#ground — Public Fediverse posts
Live and recent posts from across the Fediverse tagged #ground, aggregated by home.social.
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https://www.europesays.com/iran/111739/ Strait of Hormuz: A Testing Ground for Claimants to Global Security #%Increase #a #actions #Alongside #and #are #british #calling #claim #Claimants #contradictions #defensive #encountered #for #French #Global #Ground #has #Hormuz #in #into #Islam #LEGAL #Military #movements #nature #objectives #of #political #question #security #serious #strait #StraitOfHormuz #Testing #that #the #These #Times #to #true #West
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Marina considers Asian American garden for Locke-Paddon Park amid cleanup concerns https://www.allforgardening.com/1754596/marina-considers-asian-american-garden-for-locke-paddon-park-amid-cleanup-concerns/ #agreement #AsianAmericanGarden #city #CleanupConcern #Council #delgado #Future #garden #Ground #LockePaddonPark #marina #MoreAttention #ParkDistrict #Resident #UsefulLand #WetlandHabitat
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"the powers keep.on lyin'
while the people keep on dyin'
the world keeps on turnin'but, it won't be too long"
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終焉の刃 Кінець Леза
嘆きの声は届かない
Цей біль не зцілить.https://www.pixiv.net/novel/show.php?id=27948852
<>
#ＡＩ生成 #roar #echoes #within #darkness #night #sky #battlefield #every #fade #away #cries #sorrow #never #reach #Family #vanished #burned #ground #dare #say #come #word #but #alone #enough #ceasefire #those #longer #change
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終焉の刃 Кінець Леза
嘆きの声は届かない
Цей біль не зцілить.https://note.com/poison_raika/n/ndad834d86db3
<>
#ＡＩ生成 #roar #echoes #within #darkness #night #sky #battlefield #every #fade #away #cries #sorrow #never #reach #Family #vanished #burned #ground #dare #say #come #word #but #alone #enough #ceasefire #those #longer #change
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India bans ashwagandha leaf use in any form, industry reacts
Announcing the ban, the country’s Food Safety and Standards Authority (FSSAI) referred to schedul…
#NewsBeep #News #Medication #asgandh #asian #bottom #Branch #CA #Canada #chop #closeup #concept #fresh #green #Ground #growing #Health #Healthcare #herbal #isolated #knife #lateral #leaves #Natural #outdoor #part #piece #remedy #slice #smell #SOIL #solanaceae #spring #Tools #wellness #withaniasomnifera
https://www.newsbeep.com/ca/635364/ -
India bans ashwagandha leaf use in any form, industry reacts
Announcing the ban, the country’s Food Safety and Standards Authority (FSSAI) referred to …
#NewsBeep #News #Medication #asgandh #asian #bottom #branch #chop #closeup #concept #fresh #Green #ground #growing #Health #healthcare #herbal #isolated #knife #lateral #leaves #Natural #outdoor #part #piece #Remedy #slice #Smell #SOIL #solanaceae #spring #tools #UK #UnitedKingdom #wellness #withaniasomnifera
https://www.newsbeep.com/uk/556000/ -
https://www.europesays.com/ie/458749/ India bans ashwagandha leaf use in any form, industry reacts #asgandh #asian #bottom #Branch #chop #closeup #concept #Éire #fresh #green #ground #growing #Health #Healthcare #herbal #IE #Ireland #isolated #knife #lateral #leaves #Medication #natural #outdoor #part #piece #remedy #slice #smell #soil #solanaceae #spring #tools #wellness #WithaniaSomnifera
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https://www.europesays.com/uk/925176/ India bans ashwagandha leaf use in any form, industry reacts #asgandh #Asian #bottom #Branch #chop #closeup #concept #fresh #Green #ground #growing #Health #Healthcare #herbal #isolated #knife #lateral #leaves #Medication #Natural #outdoor #part #piece’ #remedy #slice #smell #soil #solanaceae #spring #tools #UK #UnitedKingdom #Wellness #WithaniaSomnifera
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https://www.fogolf.com/1231428/one-mistake-golfers-make-that-weakens-entire-courses-golf-golfcourse/ One Mistake Golfers Make That Weakens Entire Courses #golf #golfcourse #damage #education #environment #field #Golf #GolfCourse #GolfCourses #grass #Ground #learning #Maintenance #nature #Outdoor #repair #rules #Science #Shorts #sports #Surface #trending #viral #water #youtube
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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.
Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiringAbout 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.
Mirror image – is it real or virtual?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.
#AmateurRadio #Antennas #Ground #OutdoorOps #Portable
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.
Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiringAbout 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.
Mirror image – is it real or virtual?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.
#AmateurRadio #Antennas #Ground #OutdoorOps #Portable
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.
Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiringAbout 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.
Mirror image – is it real or virtual?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.
#AmateurRadio #Antennas #Ground #OutdoorOps #Portable
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.
Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiringAbout 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.
Mirror image – is it real or virtual?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.
#AmateurRadio #Antennas #Ground #OutdoorOps #Portable
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.
Mini GTU top side showing polyvaricon and inductance selector switches Mini GTU bottom side showing inductors and switch wiringAbout 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.
Mirror image – is it real or virtual?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.
#AmateurRadio #Antennas #Ground #OutdoorOps #Portable
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. -
The glorious toil of taking care of a very big meadow https://www.allforgardening.com/1724171/the-glorious-toil-of-taking-care-of-a-very-big-meadow/ #agriculture #background #brown #close #closeup #compost #Concept #conservation #cultivated #detail #dirt #earth #ecology #environment #Environmental #farm #field #fresh #garden #gardening #Ground #growing #growth #grunge #hand #isolated #Land #life #macro #Mud #natural #nature #nobody #organic #pattern #Peat #soil #Surface #texture #up #white
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European Ground Motion Service (#EGMS)
--
https://doi.org/10.1016/j.rse.2026.115389 <-- shared paper
--
#GIS #spatial #mapping #EuropeanGroundMotionService #EGMS #copernicus #satellite #PersistentScattererInterferometry #SAR #sentinel #sentinel1 #displacement #deformation #useruptake #serviceevolution #Envisat #InSAR #ROSEL #CopernicusGlobalGroundMotionService #CGGMS #risk #hazard #disaster #ground #motion #surface #deformation #usecase #subsidence #differential #remotesensing #earthobservation
@ESA -
European Ground Motion Service (#EGMS)
--
https://doi.org/10.1016/j.rse.2026.115389 <-- shared paper
--
#GIS #spatial #mapping #EuropeanGroundMotionService #EGMS #copernicus #satellite #PersistentScattererInterferometry #SAR #sentinel #sentinel1 #displacement #deformation #useruptake #serviceevolution #Envisat #InSAR #ROSEL #CopernicusGlobalGroundMotionService #CGGMS #risk #hazard #disaster #ground #motion #surface #deformation #usecase #subsidence #differential #remotesensing #earthobservation
@ESA -
European Ground Motion Service (#EGMS)
--
https://doi.org/10.1016/j.rse.2026.115389 <-- shared paper
--
#GIS #spatial #mapping #EuropeanGroundMotionService #EGMS #copernicus #satellite #PersistentScattererInterferometry #SAR #sentinel #sentinel1 #displacement #deformation #useruptake #serviceevolution #Envisat #InSAR #ROSEL #CopernicusGlobalGroundMotionService #CGGMS #risk #hazard #disaster #ground #motion #surface #deformation #usecase #subsidence #differential #remotesensing #earthobservation
@ESA -
European Ground Motion Service (#EGMS)
--
https://doi.org/10.1016/j.rse.2026.115389 <-- shared paper
--
#GIS #spatial #mapping #EuropeanGroundMotionService #EGMS #copernicus #satellite #PersistentScattererInterferometry #SAR #sentinel #sentinel1 #displacement #deformation #useruptake #serviceevolution #Envisat #InSAR #ROSEL #CopernicusGlobalGroundMotionService #CGGMS #risk #hazard #disaster #ground #motion #surface #deformation #usecase #subsidence #differential #remotesensing #earthobservation
@ESA -
European Ground Motion Service (#EGMS)
--
https://doi.org/10.1016/j.rse.2026.115389 <-- shared paper
--
#GIS #spatial #mapping #EuropeanGroundMotionService #EGMS #copernicus #satellite #PersistentScattererInterferometry #SAR #sentinel #sentinel1 #displacement #deformation #useruptake #serviceevolution #Envisat #InSAR #ROSEL #CopernicusGlobalGroundMotionService #CGGMS #risk #hazard #disaster #ground #motion #surface #deformation #usecase #subsidence #differential #remotesensing #earthobservation
@ESA -
A Linear-Loaded Monopole antenna for hiking
There is a lot of information online about Linear-Loaded Dipoles, but I haven’t found anything at all about cutting a Linear-Loaded Dipole in half to create a Linear-Loaded Monopole worked against ground. The legendary L.B. Cebik (W4RNL, SK) published a design philosophy for an 80m Linear-Loaded Monopole, but it didn’t match what I had in mind. So I decided to build one for the purpose of experimentation. Maybe I could make it into a compact, lightweight antenna capable of rapid deployment while hiking – maybe.
What is Linear-Loading?
According to my search engine’s “Search Assist”, “Linear loading is a technique used in antenna design where a portion of the antenna wire is folded back on itself to reduce its overall length while maintaining good electrical performance. This method allows for a shorter antenna that can still operate effectively on the desired frequency.”
Sounds very simple doesn’t it? In the real world, where the RF hits the ether, it gets a little more complicated – especially when venturing outside the box. I could have made life nice and simple by building a Linear-Loaded Dipole; there are lots of designs available online that I could have used. But a dipole is too large for agile, rapid deployments; it needs a taller pole which, in turn, requires pegging into the ground and guy wires. I could use a tree limb for support, but only if suitable trees are available; often they are not. No, my requirement for a very simple hiking antenna implies a vertical antenna – a short vertical antenna.
Short antennas are easy to build; simply add a loading coil at the base and Bob’s your uncle. But that won’t qualify for my purposes. Short loaded antennas have a reduced radiation resistance and ohmic loss in the coil – they are inefficient. So how to shorten an antenna while maintaining efficiency? That’s where linear loading comes into play. A linear-loaded antenna is almost as efficient as a regular version.
How to build a Linear-Loaded Monopole?
It should have been “EZ-PZ”. Just take the dimensions from any of the online designs for a Linear-Loaded Dipole and cut them in half. That’s where I started. For a 20 meter antenna, a length of around 11 feet of window line, shorted at one end, is a good starting point. I hauled it up the mast in my newly glacier-free backyard, attached a counterpoise wire and started trimming. Between snips the resonant frequency was monitored on my RigExpert antenna analyzer. I use the term “resonant frequency” loosely in this context. The expected impedance of a quarter-wave vertical is around 37 ohms which implies there will be some reactive component to the impedance. I searched for a dip in SWR over a wide frequency range until it was possible to locate where the antenna was “resonant”.
Home made ladder line. The separators are made of shrink wrap heated with a Weller soldering gun with plastic welding tip. Lots of work and not very elegant, but practical and cheap!So long John?
A low SWR in the region of the bottom end of the 20 meter band was the target, but the dip in the curve was below the bottom of the band – way below. I snipped and snipped until that dip fell where it was needed. Then the counterpoise length was adjusted until the lowest SWR was obtained. How long was my ladder line? A large pile of snipped ladder line lay on the grass beneath the pole. When I took the antenna down, laid it out on the ground and measured its length it was quite a surprise to see the ladder line radiator was only 8.67ft (2.64m) long. And the counterpoise length was 18ft (5.5m).
Jingo-la-ba!
Will it QSO? I fired a smidgen less than five watts into it and received a response from a station somewhere in the US with an encouraging signal report. Well, at least it “works”. But now came the next step. That pesky 18ft counterpoise had to go, to be replaced with the 2T2C (Tuned Tank Circuit Coupler) described in the last post.
A new challenge
The 2T2C ground coupler was directly connected to the ground side of the short coax feedline and a further wire was added to connect to a small capacitance plate on the ground. Life is complicated and then you die, so why do I insist on adding more complications? It’s called experimentation – experiment and learn! I learned. I learned that my choice of inductance and capacitance for the 2T2C resulted in impossibly sharp tuning of the ground circuit. The 2T2C needed a design modification to reduce the inductance and increase the capacitance. Spreadsheet modeling suggested this would make the 2T2C easier to adjust. I needed to confirm that before rebuilding the 2T2C, but how?
L-match innovation
The answer came in the form of a variable L-match that I built quite recently. It has switch selectable inductors and a variable capacitor. It could be adapted to fit this bill very nicely.
This idea was inspired by VK3YE who published a YouTube video about it some time ago. At one terminal of the L-match a connection is made to the BNC center conductor. At the other terminal, a connection is made to the shield side of the BNC. If you trace the signal path through the device it can be seen that the inductors and capacitor are in series. Now we have a Ground Tuning Unit (GTU) and can use binary selection of the inductances, together with rotating the variable capacitor, to determine the combination of inductance and capacitance for easiest tuning of the ground connection.
The inductances available on my L-match are 0.5, 1, 2, 4, 8 microhenries, allowing the inductance to be varied up to 15.5 microhenries in 0.5 microhenry increments. The variable capacitor is a 30-160pF polyvaricon.
Now, with the 8.67ft linear-loaded vertical erected and the “L-match GTU” making the ground connection via a capacitance plate on the ground, it was easy to select values that would allow smooth adjustment of the antenna SWR. It was found that 1 or 1.5 microhenries worked best. With these values selected the polyvaricon could be adjusted around mid-range to easily select best SWR.
A caution!
There’s a gotcha with this technique. My L-match has a switch to connect the top end of the variable capacitor to either the input or output. This is used to enable fast selection of either high or low impedance antennas. Referring to the diagram above, if the switch (not shown) is set to connect the variable capacitor to the left side of the inductors, this technique will not work. The inductors will be out of circuit and only the variable capacitor will be in circuit.
Will it still QSO?
My low-band QMX was dug out of its field pack and hooked up to the revised antenna (8.67ft of vertical window line with the “L-match GTU” providing the “other half” of the antenna. Using the “Tune SWR” feature of the QMX, the best SWR of 1.36:1 was obtained by a very small adjustment of the variable capacitor in the L-match GTU. Then it was time to go hunting. My best contact was in the state of Arizona (the “Arid Zone”?) almost 3000km away from my station in Southern Ontario. Signal reports were 599 each way. My sent report was a genuine 599 suggesting the antenna has good ears. The 599 report I received may have been genuine or perhaps it was just a “contest report”. In any event a good solid contact was made. A second contact into North Carolina only yielded a 549 signal report, but perhaps the low angle radiation pattern favored longer distance contacts.
Notice that the L-match GTU has no RF current meter. I could perhaps have inserted my home brewed RF current meter in circuit, but it wasn’t really necessary. Adjusting the ground current also regulates the radiating element current. Simply adjusting for lowest SWR indication on the radio peaks the radiated energy.
For practical outdoor use while hiking through the woods and rapidly deploying the antenna in clearings, the L-match GTU will be replaced with a much smaller series L-C coupler (2T2C). A 13ft Crappie pole is used to support the antenna. It collapses to the perfect length for carrying inside a fishing pole bag (no surprise there then) and is very lightweight.
There’s another gotcha
When the current distribution on the antenna was viewed in EZNEC it was discovered that the current maximum is in the ground circuit instead of in the radiator. Just like any ground-mounted antenna, this can lead to ground losses and inefficiency. However, the primary design objective was not to seek a Nobel Prize in antenna physics, but to come up with a design that meets the objective of a rapid deployment, simple antenna for hiking through the woods. The Linear-Loaded Monopole may just meet that requirement, but I have other ideas to try first. 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.
#AmateurRadio #Antennas #Counterpoise #Ground #OutdoorOps #Portable #QMX
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. -
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
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just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
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just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
-
just came across this great project #ground in #hull, #england & decided to support them with monthly #MutualAid. i wish there was a place like that in every town & city.
please consider a donation to this badly needed community hub in one of the most deprived areas on the island.https://www.crowdfunder.co.uk/p/qr/8WOkzDaW?
#press #news #CrowdSourcing #donate #DIY #CommunityBuilding #educate -#organise #resist 🖤☮️🏴✊🏻
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Iran calls on public to find ‘enemy pilot’ as US continues frantic search
TEL AVIV, Israel (AP) — The U.S. military pressed ahead Saturday in a frantic search for a missing…
#NewsBeep #News #BreakingNews #breakingnews #ground #invasion #Iran #Israel #Jets #killed #pilots #saturday #troops #Trump #War
https://www.newsbeep.com/468392/ -
Quantization from the Ground Up
https://ngrok.com/blog/quantization
#HackerNews #Quantization #Ground #Up #Machine #Learning #AI #Technology #Blog
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I Don't Hate Iran War, I Will if We Put Boots on Ground
https://misryoum.com/us/us/i-dont-hate-iran-war-i-will-if/
During his opening monologue on Friday’s broadcast of HBO’s “Real Time,” host Bill Maher said that if President Donald Trump “puts boots on the ground, yeah, then I’ll hate it. Now, I know too many happy Iranian Americans. Sorry....
#Dont #Hate #Iran #War #Will #Put #Boots #Ground #US_News_Hub #misryoum_com
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Iraqi Kurds Deny Role in Iran as Rumors Swirl of Kurdish Ground Invasion
https://misryoum.com/us/today/iraqi-kurds-deny-role-in-iran-as-rumors/
The Kurdistan Regional Government (KRG) of Iraq categorically denied that its Peshmerga were preparing an invasion of Iran alongside the United States on Thursday, following rumors that some Iranian Kurdish groups are planning ground operations on what remains of...
#Iraqi #Kurds #Deny #Role #Iran #Rumors #Swirl #Kurdish #Ground #Invasion #US_News_Hub #misryoum_com
