between size, portability and efficiency. The antenna that is very small, highly portable and very efficient hasn’t been invented yet – and never will be invented because it would defy the laws of physics.

Some hams may hold the belief that a short, base-loaded whip defies physics because (1) it can be tuned to 1:1 SWR, and (2) it can be used to make contacts. On the right day, under favorable propagation conditions even a wet noodle makes a “great antenna”. I have personally made contacts with a dummy load (across a room during a technical presentation). A 1:1 SWR ensures a transceiver won’t release the “magic smoke”; it does not make a poor antenna work any better.

Oh yes, I’m the great pretender …

The Platters (love those songs) could have been singing about ham radio tuners. Internal tuners, or any tuner located at the radio end of a feedline is a great pretender. It pretends the antenna is doing well when really its only job is to convert the impedance of the antenna, and feedline, into something that won’t vaporize those little 3-legged fuses that we like to call PA transistors in the transceiver.

For this reason I prefer to avoid using a “tuner” at the radio end of the feedline. A tuner has a role to play when using a multiband antenna (such as a random wire), but a monoband antenna can be adjusted to resonance (or close to resonance) thereby avoiding any need for an impedance transformation at the radio end of a short feedline. For example, a simple resonant whip mounted on a pole a couple of meters above ground, with two or more resonant radial wires does not require a tuner. But there’s a gotcha.

High wire act – danger, danger!

I was playing radio in a provincial park once when my wobbly whip attracted the attention of a patrolling park warden. Her job included preventing mad boffins with dubious aerial erections from endangering other park users. I was able to persuade her that my activities were unlikely to trigger the arrival of emergency services and all was well. That experience convinced me of the value of operating stealthily by staying under the radar of anybody who may look on my activities with suspicion. Lesson learned – low antennas equal low attention.

The Dancing Queen

I have told the tale of the dancing lady several times on Ham Radio Outside the Box. My unusual activity attracted her attraction and she approached to inquire what I was doing. When I advised her to be careful of the long radial wires on the ground she broke into an impromptu and erratic dance routine. Lesson learned – long radials are where angels fear to tread.

When the twilight is gone, and no songbirds are singing …

My wife and I have been putting out bird feeders in our back yard for quite some time. The feeders have attracted many different kinds of birds, prompting us to learn more about their behavior and habitat. One of the important things we learned is that trees are birds’ safe place. It is where they shelter and nest. Lesson learned – avoid invading their space by firing projectiles and dragging long wires through it.

Park wardens licking their pencils ready to write out an infraction ticket, dancing queens dodging wiggly wires, and fishing weights landing in bird nests … by all the ancient Norse gods, what’s a poor ham to do? Those were the design parameters I had to work with. Could it be done? Could I design antenna that will fit into those restrictions? The Devil was dangling a short base-loaded whip in front of my eyes but I banished him. No, that is not the solution!

So what is the solution?

There are inevitably many solutions to this puzzling conundrum and each may work in some fashion. One contender is something I have come up with and called a “Ladder Line Antenna”. Ladder Line (sometimes referred to as “Window Line”) is usually used as a feedline but it doesn’t have to be so. Ladder Line is simply two conductors separated by plastic with a series of rectangular holes. It resembles a ladder, or looked at differently, it could be seen as a series of windows.

Why use Ladder Line as the antenna’s radiator? Because, to reduce the overall height of the antenna by around 30% the antenna is linear-loaded. Linear loading is the technique of folding back the radiating element and can be achieved by shorting the two ladder line conductors at the top. The far end of the folded side of the radiator is left unconnected. The radiator is connected to the coax center conductor.

The overall length of the Ladder Line radiating element for my 20m band antenna is approximately eleven and a half feet (three and a half meters). It was trimmed while measuring its electrical length with an antenna analyzer.

Banishing the Dancing Queen

Understanding that long radials for this antenna are strictly verboten creates a bit of a problem. Usually, a set of ground mounted radial wires are employed with a vertical antenna and a tuner is used at the radio end of the feedline to match the impedance.

No matter how many radials are laid down they will not be resonant. And, the use of a tuner has been ruled to be equally verboten. But there is a solution and that is to use a GTU (Ground Tuning Unit) to increase the current in the radial system, making it appear resonant. To keep the Dancing Queen at bay I shortened the radial wire length to 7 feet (a little over 2 meters) and used eight radials. The radiating element has already been adjusted for resonance so now is the overall antenna resonant? Well not quite.

You can’t cheat physics. Eight short radials, even when “tuned” with a GTU are not resonant. My experiments with a square meter of Faraday cloth proved that principle. There remains a small reactive component to the antenna impedance as can be seen in this image of the antenna analyzer reading when connected by a very short length of coax.

The reactive component, in this case 5.43 ohms of capacitive reactance, could have been reduced further by careful adjustment of the GTU. Unfortunately, the GTU is difficult to adjust precisely and hand capacitance also affects the adjustment. Another challenge for brainy boffins to overcome. The impossible done at once, miracles take a little longer!

Is a linear loaded antenna efficient?

L.B. Cebik W4RNL(SK) published a series of articles on shortening HF dipoles. He established that dipoles remain quite efficient down to 10% of their full length. However, below 70% the complex impedance becomes increasingly difficult to match. My simple ladder line antenna is shortened to approximately 70% of its original length.

The real world test

Following several sessions out in my backyard, hunting POTA stations, I figured the antenna was ready for the real test. Could it work well enough for a QRP CW POTA activation?

I had two activations planned, each in separate locations. During the first activation, propagation conditions were a little difficult with a lot of signal fading (QSB). Stations would disappear into the noise then, seconds later, come back bending the needle on the signal strength meter. It took an hour to log 13 stations, but with the furthest being 1876 km away it showed the short, low profile antenna had good potential.

The second activation a few days later showed even better results.

Propagation conditions were better this time around and contacts were made in Arizona, nearly 3000 km away from my QTH on the Canadian shoreline of Lake Huron, Colorado (2200 km) and several others close to 2000 km. It was also interesting to note that some of the contacts made were less than 1000km away. This means the antenna is capable of radiating signals at a broad range of take-off angles.

Overall I am very pleased with this simple, low profile antenna. It can be supported on a very lightweight 13 ft high pole that mounts on a small stake in the ground in summer, or a compact tripod when the ground is frozen in winter. The eight 7 feet long radials take the longest to deploy and occupy a circular footprint of 14 feet. An alternative I am working on involves a single raised linear loaded radial to replace the ground radials. This will reduce the footprint to two dimensions and make the antenna suitable for deployment on a narrow trail. I am also working on a multi-band version of this antenna. More details to follow in a future post; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

So I'm new to the world of #antennas and radio calibrations and from what I understand the #meshtastic ranges are supposed to run in the 915 megahertz range for the US, not 868. Though I also see 906MHz as the auto calculated range in the app, so is this just the floor for this antenna and it does support 915MHz?

So I'm new to the world of #antennas and radio calibrations and from what I understand the #meshtastic ranges are supposed to run in the 915 megahertz range for the US, not 868. Though Thoughts also see opt as the auto calculated range in the app, so is this just the floor for this antenna and it foes support 915MHz?

TechTip#1 – a continuous loop of cordage

This is the first in an occasional series of short posts here on Ham Radio Outside the Box. The purpose of these TechTips is to share useful techniques I have learned over the years. I hope you will find them helpful.

TechTip#1 is an idea I picked up from a bushcraft video for creating a continuous loop of cordage. Of course, it is very easy to create a loop of cordage by simply tying the ends together with a knot. But that can be untidy and inconvenient, especially if the knot gets in the way of a neat join between two components of, for example, an antenna system.

How to use a continuous loop?

I use them a lot when erecting portable antennas. For example, if a cow hitch is formed at one end of the loop and a knot is tied at the end of a radial wire, the cow hitch can grip the wire end very securely – as long as tension is maintained in the loop. A second cow hitch can be formed at the other end of the loop to attach it to a tent stake. To release the wire simply pull out the tent stake, which relieves the tension and the wire is free.

Creating a continuous loop is surprisingly easy to do in just 3 simple steps.

STEP 1

Cut a length of thin cordage about 18 inches (46 cm) long. I use Atwood 1/16 inch (1.6 mm) Utility Rope, but any similar cordage, such as Bank Line, will do.

STEP 2

This is a very important step! Make sure both ends of the cordage are freshly cut, then melt the ends with a barbeque lighter, or similar. While the ends are still very hot press them gently together to form a bond. Be careful with this step because melted cordage can be quite painful if it gets on your hands. Being an amateur masochist I wait a couple of seconds then roll the join between two fingers to smooth the finished bond.

STEP 3

When the join has cooled – after just a few seconds – grab the loop either side of the join and pull like hell to test it. I was skeptical at first, but I can pull as hard as I like without breaking the bond. The Atwood cordage I use has a breaking strain of 110 lb (50 kg) and I suspect the join has the same strength.

If you have any similar amateur radio tips to share please send them to me via email, with photos if available and your tip will be featured here in a future Ham Radio Outside the Box TechTip.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

TechTip#1 – a continuous loop of cordage

This is the first in an occasional series of short posts here on Ham Radio Outside the Box. The purpose of these TechTips is to share useful techniques I have learned over the years. I hope you will find them helpful.

TechTip#1 is an idea I picked up from a bushcraft video for creating a continuous loop of cordage. Of course, it is very easy to create a loop of cordage by simply tying the ends together with a knot. But that can be untidy and inconvenient, especially if the knot gets in the way of a neat join between two components of, for example, an antenna system.

How to use a continuous loop?

I use them a lot when erecting portable antennas. For example, if a cow hitch is formed at one end of the loop and a knot is tied at the end of a radial wire, the cow hitch can grip the wire end very securely – as long as tension is maintained in the loop. A second cow hitch can be formed at the other end of the loop to attach it to a tent stake. To release the wire simply pull out the tent stake, which relieves the tension and the wire is free.

Creating a continuous loop is surprisingly easy to do in just 3 simple steps.

STEP 1

Cut a length of thin cordage about 18 inches (46 cm) long. I use Atwood 1/16 inch (1.6 mm) Utility Rope, but any similar cordage, such as Bank Line, will do.

STEP 2

This is a very important step! Make sure both ends of the cordage are freshly cut, then melt the ends with a barbeque lighter, or similar. While the ends are still very hot press them gently together to form a bond. Be careful with this step because melted cordage can be quite painful if it gets on your hands. Being an amateur masochist I wait a couple of seconds then roll the join between two fingers to smooth the finished bond.

STEP 3

When the join has cooled – after just a few seconds – grab the loop either side of the join and pull like hell to test it. I was skeptical at first, but I can pull as hard as I like without breaking the bond. The Atwood cordage I use has a breaking strain of 110 lb (50 kg) and I suspect the join has the same strength.

If you have any similar amateur radio tips to share please send them to me via email, with photos if available and your tip will be featured here in a future Ham Radio Outside the Box TechTip.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A road trip with the VP2E antenna … and wolves

My wife and I recently took a short early summer vacation in the Haliburton Highlands area of Ontario. The area is just south-west of Algonquin Park (Ontario’s first and by far the largest provincial park, most of which is accessible only by canoe with sometimes very long and challenging portages … and with a very large population of black bears and wolves).

I had hoped to be able to get a lot of radio time during the trip, but various obstacles, including a major solar storm, intervened to disrupt my plans. I did take one opportunity to put my mighty QMX QRP rig on the air, along with my full-wavelength, low apex, VP2E antenna built for 20m. Conditions were starting to deteriorate but I put a few CW QSOs in the log before shutting down the hilltop field station.

The QTH for the radio activity was a small park overlooking Haliburton Village. We had the park all to ourselves for most of our visit, which was a blessing since the VP2E occupies quite a large footprint. The propagation forecast did not look good because of an incoming Coronal Mass Ejection. A planned POTA activation the next day had to be canceled because the CME arrived and made QRP operation a little too challenging.

A learning opportunity

Even though poor propagation conditions limited actual time on the air, the activity did result in a couple of ideas for future radio road trips. First, I noticed I was getting better signal reports from stations thousands of kilometers away – generally to the west and south-west. Contacts along the upper eastern US seaboard were generally more difficult. This result suggests my signal may have had a lower take-off angle than modeling predicts. I have come up with a potential solution for this, thanks to the excellent website at portable-antennas.com. Details later in this post.

My wife and I stayed at a lakeside resort style hotel with more rules and restrictions than you could shake a stick at. Although ham radio was not mentioned specifically, I made the decision not to try to set up a 60ft long wire antenna in the limited space available between our room and the shore of picturesque Kashagawigamog Lake. Lesson learned: take an alternative compact antenna on the next road trip. That idea has stimulated a quest to find options for a low impact, discreet antenna that could be used in situations like this. Reader suggestions are welcome.

Who’s afraid of the big black wolf?

The bands may have been disappointing but our visit to the Haliburton Wolf Center certainly was not. A pack of five wolves is maintained inside a 7 acre enclosure. The wolves can be viewed through one-way glass to ensure they are not intimidated by the presence of humans. The wolves are not socialized and their environment is maintained as close to nature as possible. They are fed every 5-10 days with already dead animals such as beaver, tossed into their pen from a platform. Larger roadkill carcasses – such as moose – are lowered into the pen by crane.

It was very interesting to be able to view these magnificent animals from a safe location. I have camped in the backcountry of nearby Algonquin Park several times and (thankfully) never come into contact with any of the population of several hundred wolves. Algonquin Park is also home to several thousand black bears and, unfortunately, I did once experience a visit to my tiny lakeside campsite by a very large bear in the middle of the night.

Improvements to the VP2E antenna

My VP2E (Vertically Polarized 2-Element) antenna has given good service in many field operations, but over the years, fiddling with wire lengths to optimize SWR and changing the feed arrangement have resulted in a less than optimal configuration that needed correction. Fortunately the VP2E is very forgiving and despite my sometimes clumsy adjustments it just keeps on working.

Followers of this blog may remember I recently installed an air wound Common Mode Current Choke (CMCC) at the VP2E feedpoint. I used this choke during the Haliburton road trip. It worked fine business but it is a little too bulky when packing out for field operations. When we returned from the trip I decided to replace it with another new CMCC. This one is 15 bifilar turns on a FT82-43 toroidal core. It is so compact that it mounts directly on the inelegant feedpoint insulator. Kudos for innovation, brickbats for style!

Another advantage of the new compact CMCC: it gives 33dB common mode current attenuation across the whole 20m band.

What other VP2E improvements?

Why is it that antenna designers assume everybody wants to work DX? I know many operators enjoy DXing, collecting countries and communicating with hams in the land of far-far-away. I usually have a different objective. Most of my field operating time is spent participating in activities like POTA and SOTA.

When I take a look at a map of, for example, POTA activators in North America, a clear picture emerges. What do I see? The vast majority of the activity is in the eastern part of the United States, and mostly in the northeast. It is disappointing to see that POTA operators in Canada are a rare breed!

And where is most of the POTA activity to be found? On the 20m band. The distance between my QTH in southern Ontario and North Carolina is about 750 miles (1200 km). If Florida is included (I often make contacts there too) the distance extends to around 1250 miles (2000 km). A side note: I once drove my family from Toronto to St Petersburg in Florida for a vacation. RF might take a few microseconds to complete the journey, but it took a heck of a lot longer to get there by road. I never repeated that drive; that’s what airplanes are for!

Now, if I want to target the US northeast, it is not the smartest plan to use an antenna designed for DX. It might be a better idea to use the 40m band instead, but that’s not usually where the activity is to be found. So 20m it is, and my antenna needs to have a higher take-off angle to avoid sending my signal sailing right over the heads of operators in my target area. But … not too high a take-off angle that my signal enters the NVIS zone. The ionosphere will not cooperate by refracting 20m signals back to the planet’s surface, the way it does for the lower bands. Instead, high angle signals on the higher bands tend to become outer space explorers.

Here is where portable-antennas.com becomes very useful. The site includes a design feature for the VP2E antenna with which we can experiment with the various dimensions of the antenna and determine the effect on its performance.

I selected a very low apex height of just over 3 meters which nicely matches the height of one of my fiberglass support poles.

Looking at the elevation plot we can see the main lobe at a take-off angle of just over 50 degrees. The -3dB points include a useful component below 30 degrees, but part of the signal is poised to boldly go where where no man has gone before (although Spacex may change that before long). I specified a “good” ground type in my model because my home QTH is in between two huge lakes (Georgian Bay and Lake Huron) with plenty of surface water and high dissolved solids levels. As I travel to other areas where sandy soil or exposed bedrock are present, the antenna will inevitably behave differently. Hey, amateur radio is all about experimentation eh?

As the apex of the VP2E is lowered the model shows the antenna’s directionality improves. This could be a very useful feature. How many other simple wire antennas have the directional property of a beam antenna? Well, apart from the Grasswire (discussed several times in this blog) I can think of none.

I usually point my antennas at Texas and expect to cover the whole of CONUS. Now, while evaluating this new configuration of the VP2E, Washington D.C. may be a better target. I hope that last sentence won’t be misinterpreted by the security bots at the NSA!

The VP2E can be rotated very easily by simply picking up the wire ends and swinging them around. Maximum signal is radiated from “the long end” of the antenna (the VP2E is an off-center fed, full wave wire, so “the long end ” refers to the longest wire end away from the feedpoint).

Note: the VP2E with lower apex is an experiment. Experiments never fail; they only provide data for follow-on experiments with revised parameters. My 10ft pole has extensions for 13ft and 16ft that can be deployed if necessary.

What’s next John?

Now that summer is finally here (that brief period between snow storms here in Ontario) I will be spending more time in the great outdoors trying various antennas. That means Ham Radio Outside the Box will be publishing about every two weeks – unless there is something that needs to be urgently communicated to this blog’s burgeoning list of followers. In that vein, a sincere thank you to all the new followers who have signed up in recent weeks. I have some very interesting ideas to share over the coming weeks so please stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A road trip with the VP2E antenna … and wolves

My wife and I recently took a short early summer vacation in the Haliburton Highlands area of Ontario. The area is just south-west of Algonquin Park (Ontario’s first and by far the largest provincial park, most of which is accessible only by canoe with sometimes very long and challenging portages … and with a very large population of black bears and wolves).

I had hoped to be able to get a lot of radio time during the trip, but various obstacles, including a major solar storm, intervened to disrupt my plans. I did take one opportunity to put my mighty QMX QRP rig on the air, along with my full-wavelength, low apex, VP2E antenna built for 20m. Conditions were starting to deteriorate but I put a few CW QSOs in the log before shutting down the hilltop field station.

The QTH for the radio activity was a small park overlooking Haliburton Village. We had the park all to ourselves for most of our visit, which was a blessing since the VP2E occupies quite a large footprint. The propagation forecast did not look good because of an incoming Coronal Mass Ejection. A planned POTA activation the next day had to be canceled because the CME arrived and made QRP operation a little too challenging.

A learning opportunity

Even though poor propagation conditions limited actual time on the air, the activity did result in a couple of ideas for future radio road trips. First, I noticed I was getting better signal reports from stations thousands of kilometers away – generally to the west and south-west. Contacts along the upper eastern US seaboard were generally more difficult. This result suggests my signal may have had a lower take-off angle than modeling predicts. I have come up with a potential solution for this, thanks to the excellent website at portable-antennas.com. Details later in this post.

My wife and I stayed at a lakeside resort style hotel with more rules and restrictions than you could shake a stick at. Although ham radio was not mentioned specifically, I made the decision not to try to set up a 60ft long wire antenna in the limited space available between our room and the shore of picturesque Kashagawigamog Lake. Lesson learned: take an alternative compact antenna on the next road trip. That idea has stimulated a quest to find options for a low impact, discreet antenna that could be used in situations like this. Reader suggestions are welcome.

Who’s afraid of the big black wolf?

The bands may have been disappointing but our visit to the Haliburton Wolf Center certainly was not. A pack of five wolves is maintained inside a 7 acre enclosure. The wolves can be viewed through one-way glass to ensure they are not intimidated by the presence of humans. The wolves are not socialized and their environment is maintained as close to nature as possible. They are fed every 5-10 days with already dead animals such as beaver, tossed into their pen from a platform. Larger roadkill carcasses – such as moose – are lowered into the pen by crane.

It was very interesting to be able to view these magnificent animals from a safe location. I have camped in the backcountry of nearby Algonquin Park several times and (thankfully) never come into contact with any of the population of several hundred wolves. Algonquin Park is also home to several thousand black bears and, unfortunately, I did once experience a visit to my tiny lakeside campsite by a very large bear in the middle of the night.

Improvements to the VP2E antenna

My VP2E (Vertically Polarized 2-Element) antenna has given good service in many field operations, but over the years, fiddling with wire lengths to optimize SWR and changing the feed arrangement have resulted in a less than optimal configuration that needed correction. Fortunately the VP2E is very forgiving and despite my sometimes clumsy adjustments it just keeps on working.

Followers of this blog may remember I recently installed an air wound Common Mode Current Choke (CMCC) at the VP2E feedpoint. I used this choke during the Haliburton road trip. It worked fine business but it is a little too bulky when packing out for field operations. When we returned from the trip I decided to replace it with another new CMCC. This one is 15 bifilar turns on a FT82-43 toroidal core. It is so compact that it mounts directly on the inelegant feedpoint insulator. Kudos for innovation, brickbats for style!

Another advantage of the new compact CMCC: it gives 33dB common mode current attenuation across the whole 20m band.

What other VP2E improvements?

Why is it that antenna designers assume everybody wants to work DX? I know many operators enjoy DXing, collecting countries and communicating with hams in the land of far-far-away. I usually have a different objective. Most of my field operating time is spent participating in activities like POTA and SOTA.

When I take a look at a map of, for example, POTA activators in North America, a clear picture emerges. What do I see? The vast majority of the activity is in the eastern part of the United States, and mostly in the northeast. It is disappointing to see that POTA operators in Canada are a rare breed!

And where is most of the POTA activity to be found? On the 20m band. The distance between my QTH in southern Ontario and North Carolina is about 750 miles (1200 km). If Florida is included (I often make contacts there too) the distance extends to around 1250 miles (2000 km). A side note: I once drove my family from Toronto to St Petersburg in Florida for a vacation. RF might take a few microseconds to complete the journey, but it took a heck of a lot longer to get there by road. I never repeated that drive; that’s what airplanes are for!

Now, if I want to target the US northeast, it is not the smartest plan to use an antenna designed for DX. It might be a better idea to use the 40m band instead, but that’s not usually where the activity is to be found. So 20m it is, and my antenna needs to have a higher take-off angle to avoid sending my signal sailing right over the heads of operators in my target area. But … not too high a take-off angle that my signal enters the NVIS zone. The ionosphere will not cooperate by refracting 20m signals back to the planet’s surface, the way it does for the lower bands. Instead, high angle signals on the higher bands tend to become outer space explorers.

Here is where portable-antennas.com becomes very useful. The site includes a design feature for the VP2E antenna with which we can experiment with the various dimensions of the antenna and determine the effect on its performance.

I selected a very low apex height of just over 3 meters which nicely matches the height of one of my fiberglass support poles.

Looking at the elevation plot we can see the main lobe at a take-off angle of just over 50 degrees. The -3dB points include a useful component below 30 degrees, but part of the signal is poised to boldly go where where no man has gone before (although Spacex may change that before long). I specified a “good” ground type in my model because my home QTH is in between two huge lakes (Georgian Bay and Lake Huron) with plenty of surface water and high dissolved solids levels. As I travel to other areas where sandy soil or exposed bedrock are present, the antenna will inevitably behave differently. Hey, amateur radio is all about experimentation eh?

As the apex of the VP2E is lowered the model shows the antenna’s directionality improves. This could be a very useful feature. How many other simple wire antennas have the directional property of a beam antenna? Well, apart from the Grasswire (discussed several times in this blog) I can think of none.

I usually point my antennas at Texas and expect to cover the whole of CONUS. Now, while evaluating this new configuration of the VP2E, Washington D.C. may be a better target. I hope that last sentence won’t be misinterpreted by the security bots at the NSA!

The VP2E can be rotated very easily by simply picking up the wire ends and swinging them around. Maximum signal is radiated from “the long end” of the antenna (the VP2E is an off-center fed, full wave wire, so “the long end ” refers to the longest wire end away from the feedpoint).

Note: the VP2E with lower apex is an experiment. Experiments never fail; they only provide data for follow-on experiments with revised parameters. My 10ft pole has extensions for 13ft and 16ft that can be deployed if necessary.

What’s next John?

Now that summer is finally here (that brief period between snow storms here in Ontario) I will be spending more time in the great outdoors trying various antennas. That means Ham Radio Outside the Box will be publishing about every two weeks – unless there is something that needs to be urgently communicated to this blog’s burgeoning list of followers. In that vein, a sincere thank you to all the new followers who have signed up in recent weeks. I have some very interesting ideas to share over the coming weeks so please stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A road trip with the VP2E antenna … and wolves

My wife and I recently took a short early summer vacation in the Haliburton Highlands area of Ontario. The area is just south-west of Algonquin Park (Ontario’s first and by far the largest provincial park, most of which is accessible only by canoe with sometimes very long and challenging portages … and with a very large population of black bears and wolves).

I had hoped to be able to get a lot of radio time during the trip, but various obstacles, including a major solar storm, intervened to disrupt my plans. I did take one opportunity to put my mighty QMX QRP rig on the air, along with my full-wavelength, low apex, VP2E antenna built for 20m. Conditions were starting to deteriorate but I put a few CW QSOs in the log before shutting down the hilltop field station.

The QTH for the radio activity was a small park overlooking Haliburton Village. We had the park all to ourselves for most of our visit, which was a blessing since the VP2E occupies quite a large footprint. The propagation forecast did not look good because of an incoming Coronal Mass Ejection. A planned POTA activation the next day had to be canceled because the CME arrived and made QRP operation a little too challenging.

A learning opportunity

Even though poor propagation conditions limited actual time on the air, the activity did result in a couple of ideas for future radio road trips. First, I noticed I was getting better signal reports from stations thousands of kilometers away – generally to the west and south-west. Contacts along the upper eastern US seaboard were generally more difficult. This result suggests my signal may have had a lower take-off angle than modeling predicts. I have come up with a potential solution for this, thanks to the excellent website at portable-antennas.com. Details later in this post.

My wife and I stayed at a lakeside resort style hotel with more rules and restrictions than you could shake a stick at. Although ham radio was not mentioned specifically, I made the decision not to try to set up a 60ft long wire antenna in the limited space available between our room and the shore of picturesque Kashagawigamog Lake. Lesson learned: take an alternative compact antenna on the next road trip. That idea has stimulated a quest to find options for a low impact, discreet antenna that could be used in situations like this. Reader suggestions are welcome.

Who’s afraid of the big black wolf?

The bands may have been disappointing but our visit to the Haliburton Wolf Center certainly was not. A pack of five wolves is maintained inside a 7 acre enclosure. The wolves can be viewed through one-way glass to ensure they are not intimidated by the presence of humans. The wolves are not socialized and their environment is maintained as close to nature as possible. They are fed every 5-10 days with already dead animals such as beaver, tossed into their pen from a platform. Larger roadkill carcasses – such as moose – are lowered into the pen by crane.

It was very interesting to be able to view these magnificent animals from a safe location. I have camped in the backcountry of nearby Algonquin Park several times and (thankfully) never come into contact with any of the population of several hundred wolves. Algonquin Park is also home to several thousand black bears and, unfortunately, I did once experience a visit to my tiny lakeside campsite by a very large bear in the middle of the night.

Improvements to the VP2E antenna

My VP2E (Vertically Polarized 2-Element) antenna has given good service in many field operations, but over the years, fiddling with wire lengths to optimize SWR and changing the feed arrangement have resulted in a less than optimal configuration that needed correction. Fortunately the VP2E is very forgiving and despite my sometimes clumsy adjustments it just keeps on working.

Followers of this blog may remember I recently installed an air wound Common Mode Current Choke (CMCC) at the VP2E feedpoint. I used this choke during the Haliburton road trip. It worked fine business but it is a little too bulky when packing out for field operations. When we returned from the trip I decided to replace it with another new CMCC. This one is 15 bifilar turns on a FT82-43 toroidal core. It is so compact that it mounts directly on the inelegant feedpoint insulator. Kudos for innovation, brickbats for style!

Another advantage of the new compact CMCC: it gives 33dB common mode current attenuation across the whole 20m band.

What other VP2E improvements?

Why is it that antenna designers assume everybody wants to work DX? I know many operators enjoy DXing, collecting countries and communicating with hams in the land of far-far-away. I usually have a different objective. Most of my field operating time is spent participating in activities like POTA and SOTA.

When I take a look at a map of, for example, POTA activators in North America, a clear picture emerges. What do I see? The vast majority of the activity is in the eastern part of the United States, and mostly in the northeast. It is disappointing to see that POTA operators in Canada are a rare breed!

And where is most of the POTA activity to be found? On the 20m band. The distance between my QTH in southern Ontario and North Carolina is about 750 miles (1200 km). If Florida is included (I often make contacts there too) the distance extends to around 1250 miles (2000 km). A side note: I once drove my family from Toronto to St Petersburg in Florida for a vacation. RF might take a few microseconds to complete the journey, but it took a heck of a lot longer to get there by road. I never repeated that drive; that’s what airplanes are for!

Now, if I want to target the US northeast, it is not the smartest plan to use an antenna designed for DX. It might be a better idea to use the 40m band instead, but that’s not usually where the activity is to be found. So 20m it is, and my antenna needs to have a higher take-off angle to avoid sending my signal sailing right over the heads of operators in my target area. But … not too high a take-off angle that my signal enters the NVIS zone. The ionosphere will not cooperate by refracting 20m signals back to the planet’s surface, the way it does for the lower bands. Instead, high angle signals on the higher bands tend to become outer space explorers.

Here is where portable-antennas.com becomes very useful. The site includes a design feature for the VP2E antenna with which we can experiment with the various dimensions of the antenna and determine the effect on its performance.

I selected a very low apex height of just over 3 meters which nicely matches the height of one of my fiberglass support poles.

Looking at the elevation plot we can see the main lobe at a take-off angle of just over 50 degrees. The -3dB points include a useful component below 30 degrees, but part of the signal is poised to boldly go where where no man has gone before (although Spacex may change that before long). I specified a “good” ground type in my model because my home QTH is in between two huge lakes (Georgian Bay and Lake Huron) with plenty of surface water and high dissolved solids levels. As I travel to other areas where sandy soil or exposed bedrock are present, the antenna will inevitably behave differently. Hey, amateur radio is all about experimentation eh?

As the apex of the VP2E is lowered the model shows the antenna’s directionality improves. This could be a very useful feature. How many other simple wire antennas have the directional property of a beam antenna? Well, apart from the Grasswire (discussed several times in this blog) I can think of none.

I usually point my antennas at Texas and expect to cover the whole of CONUS. Now, while evaluating this new configuration of the VP2E, Washington D.C. may be a better target. I hope that last sentence won’t be misinterpreted by the security bots at the NSA!

The VP2E can be rotated very easily by simply picking up the wire ends and swinging them around. Maximum signal is radiated from “the long end” of the antenna (the VP2E is an off-center fed, full wave wire, so “the long end ” refers to the longest wire end away from the feedpoint).

Note: the VP2E with lower apex is an experiment. Experiments never fail; they only provide data for follow-on experiments with revised parameters. My 10ft pole has extensions for 13ft and 16ft that can be deployed if necessary.

What’s next John?

Now that summer is finally here (that brief period between snow storms here in Ontario) I will be spending more time in the great outdoors trying various antennas. That means Ham Radio Outside the Box will be publishing about every two weeks – unless there is something that needs to be urgently communicated to this blog’s burgeoning list of followers. In that vein, a sincere thank you to all the new followers who have signed up in recent weeks. I have some very interesting ideas to share over the coming weeks so please stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A road trip with the VP2E antenna … and wolves

My wife and I recently took a short early summer vacation in the Haliburton Highlands area of Ontario. The area is just south-west of Algonquin Park (Ontario’s first and by far the largest provincial park, most of which is accessible only by canoe with sometimes very long and challenging portages … and with a very large population of black bears and wolves).

I had hoped to be able to get a lot of radio time during the trip, but various obstacles, including a major solar storm, intervened to disrupt my plans. I did take one opportunity to put my mighty QMX QRP rig on the air, along with my full-wavelength, low apex, VP2E antenna built for 20m. Conditions were starting to deteriorate but I put a few CW QSOs in the log before shutting down the hilltop field station.

The QTH for the radio activity was a small park overlooking Haliburton Village. We had the park all to ourselves for most of our visit, which was a blessing since the VP2E occupies quite a large footprint. The propagation forecast did not look good because of an incoming Coronal Mass Ejection. A planned POTA activation the next day had to be canceled because the CME arrived and made QRP operation a little too challenging.

A learning opportunity

Even though poor propagation conditions limited actual time on the air, the activity did result in a couple of ideas for future radio road trips. First, I noticed I was getting better signal reports from stations thousands of kilometers away – generally to the west and south-west. Contacts along the upper eastern US seaboard were generally more difficult. This result suggests my signal may have had a lower take-off angle than modeling predicts. I have come up with a potential solution for this, thanks to the excellent website at portable-antennas.com. Details later in this post.

My wife and I stayed at a lakeside resort style hotel with more rules and restrictions than you could shake a stick at. Although ham radio was not mentioned specifically, I made the decision not to try to set up a 60ft long wire antenna in the limited space available between our room and the shore of picturesque Kashagawigamog Lake. Lesson learned: take an alternative compact antenna on the next road trip. That idea has stimulated a quest to find options for a low impact, discreet antenna that could be used in situations like this. Reader suggestions are welcome.

Who’s afraid of the big black wolf?

The bands may have been disappointing but our visit to the Haliburton Wolf Center certainly was not. A pack of five wolves is maintained inside a 7 acre enclosure. The wolves can be viewed through one-way glass to ensure they are not intimidated by the presence of humans. The wolves are not socialized and their environment is maintained as close to nature as possible. They are fed every 5-10 days with already dead animals such as beaver, tossed into their pen from a platform. Larger roadkill carcasses – such as moose – are lowered into the pen by crane.

It was very interesting to be able to view these magnificent animals from a safe location. I have camped in the backcountry of nearby Algonquin Park several times and (thankfully) never come into contact with any of the population of several hundred wolves. Algonquin Park is also home to several thousand black bears and, unfortunately, I did once experience a visit to my tiny lakeside campsite by a very large bear in the middle of the night.

Improvements to the VP2E antenna

My VP2E (Vertically Polarized 2-Element) antenna has given good service in many field operations, but over the years, fiddling with wire lengths to optimize SWR and changing the feed arrangement have resulted in a less than optimal configuration that needed correction. Fortunately the VP2E is very forgiving and despite my sometimes clumsy adjustments it just keeps on working.

Followers of this blog may remember I recently installed an air wound Common Mode Current Choke (CMCC) at the VP2E feedpoint. I used this choke during the Haliburton road trip. It worked fine business but it is a little too bulky when packing out for field operations. When we returned from the trip I decided to replace it with another new CMCC. This one is 15 bifilar turns on a FT82-43 toroidal core. It is so compact that it mounts directly on the inelegant feedpoint insulator. Kudos for innovation, brickbats for style!

Another advantage of the new compact CMCC: it gives 33dB common mode current attenuation across the whole 20m band.

What other VP2E improvements?

Why is it that antenna designers assume everybody wants to work DX? I know many operators enjoy DXing, collecting countries and communicating with hams in the land of far-far-away. I usually have a different objective. Most of my field operating time is spent participating in activities like POTA and SOTA.

When I take a look at a map of, for example, POTA activators in North America, a clear picture emerges. What do I see? The vast majority of the activity is in the eastern part of the United States, and mostly in the northeast. It is disappointing to see that POTA operators in Canada are a rare breed!

And where is most of the POTA activity to be found? On the 20m band. The distance between my QTH in southern Ontario and North Carolina is about 750 miles (1200 km). If Florida is included (I often make contacts there too) the distance extends to around 1250 miles (2000 km). A side note: I once drove my family from Toronto to St Petersburg in Florida for a vacation. RF might take a few microseconds to complete the journey, but it took a heck of a lot longer to get there by road. I never repeated that drive; that’s what airplanes are for!

Now, if I want to target the US northeast, it is not the smartest plan to use an antenna designed for DX. It might be a better idea to use the 40m band instead, but that’s not usually where the activity is to be found. So 20m it is, and my antenna needs to have a higher take-off angle to avoid sending my signal sailing right over the heads of operators in my target area. But … not too high a take-off angle that my signal enters the NVIS zone. The ionosphere will not cooperate by refracting 20m signals back to the planet’s surface, the way it does for the lower bands. Instead, high angle signals on the higher bands tend to become outer space explorers.

Here is where portable-antennas.com becomes very useful. The site includes a design feature for the VP2E antenna with which we can experiment with the various dimensions of the antenna and determine the effect on its performance.

I selected a very low apex height of just over 3 meters which nicely matches the height of one of my fiberglass support poles.

Looking at the elevation plot we can see the main lobe at a take-off angle of just over 50 degrees. The -3dB points include a useful component below 30 degrees, but part of the signal is poised to boldly go where where no man has gone before (although Spacex may change that before long). I specified a “good” ground type in my model because my home QTH is in between two huge lakes (Georgian Bay and Lake Huron) with plenty of surface water and high dissolved solids levels. As I travel to other areas where sandy soil or exposed bedrock are present, the antenna will inevitably behave differently. Hey, amateur radio is all about experimentation eh?

As the apex of the VP2E is lowered the model shows the antenna’s directionality improves. This could be a very useful feature. How many other simple wire antennas have the directional property of a beam antenna? Well, apart from the Grasswire (discussed several times in this blog) I can think of none.

I usually point my antennas at Texas and expect to cover the whole of CONUS. Now, while evaluating this new configuration of the VP2E, Washington D.C. may be a better target. I hope that last sentence won’t be misinterpreted by the security bots at the NSA!

The VP2E can be rotated very easily by simply picking up the wire ends and swinging them around. Maximum signal is radiated from “the long end” of the antenna (the VP2E is an off-center fed, full wave wire, so “the long end ” refers to the longest wire end away from the feedpoint).

Note: the VP2E with lower apex is an experiment. Experiments never fail; they only provide data for follow-on experiments with revised parameters. My 10ft pole has extensions for 13ft and 16ft that can be deployed if necessary.

What’s next John?

Now that summer is finally here (that brief period between snow storms here in Ontario) I will be spending more time in the great outdoors trying various antennas. That means Ham Radio Outside the Box will be publishing about every two weeks – unless there is something that needs to be urgently communicated to this blog’s burgeoning list of followers. In that vein, a sincere thank you to all the new followers who have signed up in recent weeks. I have some very interesting ideas to share over the coming weeks so please stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

I’ll be camping in West Virginia in EM97 this week. Going to try to work the #MagicBand with this “thrift store” ham stick dipole and a QMX+.

Is #WestVirginia rare in others’ logs? I hadn’t been able to get it in my last 1.5 years as a Technician.

#HolidayStyle #HamRadio #AmateurRadio #6m #6meters #EM97 #antennas #hamstick #MFJ #QRP

Another one for the radio geeks. Sure, the view across the river is beautiful, but there are antennas on the side.
#AmateurRadio #HamRadio #antennas

Another one for the radio geeks. Sure, the view across the river is beautiful, but there are antennas on the side.
#AmateurRadio #HamRadio #antennas

What to do when the bands suck?

Solar cycle #25 has reached its peak and is on the decline again. We may still have a few years of good propagation left but I am planning ahead. During the last solar minimum I adapted by … forgive me … increasing my transmit power. This time around I hope to keep working QRP, but increase my effective radiated power through bigger, more efficient antennas.

The peak of cycle 25 was actually quite a disappointment. The Sun became hyper-active spewing a few too many Coronal Mass Ejections, flares and high energy particles our way. Hopefully, now that the peak has passed, we might even get some less unpredictable propagation before we hit solar minimum.

As solar activity declines the higher bands seem to be open less often, so my personal focus is on 20m, 30m and 40m. Those bands are open throughout the solar cycle – except during solar storms of course. At least once per week I venture onto 80m for a CW rag chew with friends, but that is at the home QTH. When operating out in the woods 20m, 30m and 40m are my goto bands.

On the subject of “out in the woods” (my happy place), our local black bear population has awoken from its winter slumber and has been seen roaming in people places in my local town.

Bears are not usually a problem, they avoid human contact, but in the spring they are hungry and some of them associate people with food. Female bears with cubs can be very protective of their young which makes them potentially dangerous.

Antenna solutions for challenging conditions

One simple rule should be all that is necessary for getting a signal to propagate when the ionosphere is in combat with an angry Sun – or even when the Sun is dormant. Wire in the air = signal in the air. That is when it is probably a good idea to leave those very short, inductively loaded whips at home and start buying reels of wire and poles.

When I look back at what has worked in the past, the picture becomes very clear. Some of my small collection of QRP radios support only 20m, 30m and 40m. The 20m and 30m bands usually favor longer distance contacts, while 40m is better at shorter range. Out of these three bands I use 20m the most and, during the bottom of the solar cycle, 40m is my most used band. I don’t get on 30m very often; it is a WARC band and some operators dislike “contest-like” activity such as POTA on the WARC bands. No sense creating friction.

Best option for 20m?

This may be a bit of generalization, but a half-wave antenna launches more signal in the air than a quarter-wave. All half-wave antennas are not created equal. For example the very popular End-Fed Half-Wave requires a very carefully engineered matching device. Improperly engineered, one-size-fits-all, high ratio transformers often have very low efficiency.

A 5/8 wave vertical antenna may be even better in some circumstances – for example when the base of the antenna and all the radials are raised above ground. But 5/8 of a wavelength is a bit of a tall order – on 20m that’s 41 feet of antenna waving in the wind. Raise it above ground and you may have to attach a flashing red light at the top.

There is an even better solution. How about a 20m wire antenna that is low to the ground, is slightly directional and offers over 3dBi gain? Ham Radio Outside the Box explored this antenna three years ago; it is called the VP2E. Although VP2E sounds like a callsign (and it actually is a valid callsign) it is an abbreviation for Vertically Polarized 2-Element. It requires no tuner – and the VP2E is one full wavelength long.

I had great success with my VP2E before I stopped using it. It fell out of favor because of just one thing. Proponents of the VP2E claim that no baluns, ununs or feedline chokes are required. Perhaps, in theory, if the currents on either side of the feedpoint are balanced that could be true. In practise, even a small imbalance in the currents can lead to feedline radiation. To prevent this I added a current choke at the feedpoint.

Now this is where a problem arose. The feedpoint is not supported, so a choke hanging from the feedpoint pulls the wire down creating significant sag in the wire. The original choke that was used was made from 3 feet (~1m) of RG-316 coax looped three times through four snap-on ferrites; it weighed 126 grams.

The world’s worst 80m Common Mode Current Choke!

When I decided to resurrect the VP2E I wondered whether I could improve the choke to decrease its weight. I chose to get rid of the heavy ferrites and build an air-core coil choke. I found about 9 feet of RG-174 coax in my junque drawer. I also found an old pill container made of plastic so light it almost defies gravity. After winding the entire length of the RG-174 around the super light plastic former I hooked it up to my NanoVNA to measure its effectiveness.

I ran a scan from 3 to 30 MHz and noted the attenuation across the HF bands. On the 10m band the choke is exceptionally effective with a common mode attenuation exceeding 30dB. On the other end of the scale, the common mode attenuation on the 80m band was a lousy 8dB. Well, the VP2E is a monoband antenna built for 20m, so the choke’s performance on 80m is not a concern.

Performance on 20m is marginal, but acceptable, at -20dB. Since the current imbalance is likely to be small 20dB of common mode attenuation should be quite adequate. And, the new choke weighs in at 67 grams, nearly half the weight of the old choke.

It’s stealthy too

Apart from its gain, another benefit of the VP2E is that it only needs a short pole for support. 4.2 meters (13.8ft) is the recommended height. My crappie pole is about 0.2 meters short but modeling the antenna shows very little impact – you work with what you got!

Where to buy a VP2E

This a real hobbyist’s antenna; you can’t buy it, you gotta build it! A 100ft reel of thin wire – I use silicone coated 22ga wire – is all you need. Cut it to the lengths shown in the diagram above. Solder the wires to a piece of coax feedline and you are ready to get on the air. Choke? I think it helps but you can use the antenna without one.

A versatile short, strong, light support pole

The center of my VP2E is supported on a 13ft crappie pole which is very light for carrying into the field. It is very strong too. Well actually, I threw away the very top sections of two crappie poles and a made a strong, light single pole out of the lower sections. It mounts on a fiberglass driveway marker pushed into the ground.

The exact same pole also works for my 40m wire antenna. It’s a low dipole built for NVIS (Near Vertical Incidence Skywave). More details on that in a later post. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

What to do when the bands suck?

Solar cycle #25 has reached its peak and is on the decline again. We may still have a few years of good propagation left but I am planning ahead. During the last solar minimum I adapted by … forgive me … increasing my transmit power. This time around I hope to keep working QRP, but increase my effective radiated power through bigger, more efficient antennas.

The peak of cycle 25 was actually quite a disappointment. The Sun became hyper-active spewing a few too many Coronal Mass Ejections, flares and high energy particles our way. Hopefully, now that the peak has passed, we might even get some less unpredictable propagation before we hit solar minimum.

As solar activity declines the higher bands seem to be open less often, so my personal focus is on 20m, 30m and 40m. Those bands are open throughout the solar cycle – except during solar storms of course. At least once per week I venture onto 80m for a CW rag chew with friends, but that is at the home QTH. When operating out in the woods 20m, 30m and 40m are my goto bands.

On the subject of “out in the woods” (my happy place), our local black bear population has awoken from its winter slumber and has been seen roaming in people places in my local town.

Bears are not usually a problem, they avoid human contact, but in the spring they are hungry and some of them associate people with food. Female bears with cubs can be very protective of their young which makes them potentially dangerous.

Antenna solutions for challenging conditions

One simple rule should be all that is necessary for getting a signal to propagate when the ionosphere is in combat with an angry Sun – or even when the Sun is dormant. Wire in the air = signal in the air. That is when it is probably a good idea to leave those very short, inductively loaded whips at home and start buying reels of wire and poles.

When I look back at what has worked in the past, the picture becomes very clear. Some of my small collection of QRP radios support only 20m, 30m and 40m. The 20m and 30m bands usually favor longer distance contacts, while 40m is better at shorter range. Out of these three bands I use 20m the most and, during the bottom of the solar cycle, 40m is my most used band. I don’t get on 30m very often; it is a WARC band and some operators dislike “contest-like” activity such as POTA on the WARC bands. No sense creating friction.

Best option for 20m?

This may be a bit of generalization, but a half-wave antenna launches more signal in the air than a quarter-wave. All half-wave antennas are not created equal. For example the very popular End-Fed Half-Wave requires a very carefully engineered matching device. Improperly engineered, one-size-fits-all, high ratio transformers often have very low efficiency.

A 5/8 wave vertical antenna may be even better in some circumstances – for example when the base of the antenna and all the radials are raised above ground. But 5/8 of a wavelength is a bit of a tall order – on 20m that’s 41 feet of antenna waving in the wind. Raise it above ground and you may have to attach a flashing red light at the top.

There is an even better solution. How about a 20m wire antenna that is low to the ground, is slightly directional and offers over 3dBi gain? Ham Radio Outside the Box explored this antenna three years ago; it is called the VP2E. Although VP2E sounds like a callsign (and it actually is a valid callsign) it is an abbreviation for Vertically Polarized 2-Element. It requires no tuner – and the VP2E is one full wavelength long.

I had great success with my VP2E before I stopped using it. It fell out of favor because of just one thing. Proponents of the VP2E claim that no baluns, ununs or feedline chokes are required. Perhaps, in theory, if the currents on either side of the feedpoint are balanced that could be true. In practise, even a small imbalance in the currents can lead to feedline radiation. To prevent this I added a current choke at the feedpoint.

Now this is where a problem arose. The feedpoint is not supported, so a choke hanging from the feedpoint pulls the wire down creating significant sag in the wire. The original choke that was used was made from 3 feet (~1m) of RG-316 coax looped three times through four snap-on ferrites; it weighed 126 grams.

The world’s worst 80m Common Mode Current Choke!

When I decided to resurrect the VP2E I wondered whether I could improve the choke to decrease its weight. I chose to get rid of the heavy ferrites and build an air-core coil choke. I found about 9 feet of RG-174 coax in my junque drawer. I also found an old pill container made of plastic so light it almost defies gravity. After winding the entire length of the RG-174 around the super light plastic former I hooked it up to my NanoVNA to measure its effectiveness.

I ran a scan from 3 to 30 MHz and noted the attenuation across the HF bands. On the 10m band the choke is exceptionally effective with a common mode attenuation exceeding 30dB. On the other end of the scale, the common mode attenuation on the 80m band was a lousy 8dB. Well, the VP2E is a monoband antenna built for 20m, so the choke’s performance on 80m is not a concern.

Performance on 20m is marginal, but acceptable, at -20dB. Since the current imbalance is likely to be small 20dB of common mode attenuation should be quite adequate. And, the new choke weighs in at 67 grams, nearly half the weight of the old choke.

It’s stealthy too

Apart from its gain, another benefit of the VP2E is that it only needs a short pole for support. 4.2 meters (13.8ft) is the recommended height. My crappie pole is about 0.2 meters short but modeling the antenna shows very little impact – you work with what you got!

Where to buy a VP2E

This a real hobbyist’s antenna; you can’t buy it, you gotta build it! A 100ft reel of thin wire – I use silicone coated 22ga wire – is all you need. Cut it to the lengths shown in the diagram above. Solder the wires to a piece of coax feedline and you are ready to get on the air. Choke? I think it helps but you can use the antenna without one.

A versatile short, strong, light support pole

The center of my VP2E is supported on a 13ft crappie pole which is very light for carrying into the field. It is very strong too. Well actually, I threw away the very top sections of two crappie poles and a made a strong, light single pole out of the lower sections. It mounts on a fiberglass driveway marker pushed into the ground.

The exact same pole also works for my 40m wire antenna. It’s a low dipole built for NVIS (Near Vertical Incidence Skywave). More details on that in a later post. Stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Que tengáis buenas noches. Saludos desde Barcelona.
#barcelona #sunset #antennas #catalunya #photography

Que tengáis buenas noches. Saludos desde Barcelona.
#barcelona #sunset #antennas #catalunya #photography

Is Your Antenna Missing Channels Like ABC, CBS, FOX, or NBC? Improve Your Free TV Reception Without Paying Full Price

https://fed.brid.gy/r/https://cordcuttersnews.com/is-your-antenna-missing-channels-like-abc-cbs-fox-or-nbc-improve-your-free-tv-reception-without-paying-full-price/

An alternative mini-GTU design by Tim KQ4TQ

As I mentioned in the last post on Ham Radio Outside the Box, I received a surprise package in the mail from Tim KQ4TQ in Georgia. Tim sent me his build of a mini Ground Tuning Unit (GTU) that is simpler in design than the one I built. Tim’s design is a single inductor of 3 microhenries wound on a T82-6 toroid, in series with a 10-355pF polyvaricon. The polyvaricon used in my original Mini-GTU had a maximum capacitance of only 160pF (I extracted it from a charity store AM/FM radio).

Tim’s GTU was quickly deployed out in the Ham Radio Outside the Box antenna test range (my backyard in Owen Sound, Ontario) for a full evaluation. Tim warned that tuning is very sharp and a steady hand is needed to get the best setting. My aging hands are definitely not as steady as they used to be but I found it was actually quite easy to tune.

The original Mini GTU versus the KQ4TQ GTU

The original Mini GTU recently described here on Ham Radio Outside the Box has 4 inductors, each with a shorting switch, in series with a polyvaricon. The purpose of the switches is to enable binary selection of inductance between 0.5 and 15.5 microhenries. By experiment I had discovered that easiest tuning is obtained when the inductance is low (and, of course, higher inductance introduces ohmic loss). So the objective was to binary select an inductance, starting at the lowest value (0.5uH), adjust the capacitance by rotating the polyvaricon knob and measuring the effect on the antenna’s SWR. Then, if an acceptable SWR is not obtained, add more inductance and measure again. In practise it was discovered that a value of 2 or 3 microhenries works for most of the bands tried. By contrast Tim’s GTU, with its single inductance of 3uH simplifies the tuning procedure. Actually, either design works equally well although the original Mini GTU with 4 inductors can also be deployed as an L-match with precision inductance selection.

I reluctantly felt the need to repackage Tim’s GTU in order to implement a couple of design enhancements. When I nervously advised Tim of what I had done he graciously accepted the ideas. Here are the changes:

The original enclosure (see picture earlier in this post) required an external BNC to binding post adapter which looked clumsy. My first mod was to build Tim’s GTU into a small plastic box from the “River in Brazil” company. An LED and sensor circuit was included to give a visual indication of the best setting of the GTU.

I chose a high brightness LED since the device will often be used in bright sunshine. We do actually get bright sunshine during the brief interval between snow storms that we call “summer” here in Ontario. As I write this my home air-conditioning is actually running for the first time – but we will back to heating again in a couple of days.

A quick reminder about the function of a GTU. A GTU is a ground tuner, it’s purpose is to tune a compromise counterpoise to increase its current flow. Increasing the current flow in the counterpoise allows increased current to flow in the radiator portion of the antenna.

Why use a compromise counterpoise? It is sometimes necessary when setting up in a very restricted space location.

Here is where I went “outside the box” in my thinking. It might have been logical to place the current sensor in the ground circuit. But the end objective is to improve current flow in the radiator, so why not just place the current sensor in the radiating element path? In fact, that is what I did. If you look at the internal picture of the repackaged GTU you will see a wire passing through the inductor (red winding), connecting the binding post at the left end (where the radiator wire connects) to the BNC at the right hand end.

Two small circuit boards are visible. The one on the left contains the high brightness LED, recycled from an old defunct SLA battery box. The other small board contains a Germanium diode, RF bypass capacitor and current limit resistor for the LED. The toroid with the red coil turns is an FT82-43; it forms a 10:1 transformer used to sense the level of current flowing in the radiator path which is then displayed by the LED.

So does it work?

This is that rubber hits the road moment. Appropriate since I just had the winter tires taken off my truck. Those tires, dual-range 4-wheel drive and an economical yet powerful V8 engine got me out of more than one deep snow drift last winter. But, anyway, back to the topic in hand, does it work?

Mike W4AEE recently commented: “why are you using a capacitive coupling plate on top of lossy soil? I don’t understand why you would want to put this huge amount of loss in the antenna system. You’re forcing exchange currents between the vertical element ground system to try to flow through a high resistance that’s in series with the circuit. A single counterpoise wire thrown out on the ground would be better than that.”

Mike has a valid point. But, of course, the objective was not to engineer a perfect antenna the Physics Department would endorse. The original design called for a hiking antenna that can be rapidly deployed in a small clearing in the woods. There are many locations I venture into where it simply isn’t possible to lay out an efficient set of radials. A capacitance plate on the ground is indeed a compromise – as was revealed in a recent post here when I rejected the magic carpet ground plane idea as being inefficient. I tried alternative grounds. Here are a couple of them:

First up was a small hand cart I built specifically for ham use. There is a DC path all the way through the aluminum tubing to the steel mesh platform at the bottom. The mesh platform is a capacitive plate for use with a GTU.

At the top you can see the linear-loaded 20m band radiating element made from commercial 450 ohm window line. Did the LED glow when RF was applied? Yes sir and the measured SWR was 1.3:1. That’s good isn’t it? No, I’ll explain in a minute.

Next up was a 22ft long steel wire marker fence along the side of my driveway. The 3ft high fence was built as a guide when snow piles up in the winter. It didn’t work too well the last couple of winters when it disappeared beneath the snow! Just about the same RF result was obtained as with the hand cart.

Heck, I made plenty QRP CW contacts so why wasn’t I happy with the magic carpet or these ideas? The answer is very simple and is contained in the popular saying “SWR makes you stupid”. Yes, the SWR was well under 1.5:1 … BUT … even with a tested resonant linear-loaded radiating element, the overall antenna including the tuned ground circuit, was not resonant. The best impedance I could obtain was 42-j14.8 ohms. A resonant antenna is purely resistive, i.e. there is no reactive component – ideally 50+j0 ohms. Resonance results in the maximum energy transfer between the transceiver and the antenna.

LESSON LEARNED: A Ground Tuning Unit can transform a high impedance ground to a low impedance that is acceptable to a transceiver. But a transceiver cannot discriminate between a low SWR and a purely resistive load. Low SWR does not necessarily imply resonance.

Just a cotton pickin’ New York minute …

Of course an antenna doesn’t have to be resonant to radiate well – it can be adjusted to resonance by means of a “tuner” (technically an impedance matching unit). So, I added a tuner – I used my “Old Barebones” ham-made Z-match, located at the antenna end of my coax cable. That worked. It brought the antenna system into resonance, even with just a few feet of wire thrown on the ground and tuned by a GTU.

Two is too many, one is good

You heard the old saying “two is one, one is none”. Well it doesn’t apply here. Having two boxes dangling from the antenna is ungood. One box is the GTU and the other is a tuner – one too many. My next project will be to combine those two functions into a single small box. Tim KQ4TQ tried to tell me that already; I should have listened.

We’re getting close to ham hiking heaven; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

An alternative mini-GTU design by Tim KQ4TQ

As I mentioned in the last post on Ham Radio Outside the Box, I received a surprise package in the mail from Tim KQ4TQ in Georgia. Tim sent me his build of a mini Ground Tuning Unit (GTU) that is simpler in design than the one I built. Tim’s design is a single inductor of 3 microhenries wound on a T82-6 toroid, in series with a 10-355pF polyvaricon. The polyvaricon used in my original Mini-GTU had a maximum capacitance of only 160pF (I extracted it from a charity store AM/FM radio).

Tim’s GTU was quickly deployed out in the Ham Radio Outside the Box antenna test range (my backyard in Owen Sound, Ontario) for a full evaluation. Tim warned that tuning is very sharp and a steady hand is needed to get the best setting. My aging hands are definitely not as steady as they used to be but I found it was actually quite easy to tune.

The original Mini GTU versus the KQ4TQ GTU

The original Mini GTU recently described here on Ham Radio Outside the Box has 4 inductors, each with a shorting switch, in series with a polyvaricon. The purpose of the switches is to enable binary selection of inductance between 0.5 and 15.5 microhenries. By experiment I had discovered that easiest tuning is obtained when the inductance is low (and, of course, higher inductance introduces ohmic loss). So the objective was to binary select an inductance, starting at the lowest value (0.5uH), adjust the capacitance by rotating the polyvaricon knob and measuring the effect on the antenna’s SWR. Then, if an acceptable SWR is not obtained, add more inductance and measure again. In practise it was discovered that a value of 2 or 3 microhenries works for most of the bands tried. By contrast Tim’s GTU, with its single inductance of 3uH simplifies the tuning procedure. Actually, either design works equally well although the original Mini GTU with 4 inductors can also be deployed as an L-match with precision inductance selection.

I reluctantly felt the need to repackage Tim’s GTU in order to implement a couple of design enhancements. When I nervously advised Tim of what I had done he graciously accepted the ideas. Here are the changes:

The original enclosure (see picture earlier in this post) required an external BNC to binding post adapter which looked clumsy. My first mod was to build Tim’s GTU into a small plastic box from the “River in Brazil” company. An LED and sensor circuit was included to give a visual indication of the best setting of the GTU.

I chose a high brightness LED since the device will often be used in bright sunshine. We do actually get bright sunshine during the brief interval between snow storms that we call “summer” here in Ontario. As I write this my home air-conditioning is actually running for the first time – but we will back to heating again in a couple of days.

A quick reminder about the function of a GTU. A GTU is a ground tuner, it’s purpose is to tune a compromise counterpoise to increase its current flow. Increasing the current flow in the counterpoise allows increased current to flow in the radiator portion of the antenna.

Why use a compromise counterpoise? It is sometimes necessary when setting up in a very restricted space location.

Here is where I went “outside the box” in my thinking. It might have been logical to place the current sensor in the ground circuit. But the end objective is to improve current flow in the radiator, so why not just place the current sensor in the radiating element path? In fact, that is what I did. If you look at the internal picture of the repackaged GTU you will see a wire passing through the inductor (red winding), connecting the binding post at the left end (where the radiator wire connects) to the BNC at the right hand end.

Two small circuit boards are visible. The one on the left contains the high brightness LED, recycled from an old defunct SLA battery box. The other small board contains a Germanium diode, RF bypass capacitor and current limit resistor for the LED. The toroid with the red coil turns is an FT82-43; it forms a 10:1 transformer used to sense the level of current flowing in the radiator path which is then displayed by the LED.

So does it work?

This is that rubber hits the road moment. Appropriate since I just had the winter tires taken off my truck. Those tires, dual-range 4-wheel drive and an economical yet powerful V8 engine got me out of more than one deep snow drift last winter. But, anyway, back to the topic in hand, does it work?

Mike W4AEE recently commented: “why are you using a capacitive coupling plate on top of lossy soil? I don’t understand why you would want to put this huge amount of loss in the antenna system. You’re forcing exchange currents between the vertical element ground system to try to flow through a high resistance that’s in series with the circuit. A single counterpoise wire thrown out on the ground would be better than that.”

Mike has a valid point. But, of course, the objective was not to engineer a perfect antenna the Physics Department would endorse. The original design called for a hiking antenna that can be rapidly deployed in a small clearing in the woods. There are many locations I venture into where it simply isn’t possible to lay out an efficient set of radials. A capacitance plate on the ground is indeed a compromise – as was revealed in a recent post here when I rejected the magic carpet ground plane idea as being inefficient. I tried alternative grounds. Here are a couple of them:

First up was a small hand cart I built specifically for ham use. There is a DC path all the way through the aluminum tubing to the steel mesh platform at the bottom. The mesh platform is a capacitive plate for use with a GTU.

At the top you can see the linear-loaded 20m band radiating element made from commercial 450 ohm window line. Did the LED glow when RF was applied? Yes sir and the measured SWR was 1.3:1. That’s good isn’t it? No, I’ll explain in a minute.

Next up was a 22ft long steel wire marker fence along the side of my driveway. The 3ft high fence was built as a guide when snow piles up in the winter. It didn’t work too well the last couple of winters when it disappeared beneath the snow! Just about the same RF result was obtained as with the hand cart.

Heck, I made plenty QRP CW contacts so why wasn’t I happy with the magic carpet or these ideas? The answer is very simple and is contained in the popular saying “SWR makes you stupid”. Yes, the SWR was well under 1.5:1 … BUT … even with a tested resonant linear-loaded radiating element, the overall antenna including the tuned ground circuit, was not resonant. The best impedance I could obtain was 42-j14.8 ohms. A resonant antenna is purely resistive, i.e. there is no reactive component – ideally 50+j0 ohms. Resonance results in the maximum energy transfer between the transceiver and the antenna.

LESSON LEARNED: A Ground Tuning Unit can transform a high impedance ground to a low impedance that is acceptable to a transceiver. But a transceiver cannot discriminate between a low SWR and a purely resistive load. Low SWR does not necessarily imply resonance.

Just a cotton pickin’ New York minute …

Of course an antenna doesn’t have to be resonant to radiate well – it can be adjusted to resonance by means of a “tuner” (technically an impedance matching unit). So, I added a tuner – I used my “Old Barebones” ham-made Z-match, located at the antenna end of my coax cable. That worked. It brought the antenna system into resonance, even with just a few feet of wire thrown on the ground and tuned by a GTU.

Two is too many, one is good

You heard the old saying “two is one, one is none”. Well it doesn’t apply here. Having two boxes dangling from the antenna is ungood. One box is the GTU and the other is a tuner – one too many. My next project will be to combine those two functions into a single small box. Tim KQ4TQ tried to tell me that already; I should have listened.

We’re getting close to ham hiking heaven; stay tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Ham radio net today someone was talking about lack of space for an antenna, and also a metal patio cover in the way... I was the only one who told them to use the metal patio cover as the antenna, lol. (lots of "buy this" or "buy that"... conventional consumer thinking exists among the more DIY-oriented, techie ham radio world, too.) #hamradio #antennas

Ham radio net today someone was talking about lack of space for an antenna, and also a metal patio cover in the way... I was the only one who told them to use the metal patio cover as the antenna, lol. (lots of "buy this" or "buy that"... conventional consumer thinking exists among the more DIY-oriented, techie ham radio world, too.) #hamradio #antennas

Does anyone have any experience with these cheap, in both price and quality, extendable flag poles as antenna masts? There are 20 and 25 footers for less than $60 USD. I'm in the city, but have 50 feet across the back of my lot. I'm thinking one of these in each corner with an end fed wire strung between them.

This is a kludge and I wouldn't expect it to survive more than a year but it would get me on the air.

Thoughts?
#HamRadio #AmateurRadio #Antennas

Does anyone have any experience with these cheap, in both price and quality, extendable flag poles as antenna masts? There are 20 and 25 footers for less than $60 USD. I'm in the city, but have 50 feet across the back of my lot. I'm thinking one of these in each corner with an end fed wire strung between them.

This is a kludge and I wouldn't expect it to survive more than a year but it would get me on the air.

Thoughts?
#HamRadio #AmateurRadio #Antennas

The magic carpet ground plane is grounded, but the GTU keeps flying.

Ham Radio Outside the Box receives quite a lot of email every week from readers with questions, comments and suggestions. One such email came about as a result of an article in the outstanding newsletter from the Surrey Amateur Radio Club called the Communicator. The editor of the Communicator is Canadian Amateur Radio Hall of Fame member John Schouten VE7TI. John approached me some time ago to see if I would be willing to be a regular contributor to the Communicator. I readily accepted and I am indebted to the Communicator for publishing a regular series of posts from this blog to the Communicator’s international readers in over 150 countries.

A recent article in the Communicator triggered an email from Guy VA7GI and that sparked a chain of correspondence beginning with a request for more details of the Ground Tuning Unit featured in recent posts on this blog. Then Guy suggested I conduct a test to compare a GTU combined with a Faraday cloth (“Magic Carpet”) capacitance plate on the ground, to a regular set of radials. That sounded like an interesting challenge so I set up a test antenna out in the backyard to find out how the two compared.

An old, bruised and battered, long retired MFJ 20m telescopic whip was mounted on a tripod and promptly caught a gust of wind which sent it crashing to the ground. Fortunately it just missed a large birch tree and landed softly on the grass. More bruises! It was re-erected and secured with cordage to prevent any further falls. Then a 17ft raised wire counterpoise was attached via an RF current sensor.

RF was applied to the antenna by a RigExpert antenna analyzer and a strong deflection was observed on the current sensor. The meter reading was set to mid-scale by adjusting the instrument’s sensitivity control. Now it would be possible to determine whether the current through the GTU/Faraday cloth was higher or lower than the current passing into the wire counterpoise.

Next step; the counterpoise wire was disconnected and the GTU was attached with a wire to the Faraday cloth on the ground. Once again RF was applied and the relative current was observed on the meter. NB: the current sensor does not measure absolute current values; its job is only to compare relative values. I expected the GTU/Faraday cloth ground arrangement to compare favorably with the wire counterpoise, after all I had made multiple contacts with this arrangement. But, to my surprise, the ground current was now lower than the wire counterpoise result.

My “magic carpet”, made of Faraday cloth ordered from the company named after a Brazilian River, was a purchase made for the purpose of experimentation. To its credit, it served its purpose, but I had some reservations about its suitability for field portable radio operations. The first time I laid it out on my backyard lawn was during a day of bright sunshine. I was dazzled by the sunlight reflected from its surface. Those reflections were probably observable from Earth orbit and certainly detracted from the stealth of a field installation. Stealth was restored with a coat of dark green, non-reflective spray paint.

The outdoor environment challenged the installation with another trial – wind. The wind had already laid the antenna whip down, now it blew under and around my one square meter of Faraday cloth making it difficult to secure it to the ground. No spring gusts were going to defeat this scientific experiment, so reinforced grommets were attached to each corner of the cloth which was then tightly and securely held in its place with tent stakes.

After a few deployments the edges of the Faraday cloth began to fray and were secured with Gorilla tape, but the non-reflective paint was beginning to crack where the magic carpet was folded between uses. And then it failed the current test!

The image shows the Ham Radio Outside the Box Linear-Loaded Monopole with Magic Carpet deployed along the shore of Lake Huron during a recent OOTA activation. No, that’s not a typo, OOTA is “Out On The Air”. Check it out online.

So is the Magic Carpet idea dead in the water? Guy VA7GI had another suggestion: “I have two friends with ham rigs on sailboats. They each use a backstay with insulators as a vertical antenna. You’d think with a saltwater ground they have the perfect ground plane. But it’s not that simple. They use folded copper wire in the bilge for a ground. They don’t want to drill a hole in the hull or dangle a wire near the prop. Alternatively, they could use Faraday cloth and your GTU. I bet that’d make a huge difference, especially for trans-ocean sailing.”

So magic carpet rides on the wayward wind are grounded, at least for now. My home QTH is surrounded by the Great Lakes so maybe the the idea of a “floating ground” is worth exploring?

The magic carpet is grounded, but not the GTU!

In a later email Guy VA7GI said: “My intuition is that most verticals have compromised radials, placed wherever convenient or possible. Perhaps all vertical antennas would benefit from a GTU.” On the first point Guy may be right. There is a lot of discussion online about the placement of radials. On the ground, or raised above ground? Positioned to direct an antenna’s radiation in a particular direction? Or spread evenly to enhance the widest ground coupling? And, of course, how many radials?

Guy’s second point: “Perhaps all vertical antennas would benefit from a GTU” got me thinking. Could that idea be of benefit in implementing a limited footprint, vertical quarter-wave field antenna? How does a Ground Tuning Unit work? It resonates a capacitive ground path which increases the current in “the other half” of an antenna. That is an idea worth exploring, so a further test was conducted.

A new, improved linear-loaded monopole was erected. The ham-made ladder line previously used has been replaced with a slightly longer (11.5ft) section of 450 ohm commercial window line. When erected as a quarter-wave vertical worked against a GTU tuned counterpoise, the length is not critical within certain restraints because the electrical length of “the other half” is adjustable by the GTU. A shorter radiating element with a longer counterpoise works, as does a longer radiator with a shorter counterpoise. The antenna impedance changes, but unless taken to extremes, it remains close enough to keep the SWR presented to the transceiver within acceptable limits.

This new test was designed to discover whether a GTU could resonate short raised radials sufficiently well to make the antenna an efficient radiator. This arrangement would get a passing grade if the current through the GTU/short radials combination matched the current passing through full-length radials. It didn’t work out too well with the Faraday cloth so I was skeptical about the outcome of this test.

My 11.5ft linear-loaded monopole was paired with two raised radials each 16.5ft long but with links at 11ft and 13ft. Once again, the current was monitored with the full-length radials and set to mid-scale on the meter as a benchmark. Then the radial links were opened at the 11ft point and the GTU was adjusted for maximum current. This time there was a different outcome. The current matched the result obtained with the full-length radials. So Guy – you were right!

Further tests will be conducted with even shorter raised radials to determine whether the current can be maintained with a minimum possible ground footprint. The objective is to design a simple pedestrian portable antenna that can be deployed in a limited space environment such as small clearings in the woods.

The man from the future

Another project remains on the slate and that is the idea of using a helically wound radiating element as suggested by a reader in New Zealand (the “man from the future” – New Zealand is 16 hours ahead of the Eastern Time Zone). Ham Radio Outside the Box will cover that in a later post.

Meanwhile a package arrived in the mail

I was very pleased to receive a package in the mail from Tim KQ4TQ. Tim sent me a GTU he had built himself and asked me to evaluate it. Tim’s GTU is a slightly different build to my own and I will certainly evaluate it fully and report back here soon. Thanks Tim!

Thanks to all Ham Radio Outside the Box subscribers

I put a lot of work into preparing posts for this blog, but it is a labor of love. I seek no financial return, nor will I accept any; this is a hobby not a business. My motivation is to stimulate discussion and learn from experiments and the feedback of other hams. So it was gratifying when WordPress informed me recently that Ham Radio Outside the Box has now surpassed the modest level of 1000 subscribers. Knowing there is a steadily growing interest in the content generated here makes all the work worthwhile. Thank you!

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

The magic carpet ground plane is grounded, but the GTU keeps flying.

Ham Radio Outside the Box receives quite a lot of email every week from readers with questions, comments and suggestions. One such email came about as a result of an article in the outstanding newsletter from the Surrey Amateur Radio Club called the Communicator. The editor of the Communicator is Canadian Amateur Radio Hall of Fame member John Schouten VE7TI. John approached me some time ago to see if I would be willing to be a regular contributor to the Communicator. I readily accepted and I am indebted to the Communicator for publishing a regular series of posts from this blog to the Communicator’s international readers in over 150 countries.

A recent article in the Communicator triggered an email from Guy VA7GI and that sparked a chain of correspondence beginning with a request for more details of the Ground Tuning Unit featured in recent posts on this blog. Then Guy suggested I conduct a test to compare a GTU combined with a Faraday cloth (“Magic Carpet”) capacitance plate on the ground, to a regular set of radials. That sounded like an interesting challenge so I set up a test antenna out in the backyard to find out how the two compared.

An old, bruised and battered, long retired MFJ 20m telescopic whip was mounted on a tripod and promptly caught a gust of wind which sent it crashing to the ground. Fortunately it just missed a large birch tree and landed softly on the grass. More bruises! It was re-erected and secured with cordage to prevent any further falls. Then a 17ft raised wire counterpoise was attached via an RF current sensor.

RF was applied to the antenna by a RigExpert antenna analyzer and a strong deflection was observed on the current sensor. The meter reading was set to mid-scale by adjusting the instrument’s sensitivity control. Now it would be possible to determine whether the current through the GTU/Faraday cloth was higher or lower than the current passing into the wire counterpoise.

Next step; the counterpoise wire was disconnected and the GTU was attached with a wire to the Faraday cloth on the ground. Once again RF was applied and the relative current was observed on the meter. NB: the current sensor does not measure absolute current values; its job is only to compare relative values. I expected the GTU/Faraday cloth ground arrangement to compare favorably with the wire counterpoise, after all I had made multiple contacts with this arrangement. But, to my surprise, the ground current was now lower than the wire counterpoise result.

My “magic carpet”, made of Faraday cloth ordered from the company named after a Brazilian River, was a purchase made for the purpose of experimentation. To its credit, it served its purpose, but I had some reservations about its suitability for field portable radio operations. The first time I laid it out on my backyard lawn was during a day of bright sunshine. I was dazzled by the sunlight reflected from its surface. Those reflections were probably observable from Earth orbit and certainly detracted from the stealth of a field installation. Stealth was restored with a coat of dark green, non-reflective spray paint.

The outdoor environment challenged the installation with another trial – wind. The wind had already laid the antenna whip down, now it blew under and around my one square meter of Faraday cloth making it difficult to secure it to the ground. No spring gusts were going to defeat this scientific experiment, so reinforced grommets were attached to each corner of the cloth which was then tightly and securely held in its place with tent stakes.

After a few deployments the edges of the Faraday cloth began to fray and were secured with Gorilla tape, but the non-reflective paint was beginning to crack where the magic carpet was folded between uses. And then it failed the current test!

The image shows the Ham Radio Outside the Box Linear-Loaded Monopole with Magic Carpet deployed along the shore of Lake Huron during a recent OOTA activation. No, that’s not a typo, OOTA is “Out On The Air”. Check it out online.

So is the Magic Carpet idea dead in the water? Guy VA7GI had another suggestion: “I have two friends with ham rigs on sailboats. They each use a backstay with insulators as a vertical antenna. You’d think with a saltwater ground they have the perfect ground plane. But it’s not that simple. They use folded copper wire in the bilge for a ground. They don’t want to drill a hole in the hull or dangle a wire near the prop. Alternatively, they could use Faraday cloth and your GTU. I bet that’d make a huge difference, especially for trans-ocean sailing.”

So magic carpet rides on the wayward wind are grounded, at least for now. My home QTH is surrounded by the Great Lakes so maybe the the idea of a “floating ground” is worth exploring?

The magic carpet is grounded, but not the GTU!

In a later email Guy VA7GI said: “My intuition is that most verticals have compromised radials, placed wherever convenient or possible. Perhaps all vertical antennas would benefit from a GTU.” On the first point Guy may be right. There is a lot of discussion online about the placement of radials. On the ground, or raised above ground? Positioned to direct an antenna’s radiation in a particular direction? Or spread evenly to enhance the widest ground coupling? And, of course, how many radials?

Guy’s second point: “Perhaps all vertical antennas would benefit from a GTU” got me thinking. Could that idea be of benefit in implementing a limited footprint, vertical quarter-wave field antenna? How does a Ground Tuning Unit work? It resonates a capacitive ground path which increases the current in “the other half” of an antenna. That is an idea worth exploring, so a further test was conducted.

A new, improved linear-loaded monopole was erected. The ham-made ladder line previously used has been replaced with a slightly longer (11.5ft) section of 450 ohm commercial window line. When erected as a quarter-wave vertical worked against a GTU tuned counterpoise, the length is not critical within certain restraints because the electrical length of “the other half” is adjustable by the GTU. A shorter radiating element with a longer counterpoise works, as does a longer radiator with a shorter counterpoise. The antenna impedance changes, but unless taken to extremes, it remains close enough to keep the SWR presented to the transceiver within acceptable limits.

This new test was designed to discover whether a GTU could resonate short raised radials sufficiently well to make the antenna an efficient radiator. This arrangement would get a passing grade if the current through the GTU/short radials combination matched the current passing through full-length radials. It didn’t work out too well with the Faraday cloth so I was skeptical about the outcome of this test.

My 11.5ft linear-loaded monopole was paired with two raised radials each 16.5ft long but with links at 11ft and 13ft. Once again, the current was monitored with the full-length radials and set to mid-scale on the meter as a benchmark. Then the radial links were opened at the 11ft point and the GTU was adjusted for maximum current. This time there was a different outcome. The current matched the result obtained with the full-length radials. So Guy – you were right!

Further tests will be conducted with even shorter raised radials to determine whether the current can be maintained with a minimum possible ground footprint. The objective is to design a simple pedestrian portable antenna that can be deployed in a limited space environment such as small clearings in the woods.

The man from the future

Another project remains on the slate and that is the idea of using a helically wound radiating element as suggested by a reader in New Zealand (the “man from the future” – New Zealand is 16 hours ahead of the Eastern Time Zone). Ham Radio Outside the Box will cover that in a later post.

Meanwhile a package arrived in the mail

I was very pleased to receive a package in the mail from Tim KQ4TQ. Tim sent me a GTU he had built himself and asked me to evaluate it. Tim’s GTU is a slightly different build to my own and I will certainly evaluate it fully and report back here soon. Thanks Tim!

Thanks to all Ham Radio Outside the Box subscribers

I put a lot of work into preparing posts for this blog, but it is a labor of love. I seek no financial return, nor will I accept any; this is a hobby not a business. My motivation is to stimulate discussion and learn from experiments and the feedback of other hams. So it was gratifying when WordPress informed me recently that Ham Radio Outside the Box has now surpassed the modest level of 1000 subscribers. Knowing there is a steadily growing interest in the content generated here makes all the work worthwhile. Thank you!

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Mini Ground Tuning Unit and a magic carpet for portable ops

In the last couple of posts I discussed my quest for a simple portable antenna that could be rapidly deployed in a very limited space, for example in a small clearing while hiking through the woods. Such an antenna would have to be a short, yet efficient, vertical that occupies a very small footprint on the ground.

The first successful candidate is a Linear-Loaded Monopole which meets all the design criteria and has performed surprisingly well in initial field tests. Ham Radio Outside the Box has received another suggestion from a reader who lives in the future (I’ll explain in an upcoming post) for a helical antenna. We’ll be hitting the outback (out in the backyard) to experiment with that idea very shortly.

Meanwhile, another design criterion is that a hiking antenna should occupy a very small footprint on the ground. My local woodlands sit atop the Niagara Escarpment and are often very rocky – sometimes with wide and dangerous cracks in the bedrock. There is often nowhere to set up ground radials and limited options for raised radials, so an alternative arrangement for “the other half” of a vertical quarter-wave antenna is necessary.

The solution that has been discussed here on Ham Radio Outside the Box is to use a Ground Tuning Unit (GTU) coupled to a small capacitive plate on the ground. There is some spooky physics associated with how a GTU works which we’ll discuss later in this post. But don’t let that discourage you; the science of physics is full of mind-mending spooky stuff.

Introducing the Mini GTU

I built a GTU some years ago which has seen a lot of use. Unfortunately it is rather big for carrying on a hike through the woods. I needed a small, lightweight version for this new use case. The Mini GTU is a simple device as can be seen from the wiring diagram here:

The device comprises four inductances – 4, 2, 1 and 0.5 microhenries. Each inductor has a SPST switch that can be used to short circuit it and thereby bypass it from the inductance selection. This arrangement allows binary selection of inductance from 0.5 to 7.5 microhenries in 0.5 microhenry increments. For this application it was considered unnecessary to increase the inductance any further, but more inductance could be added by doubling the value of each added inductor.

The Mini GTU is connected to the shield side of the coax that connects the antenna to the radio. This is exactly where you would normally connect radials. The other end of the Mini GTU connects to a capacitive plate laid directly on the ground.

What? No ground current meter?

A GTU usually has a ground current meter in series with the current path. That is achieved by adding a sampling circuit – a small toroidal core inductor with a single secondary turn, a diode rectifier and meter. Again, unnecessary in this application because as the current through the GTU increases, so does the current in the radiating part of the antenna. This is indicated by observing the SWR indicator on the radio.

Construction of the Mini GTU

I built the device on a small piece of perfboard. The following two pictures show the layout of the components. As usual, my collection of T37-2 and T37-6 powdered iron cores were deployed. The smallest inductor (0.5uH) was wound on two stacked T37-6 cores. The 1uH and 2uH inductors were each wound on two stacked T37-2 cores. For the 4uH inductor I redeployed the six T37-2 binocular style cores I had used on the 2T2C inductor discussed in a recent post.

Why not just use one tapped inductor and a rotary switch?

That’s a good question. I could have wound a single 7.5 uH inductor with taps every 0.5 microhenries and used a rotary switch to select the appropriate inductance. But that would require good precision in locating the tap points since 0.5uH is a very small inductance that is more easily wound on a small core.

It is unnecessary to wind these smaller inductors to the precise values specified. Even using tiny T37 cores, a single turn can change the inductance quite a bit. I strove for a precision of about 10% which turned out to be very achievable.

About that capacitive plate on the ground …

Various different types of plate were tried. Pizza trays, hardware cloth and chicken wire all sorta worked. I wasn’t happy with any of them though. They are not very easily carried on a hike and one, the hardware cloth, had sharp cut steel wire edges that attacked me viciously when I handled it. A better solution had to be found.

Why don’t you come with me … on a magic carpet ride

I bought a piece of Faraday cloth to try out. This material is very light and easy to pack away in a backpack while hiking. Faraday cloth is sometimes referred to as “magic carpet” in ham radio circles and perhaps with good reason. It is made of several layers with interwoven dense conducting material. I purchased a piece of magic carpet from the “Brazilian River” company. It measures 39×43 inches (very nearly 1 square meter).

One square meter is a little larger than I had hoped for in this application so I folded it twice to created a nearly square smaller footprint. If that worked the plan was to cut the sheet into four pieces and use just a single piece for my hiking antenna. Did it work? With the smallest footprint and adjustment of the Mini GTU for best SWR indication on the radio an SWR of 1.68:1 was obtained. Not bad, in fact very usable, but could a bigger magic carpet go even better?

Second test: the magic carpet was folded in half. Now it was a rectangle and with the Mini GTU adjusted the best SWR dropped to 1.45:1. Obviously a trend had been established. Could the whole sheet of magic carpet top the trend?

Third test: now the whole square meter of Faraday cloth lay spread on the ground, secured from the wind with some rocks surreptitiously borrowed from my wife’s garden bed (thanks to all the ancient Norse gods she doesn’t read my blog). The SWR dropped again to 1.13:1. Jingolaba!

Conclusion: “magic carpet” seems to be best solution. If the available trail-side operating site is too small for the whole one square meter of cloth, it can be folded once or even twice while keeping the SWR well below 2:1.

Other hams have tried even larger sheets of Faraday cloth for a ground plane and achieved good results, but without a GTU. The advantage of the GTU is that only a very small capacitive ground plate is required to achieve the same or better results.

One more final note: antenna physicists will note I have been using SWR as a measurement of the effectiveness of the hiking antenna. Of course, lowest SWR does not imply resonance, but radios do not have any way of measuring and displaying complex impedance values and an antenna analyzer would add to the weight needed to be carried into the field when hiking.

Addendum: a bit of spooky physics to (explain?) how a GTU works

A quarter-wave vertical antenna radiates sinusoidal voltage and current waves into an imaginary medium called the “ether”. At the same time a mirror image of these waves is generated in the ground. These mirror image waves are as real as the “ether”. If we were to bury a current meter in the ground beneath the antenna would it record the mirror image? Unrenowned scientists like myself (I earned a bachelor’s degree in physics way back when) say no.

There are three reasons why not. First, and most obvious, we cannot read a meter buried in the ground. Second, no because the mirror image is virtual not real. And the third reason is really spooky. If you search on the Whirled Wild Web for the “double slit” experiment you will learn that spooky physics stuff only happens when scientists don’t try to monitor it. That experiment is one of the most mind-bending, unexplained phenomena that even amateur scientists can attempt to reproduce. So what happens to the real current flowing through the GTU? RF gotta go somewhere.

The concept of virtual images can be seen in this picture of looking at a transceiver in a mirror. If we trace the path of the light rays through the mirror we can see a mirror image of the transceiver at the same distance behind the mirror as the actual transceiver is in front of the mirror. Step behind the mirror and you won’t find the virtual mirror image. A fanciful thought emerges here. Maybe science will one day find a way to create that expensive radio you can’t afford using a virtual image held behind a mirror.

Physics can take spookiness to extremes. My own favorite is a topic called quantum entanglement. If really mind-bending science interests you, try typing that into your search engine. Even one of the greatest scientific minds of all time, Albert Einstein, called that “spooky action at a distance”.

Back to the future

My next project will be developing this week. I replied to the reader “from the future” and will be exploring his ideas in my backyard where intermittent snow cover is heralding the very slow birth of another spring season. Stayed tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

A Mini Ground Tuning Unit and a magic carpet for portable ops

In the last couple of posts I discussed my quest for a simple portable antenna that could be rapidly deployed in a very limited space, for example in a small clearing while hiking through the woods. Such an antenna would have to be a short, yet efficient, vertical that occupies a very small footprint on the ground.

The first successful candidate is a Linear-Loaded Monopole which meets all the design criteria and has performed surprisingly well in initial field tests. Ham Radio Outside the Box has received another suggestion from a reader who lives in the future (I’ll explain in an upcoming post) for a helical antenna. We’ll be hitting the outback (out in the backyard) to experiment with that idea very shortly.

Meanwhile, another design criterion is that a hiking antenna should occupy a very small footprint on the ground. My local woodlands sit atop the Niagara Escarpment and are often very rocky – sometimes with wide and dangerous cracks in the bedrock. There is often nowhere to set up ground radials and limited options for raised radials, so an alternative arrangement for “the other half” of a vertical quarter-wave antenna is necessary.

The solution that has been discussed here on Ham Radio Outside the Box is to use a Ground Tuning Unit (GTU) coupled to a small capacitive plate on the ground. There is some spooky physics associated with how a GTU works which we’ll discuss later in this post. But don’t let that discourage you; the science of physics is full of mind-mending spooky stuff.

Introducing the Mini GTU

I built a GTU some years ago which has seen a lot of use. Unfortunately it is rather big for carrying on a hike through the woods. I needed a small, lightweight version for this new use case. The Mini GTU is a simple device as can be seen from the wiring diagram here:

The device comprises four inductances – 4, 2, 1 and 0.5 microhenries. Each inductor has a SPST switch that can be used to short circuit it and thereby bypass it from the inductance selection. This arrangement allows binary selection of inductance from 0.5 to 7.5 microhenries in 0.5 microhenry increments. For this application it was considered unnecessary to increase the inductance any further, but more inductance could be added by doubling the value of each added inductor.

The Mini GTU is connected to the shield side of the coax that connects the antenna to the radio. This is exactly where you would normally connect radials. The other end of the Mini GTU connects to a capacitive plate laid directly on the ground.

What? No ground current meter?

A GTU usually has a ground current meter in series with the current path. That is achieved by adding a sampling circuit – a small toroidal core inductor with a single secondary turn, a diode rectifier and meter. Again, unnecessary in this application because as the current through the GTU increases, so does the current in the radiating part of the antenna. This is indicated by observing the SWR indicator on the radio.

Construction of the Mini GTU

I built the device on a small piece of perfboard. The following two pictures show the layout of the components. As usual, my collection of T37-2 and T37-6 powdered iron cores were deployed. The smallest inductor (0.5uH) was wound on two stacked T37-6 cores. The 1uH and 2uH inductors were each wound on two stacked T37-2 cores. For the 4uH inductor I redeployed the six T37-2 binocular style cores I had used on the 2T2C inductor discussed in a recent post.

Why not just use one tapped inductor and a rotary switch?

That’s a good question. I could have wound a single 7.5 uH inductor with taps every 0.5 microhenries and used a rotary switch to select the appropriate inductance. But that would require good precision in locating the tap points since 0.5uH is a very small inductance that is more easily wound on a small core.

It is unnecessary to wind these smaller inductors to the precise values specified. Even using tiny T37 cores, a single turn can change the inductance quite a bit. I strove for a precision of about 10% which turned out to be very achievable.

About that capacitive plate on the ground …

Various different types of plate were tried. Pizza trays, hardware cloth and chicken wire all sorta worked. I wasn’t happy with any of them though. They are not very easily carried on a hike and one, the hardware cloth, had sharp cut steel wire edges that attacked me viciously when I handled it. A better solution had to be found.

Why don’t you come with me … on a magic carpet ride

I bought a piece of Faraday cloth to try out. This material is very light and easy to pack away in a backpack while hiking. Faraday cloth is sometimes referred to as “magic carpet” in ham radio circles and perhaps with good reason. It is made of several layers with interwoven dense conducting material. I purchased a piece of magic carpet from the “Brazilian River” company. It measures 39×43 inches (very nearly 1 square meter).

One square meter is a little larger than I had hoped for in this application so I folded it twice to created a nearly square smaller footprint. If that worked the plan was to cut the sheet into four pieces and use just a single piece for my hiking antenna. Did it work? With the smallest footprint and adjustment of the Mini GTU for best SWR indication on the radio an SWR of 1.68:1 was obtained. Not bad, in fact very usable, but could a bigger magic carpet go even better?

Second test: the magic carpet was folded in half. Now it was a rectangle and with the Mini GTU adjusted the best SWR dropped to 1.45:1. Obviously a trend had been established. Could the whole sheet of magic carpet top the trend?

Third test: now the whole square meter of Faraday cloth lay spread on the ground, secured from the wind with some rocks surreptitiously borrowed from my wife’s garden bed (thanks to all the ancient Norse gods she doesn’t read my blog). The SWR dropped again to 1.13:1. Jingolaba!

Conclusion: “magic carpet” seems to be best solution. If the available trail-side operating site is too small for the whole one square meter of cloth, it can be folded once or even twice while keeping the SWR well below 2:1.

Other hams have tried even larger sheets of Faraday cloth for a ground plane and achieved good results, but without a GTU. The advantage of the GTU is that only a very small capacitive ground plate is required to achieve the same or better results.

One more final note: antenna physicists will note I have been using SWR as a measurement of the effectiveness of the hiking antenna. Of course, lowest SWR does not imply resonance, but radios do not have any way of measuring and displaying complex impedance values and an antenna analyzer would add to the weight needed to be carried into the field when hiking.

Addendum: a bit of spooky physics to (explain?) how a GTU works

A quarter-wave vertical antenna radiates sinusoidal voltage and current waves into an imaginary medium called the “ether”. At the same time a mirror image of these waves is generated in the ground. These mirror image waves are as real as the “ether”. If we were to bury a current meter in the ground beneath the antenna would it record the mirror image? Unrenowned scientists like myself (I earned a bachelor’s degree in physics way back when) say no.

There are three reasons why not. First, and most obvious, we cannot read a meter buried in the ground. Second, no because the mirror image is virtual not real. And the third reason is really spooky. If you search on the Whirled Wild Web for the “double slit” experiment you will learn that spooky physics stuff only happens when scientists don’t try to monitor it. That experiment is one of the most mind-bending, unexplained phenomena that even amateur scientists can attempt to reproduce. So what happens to the real current flowing through the GTU? RF gotta go somewhere.

The concept of virtual images can be seen in this picture of looking at a transceiver in a mirror. If we trace the path of the light rays through the mirror we can see a mirror image of the transceiver at the same distance behind the mirror as the actual transceiver is in front of the mirror. Step behind the mirror and you won’t find the virtual mirror image. A fanciful thought emerges here. Maybe science will one day find a way to create that expensive radio you can’t afford using a virtual image held behind a mirror.

Physics can take spookiness to extremes. My own favorite is a topic called quantum entanglement. If really mind-bending science interests you, try typing that into your search engine. Even one of the greatest scientific minds of all time, Albert Einstein, called that “spooky action at a distance”.

Back to the future

My next project will be developing this week. I replied to the reader “from the future” and will be exploring his ideas in my backyard where intermittent snow cover is heralding the very slow birth of another spring season. Stayed tuned.

Help support HamRadioOutsidetheBox

No “tip-jar”, “buy me a coffee”, Patreon, or Amazon links here. I enjoy my hobby and I enjoy writing about it. If you would like to support this blog please follow/subscribe using the link at the bottom of my home page, or like, comment (links at the bottom of each post), repost or share links to my posts on social media. If you would like to email me directly you will find my email address on my QRZ.com page. Thank you!

The following copyright notice applies to all content on this blog.

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.