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#lpf — Public Fediverse posts

Live and recent posts from across the Fediverse tagged #lpf, aggregated by home.social.

  1. Spectral Filth: Clean Up Your Signal or Shut it Down

    1,563 words, 8 minutes read time.

    The spectrum is a finite piece of territory, and right now, you’re squatting on it like a man who doesn’t know how to clean his own house. Amateur radio used to be the domain of builders—men who understood that every watt of power was a responsibility. Now, the bands are crawling with appliance operators who treat their rigs like smartphones. They buy a cheap, unbranded box from overseas, hook it up to a sub-par antenna, and start spraying RF across the band like a broken sewer pipe. This isn’t just a technical oversight; it’s a failure of discipline. If your transmitter is throwing spurious emissions, you aren’t a radio operator. You’re a source of pollution. You are the high-frequency equivalent of a neighbor who lets his trash blow into everyone else’s yard. It’s time to stop making excuses, stop blaming the ionosphere for your lack of reach, and start looking at the cold, hard physics of what is actually coming out of your feedline.

    THE GUTLESS REALITY OF NON-LINEAR TRASH

    When you push a signal through an amplifier, you’re engaging in a fight with physics. If that amplifier isn’t biased correctly—if you’re driving it into saturation because you’re obsessed with the “100W” glowing on your meter—you are creating harmonics. These are the bastard children of your fundamental frequency. You think you’re sitting pretty on 7.150 MHz, but because your hardware is junk or your settings are sloppy, you’re also screaming on 14.300 MHz and 21.450 MHz. This is non-linear distortion, and it is the mark of a man who hasn’t mastered his tools. A real operator knows that the “final” in his radio is a delicate balance of current and voltage. When you push it too hard, the peaks flatten out, the sine wave turns into a jagged mess, and the resulting spectral splatter is an embarrassment. You aren’t just taking up more space than you’re entitled to; you’re stepping on the weak-signal guys three states over who are actually trying to do something meaningful with their license. If you can’t run a clean signal at full power, back the gain off. Mastery isn’t about being the loudest voice in the room; it’s about being the most precise.

    SHIELDING, STRAY INDUCTANCE, AND THE COST OF LAZINESS

    RF is a restless beast. It doesn’t want to stay on the copper traces of your PCB. It wants to radiate from every unshielded wire, every loose screw, and every poorly grounded chassis. If your hardware looks like a bird’s nest inside, you have already lost the war. Spurious emissions aren’t always harmonics; sometimes they’re parasitic oscillations—high-frequency ghosts born from the stray inductance of long lead wires and the lack of proper bypassing. When you skimp on the build quality, or when you use a switching power supply that hasn’t been filtered for common-mode noise, you are inviting filth into your signal. You wouldn’t drive a car with a leaking fuel line, so why are you operating a radio that leaks RF from its own casing? Every milliwatt that doesn’t go out the antenna port as a clean fundamental frequency is a milliwatt that is working against you. It creates RFI in your own shack, it trips your GFCI breakers, and it makes you a nuisance to your neighbors. You need to understand the mechanics of shielding. A chassis isn’t just a box to hold the components; it’s a Faraday cage. If you’ve compromised that cage because you were too lazy to tighten the bolts or use proper EMI gaskets, you are the problem.

    THE GATEKEEPERS: BUYING VS. BUILDING YOUR DEFENSES

    If you’re running a high-power station—pushing a kilowatt or more—you don’t play games with homebrew experiments unless you have the lab equipment to back it up. At those levels, the heat and reactive power in a filter are enough to turn cheap components into shrapnel. You buy a commercial Low-Pass Filter (LPF) from the outfits that build them like tanks—Bencher, Barker & Williamson, or DX Engineering. You’re looking for a heavy-duty, shielded enclosure that guarantees at least 50dB to 60dB of attenuation at the second harmonic. This is your “Master Gatekeeper.” It’s the insurance policy that keeps your high-power harmonics from bleeding into every television and radio in a three-block radius. Buying a filter isn’t an admission of defeat; it’s a strategic decision to use a tested, calibrated tool to protect the integrity of the bands. However, if you want to call yourself a master of this craft, you eventually have to build. For low-power rigs or specialized band-pass needs, building your own filter is where the theory becomes reality. You don’t use junk-box parts. You use precision-wound toroids—T50-2 or T60-6 powdered iron—and high-voltage Silver Mica or NP0 capacitors. If you use cheap ceramic discs, your filter’s cutoff frequency will drift as soon as the components get warm, and you’ll watch your SWR climb while your signal turns back into trash. Building a Chebyshev or Elliptic filter forces you to understand the relationship between inductance and capacitance. It’s a rite of passage. But remember: you never put a homebrew filter on the air without verification. You use a Vector Network Analyzer (VNA) to sweep that circuit and prove it’s doing its job. You verify the insertion loss and you confirm the stopband. If you can’t prove it’s clean on the bench, it doesn’t touch the antenna.

    Whether you buy it or build it, the responsibility for what leaves your shack stops with you. You wouldn’t drive a truck with no mufflers through a quiet neighborhood at 3 AM, so don’t be the operator who thinks it’s okay to spray wide-band noise across the spectrum because you were too lazy to install a filter. A clean signal is the signature of a disciplined man. It shows you respect the physics of the medium and the rights of every other operator on the air. If you’re too cheap to buy a filter and too lazy to build one, do the world a favor and stay off the mic. The airwaves are a shared resource, not your personal dumping ground. Every time you key up, your reputation is on the line. Are you a technical asset, or are you just more noise? Real operators don’t guess; they measure. They don’t hope; they verify. Master your hardware, tighten your shielding, and for the sake of the hobby, clean up your signal. If you can’t operate with technical integrity, you shouldn’t be operating at all. Solder the solution or shut it down.

    SECURE THE SPECTRUM: LOCK DOWN YOUR SIGNAL INTEGRITY NOW

    Stop being a spectator in your own shack. If you’ve spent more time looking at the price tag of your rig than the spectral purity of its output, you’re part of the problem. Your license isn’t a trophy; it’s a mandate to maintain technical excellence. If you aren’t checking your footprint, you’re just another lid adding to the noise floor.

    Here is your mission:

    • Audit your signal: Stop trusting the factory sticker. Put your rig on a dummy load, grab a VNA or a spectrum analyzer, and prove to yourself that your second and third harmonics aren’t bleeding into territory where they don’t belong.
    • Kill the noise: If you find filth, fix it. Solder a low-pass filter, choke your lines with real ferrites, and tighten every screw on your chassis until that Faraday cage is airtight.
    • Educate the soft: When you hear an operator splashing across the band with a dirty signal, don’t just complain about it on a forum. Direct him to the physics. Demand better from your local club.

    The grid is fragile and the noise floor is rising. We need operators who are assets, not liabilities. Clean up your signal today, or pull the plug. The airwaves don’t owe you a thing—you owe them your discipline. Own your frequency or get off it.

    SUPPORTSUBSCRIBECONTACT ME

    D. Bryan King

    Sources

    Disclaimer:

    The views and opinions expressed in this post are solely those of the author. The information provided is based on personal research, experience, and understanding of the subject matter at the time of writing. Readers should consult relevant experts or authorities for specific guidance related to their unique situations.

    Related Posts

    Rate this:

    #AmateurRadio #AmateurRadioTechnical #AmplifierBiasing #BandPassFilter #ChebyshevFilter #CommonModeCurrent #electromagneticInterference #EllipticFilter #Elmering #EMI #FaradayCage #FCCRegulations #FerriteChokes #hamRadio #HarmonicDistortion #HighPowerRF #IMD #IntermodulationDistortion #LinearElectronics #LowPassFilter #LPF #NonLinearAmplification #ParasiticOscillation #Part97Compliance #QRP #RadioHardware #radioSpectrumManagement #RadioStationAudit #RadioTransmitterMaintenance #RFEngineering #RFFeedback #RFFilterDesign #RFGrounding #RFPowerAmplifier #RFShielding #RFI #signalIntegrity #SignalPurity #SilverMicaCapacitors #SpectralFootprint #SpectralSplatter #SpectrumAnalysis #SpuriousEmissions #TechnicalDiscipline #TinySA #ToroidWinding #VectorNetworkAnalyzer #VNATesting
  2. Spectral Filth: Clean Up Your Signal or Shut it Down

    1,563 words, 8 minutes read time.

    The spectrum is a finite piece of territory, and right now, you’re squatting on it like a man who doesn’t know how to clean his own house. Amateur radio used to be the domain of builders—men who understood that every watt of power was a responsibility. Now, the bands are crawling with appliance operators who treat their rigs like smartphones. They buy a cheap, unbranded box from overseas, hook it up to a sub-par antenna, and start spraying RF across the band like a broken sewer pipe. This isn’t just a technical oversight; it’s a failure of discipline. If your transmitter is throwing spurious emissions, you aren’t a radio operator. You’re a source of pollution. You are the high-frequency equivalent of a neighbor who lets his trash blow into everyone else’s yard. It’s time to stop making excuses, stop blaming the ionosphere for your lack of reach, and start looking at the cold, hard physics of what is actually coming out of your feedline.

    THE GUTLESS REALITY OF NON-LINEAR TRASH

    When you push a signal through an amplifier, you’re engaging in a fight with physics. If that amplifier isn’t biased correctly—if you’re driving it into saturation because you’re obsessed with the “100W” glowing on your meter—you are creating harmonics. These are the bastard children of your fundamental frequency. You think you’re sitting pretty on 7.150 MHz, but because your hardware is junk or your settings are sloppy, you’re also screaming on 14.300 MHz and 21.450 MHz. This is non-linear distortion, and it is the mark of a man who hasn’t mastered his tools. A real operator knows that the “final” in his radio is a delicate balance of current and voltage. When you push it too hard, the peaks flatten out, the sine wave turns into a jagged mess, and the resulting spectral splatter is an embarrassment. You aren’t just taking up more space than you’re entitled to; you’re stepping on the weak-signal guys three states over who are actually trying to do something meaningful with their license. If you can’t run a clean signal at full power, back the gain off. Mastery isn’t about being the loudest voice in the room; it’s about being the most precise.

    SHIELDING, STRAY INDUCTANCE, AND THE COST OF LAZINESS

    RF is a restless beast. It doesn’t want to stay on the copper traces of your PCB. It wants to radiate from every unshielded wire, every loose screw, and every poorly grounded chassis. If your hardware looks like a bird’s nest inside, you have already lost the war. Spurious emissions aren’t always harmonics; sometimes they’re parasitic oscillations—high-frequency ghosts born from the stray inductance of long lead wires and the lack of proper bypassing. When you skimp on the build quality, or when you use a switching power supply that hasn’t been filtered for common-mode noise, you are inviting filth into your signal. You wouldn’t drive a car with a leaking fuel line, so why are you operating a radio that leaks RF from its own casing? Every milliwatt that doesn’t go out the antenna port as a clean fundamental frequency is a milliwatt that is working against you. It creates RFI in your own shack, it trips your GFCI breakers, and it makes you a nuisance to your neighbors. You need to understand the mechanics of shielding. A chassis isn’t just a box to hold the components; it’s a Faraday cage. If you’ve compromised that cage because you were too lazy to tighten the bolts or use proper EMI gaskets, you are the problem.

    THE GATEKEEPERS: BUYING VS. BUILDING YOUR DEFENSES

    If you’re running a high-power station—pushing a kilowatt or more—you don’t play games with homebrew experiments unless you have the lab equipment to back it up. At those levels, the heat and reactive power in a filter are enough to turn cheap components into shrapnel. You buy a commercial Low-Pass Filter (LPF) from the outfits that build them like tanks—Bencher, Barker & Williamson, or DX Engineering. You’re looking for a heavy-duty, shielded enclosure that guarantees at least 50dB to 60dB of attenuation at the second harmonic. This is your “Master Gatekeeper.” It’s the insurance policy that keeps your high-power harmonics from bleeding into every television and radio in a three-block radius. Buying a filter isn’t an admission of defeat; it’s a strategic decision to use a tested, calibrated tool to protect the integrity of the bands. However, if you want to call yourself a master of this craft, you eventually have to build. For low-power rigs or specialized band-pass needs, building your own filter is where the theory becomes reality. You don’t use junk-box parts. You use precision-wound toroids—T50-2 or T60-6 powdered iron—and high-voltage Silver Mica or NP0 capacitors. If you use cheap ceramic discs, your filter’s cutoff frequency will drift as soon as the components get warm, and you’ll watch your SWR climb while your signal turns back into trash. Building a Chebyshev or Elliptic filter forces you to understand the relationship between inductance and capacitance. It’s a rite of passage. But remember: you never put a homebrew filter on the air without verification. You use a Vector Network Analyzer (VNA) to sweep that circuit and prove it’s doing its job. You verify the insertion loss and you confirm the stopband. If you can’t prove it’s clean on the bench, it doesn’t touch the antenna.

    Whether you buy it or build it, the responsibility for what leaves your shack stops with you. You wouldn’t drive a truck with no mufflers through a quiet neighborhood at 3 AM, so don’t be the operator who thinks it’s okay to spray wide-band noise across the spectrum because you were too lazy to install a filter. A clean signal is the signature of a disciplined man. It shows you respect the physics of the medium and the rights of every other operator on the air. If you’re too cheap to buy a filter and too lazy to build one, do the world a favor and stay off the mic. The airwaves are a shared resource, not your personal dumping ground. Every time you key up, your reputation is on the line. Are you a technical asset, or are you just more noise? Real operators don’t guess; they measure. They don’t hope; they verify. Master your hardware, tighten your shielding, and for the sake of the hobby, clean up your signal. If you can’t operate with technical integrity, you shouldn’t be operating at all. Solder the solution or shut it down.

    SECURE THE SPECTRUM: LOCK DOWN YOUR SIGNAL INTEGRITY NOW

    Stop being a spectator in your own shack. If you’ve spent more time looking at the price tag of your rig than the spectral purity of its output, you’re part of the problem. Your license isn’t a trophy; it’s a mandate to maintain technical excellence. If you aren’t checking your footprint, you’re just another lid adding to the noise floor.

    Here is your mission:

    • Audit your signal: Stop trusting the factory sticker. Put your rig on a dummy load, grab a VNA or a spectrum analyzer, and prove to yourself that your second and third harmonics aren’t bleeding into territory where they don’t belong.
    • Kill the noise: If you find filth, fix it. Solder a low-pass filter, choke your lines with real ferrites, and tighten every screw on your chassis until that Faraday cage is airtight.
    • Educate the soft: When you hear an operator splashing across the band with a dirty signal, don’t just complain about it on a forum. Direct him to the physics. Demand better from your local club.

    The grid is fragile and the noise floor is rising. We need operators who are assets, not liabilities. Clean up your signal today, or pull the plug. The airwaves don’t owe you a thing—you owe them your discipline. Own your frequency or get off it.

    SUPPORTSUBSCRIBECONTACT ME

    D. Bryan King

    Sources

    Disclaimer:

    The views and opinions expressed in this post are solely those of the author. The information provided is based on personal research, experience, and understanding of the subject matter at the time of writing. Readers should consult relevant experts or authorities for specific guidance related to their unique situations.

    Related Posts

    Rate this:

    #AmateurRadio #AmateurRadioTechnical #AmplifierBiasing #BandPassFilter #ChebyshevFilter #CommonModeCurrent #electromagneticInterference #EllipticFilter #Elmering #EMI #FaradayCage #FCCRegulations #FerriteChokes #hamRadio #HarmonicDistortion #HighPowerRF #IMD #IntermodulationDistortion #LinearElectronics #LowPassFilter #LPF #NonLinearAmplification #ParasiticOscillation #Part97Compliance #QRP #RadioHardware #radioSpectrumManagement #RadioStationAudit #RadioTransmitterMaintenance #RFEngineering #RFFeedback #RFFilterDesign #RFGrounding #RFPowerAmplifier #RFShielding #RFI #signalIntegrity #SignalPurity #SilverMicaCapacitors #SpectralFootprint #SpectralSplatter #SpectrumAnalysis #SpuriousEmissions #TechnicalDiscipline #TinySA #ToroidWinding #VectorNetworkAnalyzer #VNATesting
  3. Spectral Filth: Clean Up Your Signal or Shut it Down

    1,563 words, 8 minutes read time.

    The spectrum is a finite piece of territory, and right now, you’re squatting on it like a man who doesn’t know how to clean his own house. Amateur radio used to be the domain of builders—men who understood that every watt of power was a responsibility. Now, the bands are crawling with appliance operators who treat their rigs like smartphones. They buy a cheap, unbranded box from overseas, hook it up to a sub-par antenna, and start spraying RF across the band like a broken sewer pipe. This isn’t just a technical oversight; it’s a failure of discipline. If your transmitter is throwing spurious emissions, you aren’t a radio operator. You’re a source of pollution. You are the high-frequency equivalent of a neighbor who lets his trash blow into everyone else’s yard. It’s time to stop making excuses, stop blaming the ionosphere for your lack of reach, and start looking at the cold, hard physics of what is actually coming out of your feedline.

    THE GUTLESS REALITY OF NON-LINEAR TRASH

    When you push a signal through an amplifier, you’re engaging in a fight with physics. If that amplifier isn’t biased correctly—if you’re driving it into saturation because you’re obsessed with the “100W” glowing on your meter—you are creating harmonics. These are the bastard children of your fundamental frequency. You think you’re sitting pretty on 7.150 MHz, but because your hardware is junk or your settings are sloppy, you’re also screaming on 14.300 MHz and 21.450 MHz. This is non-linear distortion, and it is the mark of a man who hasn’t mastered his tools. A real operator knows that the “final” in his radio is a delicate balance of current and voltage. When you push it too hard, the peaks flatten out, the sine wave turns into a jagged mess, and the resulting spectral splatter is an embarrassment. You aren’t just taking up more space than you’re entitled to; you’re stepping on the weak-signal guys three states over who are actually trying to do something meaningful with their license. If you can’t run a clean signal at full power, back the gain off. Mastery isn’t about being the loudest voice in the room; it’s about being the most precise.

    SHIELDING, STRAY INDUCTANCE, AND THE COST OF LAZINESS

    RF is a restless beast. It doesn’t want to stay on the copper traces of your PCB. It wants to radiate from every unshielded wire, every loose screw, and every poorly grounded chassis. If your hardware looks like a bird’s nest inside, you have already lost the war. Spurious emissions aren’t always harmonics; sometimes they’re parasitic oscillations—high-frequency ghosts born from the stray inductance of long lead wires and the lack of proper bypassing. When you skimp on the build quality, or when you use a switching power supply that hasn’t been filtered for common-mode noise, you are inviting filth into your signal. You wouldn’t drive a car with a leaking fuel line, so why are you operating a radio that leaks RF from its own casing? Every milliwatt that doesn’t go out the antenna port as a clean fundamental frequency is a milliwatt that is working against you. It creates RFI in your own shack, it trips your GFCI breakers, and it makes you a nuisance to your neighbors. You need to understand the mechanics of shielding. A chassis isn’t just a box to hold the components; it’s a Faraday cage. If you’ve compromised that cage because you were too lazy to tighten the bolts or use proper EMI gaskets, you are the problem.

    THE GATEKEEPERS: BUYING VS. BUILDING YOUR DEFENSES

    If you’re running a high-power station—pushing a kilowatt or more—you don’t play games with homebrew experiments unless you have the lab equipment to back it up. At those levels, the heat and reactive power in a filter are enough to turn cheap components into shrapnel. You buy a commercial Low-Pass Filter (LPF) from the outfits that build them like tanks—Bencher, Barker & Williamson, or DX Engineering. You’re looking for a heavy-duty, shielded enclosure that guarantees at least 50dB to 60dB of attenuation at the second harmonic. This is your “Master Gatekeeper.” It’s the insurance policy that keeps your high-power harmonics from bleeding into every television and radio in a three-block radius. Buying a filter isn’t an admission of defeat; it’s a strategic decision to use a tested, calibrated tool to protect the integrity of the bands. However, if you want to call yourself a master of this craft, you eventually have to build. For low-power rigs or specialized band-pass needs, building your own filter is where the theory becomes reality. You don’t use junk-box parts. You use precision-wound toroids—T50-2 or T60-6 powdered iron—and high-voltage Silver Mica or NP0 capacitors. If you use cheap ceramic discs, your filter’s cutoff frequency will drift as soon as the components get warm, and you’ll watch your SWR climb while your signal turns back into trash. Building a Chebyshev or Elliptic filter forces you to understand the relationship between inductance and capacitance. It’s a rite of passage. But remember: you never put a homebrew filter on the air without verification. You use a Vector Network Analyzer (VNA) to sweep that circuit and prove it’s doing its job. You verify the insertion loss and you confirm the stopband. If you can’t prove it’s clean on the bench, it doesn’t touch the antenna.

    Whether you buy it or build it, the responsibility for what leaves your shack stops with you. You wouldn’t drive a truck with no mufflers through a quiet neighborhood at 3 AM, so don’t be the operator who thinks it’s okay to spray wide-band noise across the spectrum because you were too lazy to install a filter. A clean signal is the signature of a disciplined man. It shows you respect the physics of the medium and the rights of every other operator on the air. If you’re too cheap to buy a filter and too lazy to build one, do the world a favor and stay off the mic. The airwaves are a shared resource, not your personal dumping ground. Every time you key up, your reputation is on the line. Are you a technical asset, or are you just more noise? Real operators don’t guess; they measure. They don’t hope; they verify. Master your hardware, tighten your shielding, and for the sake of the hobby, clean up your signal. If you can’t operate with technical integrity, you shouldn’t be operating at all. Solder the solution or shut it down.

    SECURE THE SPECTRUM: LOCK DOWN YOUR SIGNAL INTEGRITY NOW

    Stop being a spectator in your own shack. If you’ve spent more time looking at the price tag of your rig than the spectral purity of its output, you’re part of the problem. Your license isn’t a trophy; it’s a mandate to maintain technical excellence. If you aren’t checking your footprint, you’re just another lid adding to the noise floor.

    Here is your mission:

    • Audit your signal: Stop trusting the factory sticker. Put your rig on a dummy load, grab a VNA or a spectrum analyzer, and prove to yourself that your second and third harmonics aren’t bleeding into territory where they don’t belong.
    • Kill the noise: If you find filth, fix it. Solder a low-pass filter, choke your lines with real ferrites, and tighten every screw on your chassis until that Faraday cage is airtight.
    • Educate the soft: When you hear an operator splashing across the band with a dirty signal, don’t just complain about it on a forum. Direct him to the physics. Demand better from your local club.

    The grid is fragile and the noise floor is rising. We need operators who are assets, not liabilities. Clean up your signal today, or pull the plug. The airwaves don’t owe you a thing—you owe them your discipline. Own your frequency or get off it.

    SUPPORTSUBSCRIBECONTACT ME

    D. Bryan King

    Sources

    Disclaimer:

    The views and opinions expressed in this post are solely those of the author. The information provided is based on personal research, experience, and understanding of the subject matter at the time of writing. Readers should consult relevant experts or authorities for specific guidance related to their unique situations.

    Related Posts

    Rate this:

    #AmateurRadio #AmateurRadioTechnical #AmplifierBiasing #BandPassFilter #ChebyshevFilter #CommonModeCurrent #electromagneticInterference #EllipticFilter #Elmering #EMI #FaradayCage #FCCRegulations #FerriteChokes #hamRadio #HarmonicDistortion #HighPowerRF #IMD #IntermodulationDistortion #LinearElectronics #LowPassFilter #LPF #NonLinearAmplification #ParasiticOscillation #Part97Compliance #QRP #RadioHardware #radioSpectrumManagement #RadioStationAudit #RadioTransmitterMaintenance #RFEngineering #RFFeedback #RFFilterDesign #RFGrounding #RFPowerAmplifier #RFShielding #RFI #signalIntegrity #SignalPurity #SilverMicaCapacitors #SpectralFootprint #SpectralSplatter #SpectrumAnalysis #SpuriousEmissions #TechnicalDiscipline #TinySA #ToroidWinding #VectorNetworkAnalyzer #VNATesting
  4. Spectral Filth: Clean Up Your Signal or Shut it Down

    1,563 words, 8 minutes read time.

    The spectrum is a finite piece of territory, and right now, you’re squatting on it like a man who doesn’t know how to clean his own house. Amateur radio used to be the domain of builders—men who understood that every watt of power was a responsibility. Now, the bands are crawling with appliance operators who treat their rigs like smartphones. They buy a cheap, unbranded box from overseas, hook it up to a sub-par antenna, and start spraying RF across the band like a broken sewer pipe. This isn’t just a technical oversight; it’s a failure of discipline. If your transmitter is throwing spurious emissions, you aren’t a radio operator. You’re a source of pollution. You are the high-frequency equivalent of a neighbor who lets his trash blow into everyone else’s yard. It’s time to stop making excuses, stop blaming the ionosphere for your lack of reach, and start looking at the cold, hard physics of what is actually coming out of your feedline.

    THE GUTLESS REALITY OF NON-LINEAR TRASH

    When you push a signal through an amplifier, you’re engaging in a fight with physics. If that amplifier isn’t biased correctly—if you’re driving it into saturation because you’re obsessed with the “100W” glowing on your meter—you are creating harmonics. These are the bastard children of your fundamental frequency. You think you’re sitting pretty on 7.150 MHz, but because your hardware is junk or your settings are sloppy, you’re also screaming on 14.300 MHz and 21.450 MHz. This is non-linear distortion, and it is the mark of a man who hasn’t mastered his tools. A real operator knows that the “final” in his radio is a delicate balance of current and voltage. When you push it too hard, the peaks flatten out, the sine wave turns into a jagged mess, and the resulting spectral splatter is an embarrassment. You aren’t just taking up more space than you’re entitled to; you’re stepping on the weak-signal guys three states over who are actually trying to do something meaningful with their license. If you can’t run a clean signal at full power, back the gain off. Mastery isn’t about being the loudest voice in the room; it’s about being the most precise.

    SHIELDING, STRAY INDUCTANCE, AND THE COST OF LAZINESS

    RF is a restless beast. It doesn’t want to stay on the copper traces of your PCB. It wants to radiate from every unshielded wire, every loose screw, and every poorly grounded chassis. If your hardware looks like a bird’s nest inside, you have already lost the war. Spurious emissions aren’t always harmonics; sometimes they’re parasitic oscillations—high-frequency ghosts born from the stray inductance of long lead wires and the lack of proper bypassing. When you skimp on the build quality, or when you use a switching power supply that hasn’t been filtered for common-mode noise, you are inviting filth into your signal. You wouldn’t drive a car with a leaking fuel line, so why are you operating a radio that leaks RF from its own casing? Every milliwatt that doesn’t go out the antenna port as a clean fundamental frequency is a milliwatt that is working against you. It creates RFI in your own shack, it trips your GFCI breakers, and it makes you a nuisance to your neighbors. You need to understand the mechanics of shielding. A chassis isn’t just a box to hold the components; it’s a Faraday cage. If you’ve compromised that cage because you were too lazy to tighten the bolts or use proper EMI gaskets, you are the problem.

    THE GATEKEEPERS: BUYING VS. BUILDING YOUR DEFENSES

    If you’re running a high-power station—pushing a kilowatt or more—you don’t play games with homebrew experiments unless you have the lab equipment to back it up. At those levels, the heat and reactive power in a filter are enough to turn cheap components into shrapnel. You buy a commercial Low-Pass Filter (LPF) from the outfits that build them like tanks—Bencher, Barker & Williamson, or DX Engineering. You’re looking for a heavy-duty, shielded enclosure that guarantees at least 50dB to 60dB of attenuation at the second harmonic. This is your “Master Gatekeeper.” It’s the insurance policy that keeps your high-power harmonics from bleeding into every television and radio in a three-block radius. Buying a filter isn’t an admission of defeat; it’s a strategic decision to use a tested, calibrated tool to protect the integrity of the bands. However, if you want to call yourself a master of this craft, you eventually have to build. For low-power rigs or specialized band-pass needs, building your own filter is where the theory becomes reality. You don’t use junk-box parts. You use precision-wound toroids—T50-2 or T60-6 powdered iron—and high-voltage Silver Mica or NP0 capacitors. If you use cheap ceramic discs, your filter’s cutoff frequency will drift as soon as the components get warm, and you’ll watch your SWR climb while your signal turns back into trash. Building a Chebyshev or Elliptic filter forces you to understand the relationship between inductance and capacitance. It’s a rite of passage. But remember: you never put a homebrew filter on the air without verification. You use a Vector Network Analyzer (VNA) to sweep that circuit and prove it’s doing its job. You verify the insertion loss and you confirm the stopband. If you can’t prove it’s clean on the bench, it doesn’t touch the antenna.

    Whether you buy it or build it, the responsibility for what leaves your shack stops with you. You wouldn’t drive a truck with no mufflers through a quiet neighborhood at 3 AM, so don’t be the operator who thinks it’s okay to spray wide-band noise across the spectrum because you were too lazy to install a filter. A clean signal is the signature of a disciplined man. It shows you respect the physics of the medium and the rights of every other operator on the air. If you’re too cheap to buy a filter and too lazy to build one, do the world a favor and stay off the mic. The airwaves are a shared resource, not your personal dumping ground. Every time you key up, your reputation is on the line. Are you a technical asset, or are you just more noise? Real operators don’t guess; they measure. They don’t hope; they verify. Master your hardware, tighten your shielding, and for the sake of the hobby, clean up your signal. If you can’t operate with technical integrity, you shouldn’t be operating at all. Solder the solution or shut it down.

    SECURE THE SPECTRUM: LOCK DOWN YOUR SIGNAL INTEGRITY NOW

    Stop being a spectator in your own shack. If you’ve spent more time looking at the price tag of your rig than the spectral purity of its output, you’re part of the problem. Your license isn’t a trophy; it’s a mandate to maintain technical excellence. If you aren’t checking your footprint, you’re just another lid adding to the noise floor.

    Here is your mission:

    • Audit your signal: Stop trusting the factory sticker. Put your rig on a dummy load, grab a VNA or a spectrum analyzer, and prove to yourself that your second and third harmonics aren’t bleeding into territory where they don’t belong.
    • Kill the noise: If you find filth, fix it. Solder a low-pass filter, choke your lines with real ferrites, and tighten every screw on your chassis until that Faraday cage is airtight.
    • Educate the soft: When you hear an operator splashing across the band with a dirty signal, don’t just complain about it on a forum. Direct him to the physics. Demand better from your local club.

    The grid is fragile and the noise floor is rising. We need operators who are assets, not liabilities. Clean up your signal today, or pull the plug. The airwaves don’t owe you a thing—you owe them your discipline. Own your frequency or get off it.

    SUPPORTSUBSCRIBECONTACT ME

    D. Bryan King

    Sources

    Disclaimer:

    The views and opinions expressed in this post are solely those of the author. The information provided is based on personal research, experience, and understanding of the subject matter at the time of writing. Readers should consult relevant experts or authorities for specific guidance related to their unique situations.

    Related Posts

    Rate this:

    #AmateurRadio #AmateurRadioTechnical #AmplifierBiasing #BandPassFilter #ChebyshevFilter #CommonModeCurrent #electromagneticInterference #EllipticFilter #Elmering #EMI #FaradayCage #FCCRegulations #FerriteChokes #hamRadio #HarmonicDistortion #HighPowerRF #IMD #IntermodulationDistortion #LinearElectronics #LowPassFilter #LPF #NonLinearAmplification #ParasiticOscillation #Part97Compliance #QRP #RadioHardware #radioSpectrumManagement #RadioStationAudit #RadioTransmitterMaintenance #RFEngineering #RFFeedback #RFFilterDesign #RFGrounding #RFPowerAmplifier #RFShielding #RFI #signalIntegrity #SignalPurity #SilverMicaCapacitors #SpectralFootprint #SpectralSplatter #SpectrumAnalysis #SpuriousEmissions #TechnicalDiscipline #TinySA #ToroidWinding #VectorNetworkAnalyzer #VNATesting
  5. Spectral Filth: Clean Up Your Signal or Shut it Down

    1,563 words, 8 minutes read time.

    The spectrum is a finite piece of territory, and right now, you’re squatting on it like a man who doesn’t know how to clean his own house. Amateur radio used to be the domain of builders—men who understood that every watt of power was a responsibility. Now, the bands are crawling with appliance operators who treat their rigs like smartphones. They buy a cheap, unbranded box from overseas, hook it up to a sub-par antenna, and start spraying RF across the band like a broken sewer pipe. This isn’t just a technical oversight; it’s a failure of discipline. If your transmitter is throwing spurious emissions, you aren’t a radio operator. You’re a source of pollution. You are the high-frequency equivalent of a neighbor who lets his trash blow into everyone else’s yard. It’s time to stop making excuses, stop blaming the ionosphere for your lack of reach, and start looking at the cold, hard physics of what is actually coming out of your feedline.

    THE GUTLESS REALITY OF NON-LINEAR TRASH

    When you push a signal through an amplifier, you’re engaging in a fight with physics. If that amplifier isn’t biased correctly—if you’re driving it into saturation because you’re obsessed with the “100W” glowing on your meter—you are creating harmonics. These are the bastard children of your fundamental frequency. You think you’re sitting pretty on 7.150 MHz, but because your hardware is junk or your settings are sloppy, you’re also screaming on 14.300 MHz and 21.450 MHz. This is non-linear distortion, and it is the mark of a man who hasn’t mastered his tools. A real operator knows that the “final” in his radio is a delicate balance of current and voltage. When you push it too hard, the peaks flatten out, the sine wave turns into a jagged mess, and the resulting spectral splatter is an embarrassment. You aren’t just taking up more space than you’re entitled to; you’re stepping on the weak-signal guys three states over who are actually trying to do something meaningful with their license. If you can’t run a clean signal at full power, back the gain off. Mastery isn’t about being the loudest voice in the room; it’s about being the most precise.

    SHIELDING, STRAY INDUCTANCE, AND THE COST OF LAZINESS

    RF is a restless beast. It doesn’t want to stay on the copper traces of your PCB. It wants to radiate from every unshielded wire, every loose screw, and every poorly grounded chassis. If your hardware looks like a bird’s nest inside, you have already lost the war. Spurious emissions aren’t always harmonics; sometimes they’re parasitic oscillations—high-frequency ghosts born from the stray inductance of long lead wires and the lack of proper bypassing. When you skimp on the build quality, or when you use a switching power supply that hasn’t been filtered for common-mode noise, you are inviting filth into your signal. You wouldn’t drive a car with a leaking fuel line, so why are you operating a radio that leaks RF from its own casing? Every milliwatt that doesn’t go out the antenna port as a clean fundamental frequency is a milliwatt that is working against you. It creates RFI in your own shack, it trips your GFCI breakers, and it makes you a nuisance to your neighbors. You need to understand the mechanics of shielding. A chassis isn’t just a box to hold the components; it’s a Faraday cage. If you’ve compromised that cage because you were too lazy to tighten the bolts or use proper EMI gaskets, you are the problem.

    THE GATEKEEPERS: BUYING VS. BUILDING YOUR DEFENSES

    If you’re running a high-power station—pushing a kilowatt or more—you don’t play games with homebrew experiments unless you have the lab equipment to back it up. At those levels, the heat and reactive power in a filter are enough to turn cheap components into shrapnel. You buy a commercial Low-Pass Filter (LPF) from the outfits that build them like tanks—Bencher, Barker & Williamson, or DX Engineering. You’re looking for a heavy-duty, shielded enclosure that guarantees at least 50dB to 60dB of attenuation at the second harmonic. This is your “Master Gatekeeper.” It’s the insurance policy that keeps your high-power harmonics from bleeding into every television and radio in a three-block radius. Buying a filter isn’t an admission of defeat; it’s a strategic decision to use a tested, calibrated tool to protect the integrity of the bands. However, if you want to call yourself a master of this craft, you eventually have to build. For low-power rigs or specialized band-pass needs, building your own filter is where the theory becomes reality. You don’t use junk-box parts. You use precision-wound toroids—T50-2 or T60-6 powdered iron—and high-voltage Silver Mica or NP0 capacitors. If you use cheap ceramic discs, your filter’s cutoff frequency will drift as soon as the components get warm, and you’ll watch your SWR climb while your signal turns back into trash. Building a Chebyshev or Elliptic filter forces you to understand the relationship between inductance and capacitance. It’s a rite of passage. But remember: you never put a homebrew filter on the air without verification. You use a Vector Network Analyzer (VNA) to sweep that circuit and prove it’s doing its job. You verify the insertion loss and you confirm the stopband. If you can’t prove it’s clean on the bench, it doesn’t touch the antenna.

    Whether you buy it or build it, the responsibility for what leaves your shack stops with you. You wouldn’t drive a truck with no mufflers through a quiet neighborhood at 3 AM, so don’t be the operator who thinks it’s okay to spray wide-band noise across the spectrum because you were too lazy to install a filter. A clean signal is the signature of a disciplined man. It shows you respect the physics of the medium and the rights of every other operator on the air. If you’re too cheap to buy a filter and too lazy to build one, do the world a favor and stay off the mic. The airwaves are a shared resource, not your personal dumping ground. Every time you key up, your reputation is on the line. Are you a technical asset, or are you just more noise? Real operators don’t guess; they measure. They don’t hope; they verify. Master your hardware, tighten your shielding, and for the sake of the hobby, clean up your signal. If you can’t operate with technical integrity, you shouldn’t be operating at all. Solder the solution or shut it down.

    SECURE THE SPECTRUM: LOCK DOWN YOUR SIGNAL INTEGRITY NOW

    Stop being a spectator in your own shack. If you’ve spent more time looking at the price tag of your rig than the spectral purity of its output, you’re part of the problem. Your license isn’t a trophy; it’s a mandate to maintain technical excellence. If you aren’t checking your footprint, you’re just another lid adding to the noise floor.

    Here is your mission:

    • Audit your signal: Stop trusting the factory sticker. Put your rig on a dummy load, grab a VNA or a spectrum analyzer, and prove to yourself that your second and third harmonics aren’t bleeding into territory where they don’t belong.
    • Kill the noise: If you find filth, fix it. Solder a low-pass filter, choke your lines with real ferrites, and tighten every screw on your chassis until that Faraday cage is airtight.
    • Educate the soft: When you hear an operator splashing across the band with a dirty signal, don’t just complain about it on a forum. Direct him to the physics. Demand better from your local club.

    The grid is fragile and the noise floor is rising. We need operators who are assets, not liabilities. Clean up your signal today, or pull the plug. The airwaves don’t owe you a thing—you owe them your discipline. Own your frequency or get off it.

    SUPPORTSUBSCRIBECONTACT ME

    D. Bryan King

    Sources

    Disclaimer:

    The views and opinions expressed in this post are solely those of the author. The information provided is based on personal research, experience, and understanding of the subject matter at the time of writing. Readers should consult relevant experts or authorities for specific guidance related to their unique situations.

    Related Posts

    Rate this:

    #AmateurRadio #AmateurRadioTechnical #AmplifierBiasing #BandPassFilter #ChebyshevFilter #CommonModeCurrent #electromagneticInterference #EllipticFilter #Elmering #EMI #FaradayCage #FCCRegulations #FerriteChokes #hamRadio #HarmonicDistortion #HighPowerRF #IMD #IntermodulationDistortion #LinearElectronics #LowPassFilter #LPF #NonLinearAmplification #ParasiticOscillation #Part97Compliance #QRP #RadioHardware #radioSpectrumManagement #RadioStationAudit #RadioTransmitterMaintenance #RFEngineering #RFFeedback #RFFilterDesign #RFGrounding #RFPowerAmplifier #RFShielding #RFI #signalIntegrity #SignalPurity #SilverMicaCapacitors #SpectralFootprint #SpectralSplatter #SpectrumAnalysis #SpuriousEmissions #TechnicalDiscipline #TinySA #ToroidWinding #VectorNetworkAnalyzer #VNATesting
  6. Are you interested in the #LPF, the #FPÖ, the #DF, the #FrP (Norway)? T. Akkerman. “Anti-immigration Parties and the Defence of Liberal Values. The Exceptional Case of the List Pim Fortuyn”. In: Journal of Political Ideologies 10.3 (2005), pp. 337-354.

  7. europesays.com/ro/68573/ 12 echipe în Liga 1 / Președintele LPF vrea să reducă drastic numărul cluburilor: „Vom pune condiții mai dure la licențiere” #echipe #GinoIorgulescu #Liga1 #lpf #reducere #RO #Română #Romania #Romanian #Sport #Sports

  8. Are you interested in the #LPF? J. J. van Holsteyn, G. A. Irwin, and J. M. den Ridder. “In the Eye of the Beholder: The Perception of the List Pim Fortuyn and the Parliamentary Elections of May 2002”. In: Acta Politica 38 (2003), pp. 69-87.

  9. Want to know more about the #LPF? P. Schafraad, P. L. H. Scheepers, and F. P. Wester. “Media Attention to Fortuyn and LPF During the 2002 Elections Negative Bias or Following the News Routines?” In: Meaningful Media: Communication Research on the Social Construction of Reality.

  10. Simple PWM Filter PCB Build Guide

    Here are the build notes for my Simple PWM Filter PCB Design. Below you can see it connected to my Pico Touch Board.

    Warning! I strongly recommend using old or second hand equipment for your experiments.  I am not responsible for any damage to expensive instruments!

    If you are new to electronics and microcontrollers, see the Getting Started pages.

    Bill of Materials

    • PWM Audio Filter PCB (GitHub link below)
    • 2x Suitable filter components, for example, per channel:
      • 3x 1KΩ resistors
      • 2x 100nF ceramic capacitor
      • 1x 2u2 electrolytic capacitor
    • Optional: Pin headers
    • Optional: 2x 3.5mm TRS sockets (pcb mounted, see photos for footprint)

    Build Steps

    Taking a typical “low to high” soldering approach, this is the suggested order of assembly:

    • All resistors.
    • TRS sockets (if used).
    • Disc capacitors.
    • 3-way jumper headers (if used).
    • Electrolytic capacitors.

    Here are some build photos.

    If the electrolytic capacitors will be bent over, then they should be bent and soldered in place before the header pins.

    Testing

    I recommend performing the general tests described here: PCBs.

    PCB Errata

    There are no known issues with this PCB at present.

    Enhancements:

    • As previously mentioned it might have been useful to label the left and right channels and use the alternative resistor circuit symbol.
    • It might have been useful to include solder jumpers to allow the simple combining of the left and right inputs and outputs
    • Some additional connection points for an oscilloscope might have been useful too.

    Find it on GitHub here.

    Sample Applications

    Here are some applications to get started with:

    Experimenter board

    Rather than fixed components, it is possible to solder on round pin header sockets to allow components to be pushed into place. This means that it is fairly easy to experiment with alternative component values to see what difference they make.

    When doing this, I only soldered up one channel, but joined the left/right inputs and outputs by adding a solder bridge across the pin headers. I also soldered additional pins to the spare GND connections from the second channel. This allows plenty of pin connections for an oscilloscope.

    The connections for components aren’t as tight as they could be, especially for low-wattage components with pretty thin legs.

    It might be that just continuing to use solderless breadboard for experiments is simpler, but it was pretty useful to be able to leave oscilloscope connections and the input and output connected whilst experimenting.

    Board Manufacturing

    These boards are sized to allow them to be ordered in a 2×4 panel if required, and still remain within a 100x100mm footprint. I used jlcpcb’s panel options with v-cuts and it was really quite inexpensive to do.

    Closing Thoughts

    I’m still not sure I really understand enough analog electronics to get the theory of how a dual-stage filter incorporating a potential divider still works, and any simulation is still not quite matching my theory to experiment.

    As has been said, “in theory, theory and practice are the same, in practice they are different”.

    This might make some proper practicing a bit easier.

    Kevin

    #filter #lpf #pcb #pwm

  11. Simple PWM Filter PCB Design

    Having spent a bit of time attempting (although I’m not sure I’m succeeding yet) to understand how to get a useful filter for my Pico Touch Board Audio, I thought it would be useful to have a simple template PCB that could be used for a range of PWM low-pass filtering options.

    This is my design.

    Warning! I strongly recommend using old or second hand equipment for your experiments.  I am not responsible for any damage to expensive instruments!

    If you are new to electronics and microcontrollers, see the Getting Started pages.

    The Circuit

    This is following on from the discussion in Pico Touch Board Audio creating the template for a simple two-stage low-pass filter with an option for including a potential divider resistor to drop the overall voltage too.

    I’ve doubled the circuit to allow for stereo in and out if required and have included both 3.5mm TRS sockets and pin jumper headers for both input and output.

    It requires no power, being a completely passive filter.

    If stereo is not required, then just one of the circuits can be populated – ideally the one connected to the TRS tip.

    PCB Design

    There isn’t much to this pcb layout really. I was particularly keen to keep the PCB away from specific values of components, so instead used the silkscreen to present a pseudo-circuit diagram to make it clear which components are which.

    I’ve also tried to leave enough room for the electrolytic capacitors to allow them to be bent over if required.

    Closing Thoughts

    With hindsight, I can think of a couple of additions that would have been useful on the silkscreen – labelling which circuit is left and right for example.

    And having the boards back, I should have added manual “wavy line” resistor diagrams rather than rectangles, but it is enough for what I need.

    And it might have been useful to include some additional test points for connecting an oscilloscope.

    Kevin

    #filter #lpf #pcb #pwm

  12. Are you interested in the #LPF? E. Dinas and J. van Spanje. “Crime Story. The Role of Crime and Immigration in the Anti-Immigration Vote”. In: Electoral Studies 30.4 (2011), pp. 658-671. dx.doi.org/10.1016/j.electstud.

  13. Are you interested in the #LPF? B. Castanho Silva. “Populist Radical Right Parties and Mass Polarization in the Netherlands”. In: European Political Science Review (2017), pp. 1-26. dx.doi.org/10.1017/S1755773917.

  14. Want to know more about the #LPF? H. Pellikaan, T. van der Meer, and S. L. de Lange. “The Road from a Depoliticized to a Centrifugal Democracy”. In: Acta Politica 38 (2003), pp. 23-49.

  15. Are you interested in the #LPF? B. Castanho Silva. “Populist Radical Right Parties and Mass Polarization in the Netherlands”. In: European Political Science Review (2017), pp. 1-26. dx.doi.org/10.1017/S1755773917.

  16. Are you interested in the #LPF? B. Castanho Silva. “Populist Radical Right Parties and Mass Polarization in the Netherlands”. In: European Political Science Review (2017), pp. 1-26. dx.doi.org/10.1017/S1755773917.

  17. Are you interested in the #LPF? M. Lubbers and A. Güveli. “Voting LPF: Stratification and the Varying Importance of Attitudes”. In: Journal of Elections, Public Opinion and Parties 17.1 (2007), pp. 21-47. dx.doi.org/10.1080/13689880601.

  18. Want to know more about the #LPF? W. van der Brug. “How the LPF Fuelled Discontent. Empirical Tests of Explanations of LPF Support”. In: Acta Politica 38 (2003), pp. 89-106. dx.doi.org/10.1057/palgrave.ap.

  19. Goh. Wat doet #NSC toch aan #LPF denken.

    Messianistische partij, die even een magneet voor uitgerangeerde politici van de derde garnituur, ontspoorde pseudointellectuelen en opportunisten (mix&match) is.

    En dan uiteenvalt als de messias verflauwt.

  20. Are you interested in the #LPF, the #PVV? S. L. de Lange and D. Art. “Fortuyn versus Wilders: An Agency-Based Approach to Radical Right Party Building”. In: West European Politics 34.6 (2011), pp. 1229-1249. dx.doi.org/10.1080/01402382.20.

  21. @RoosVonk groot gemaakt door de corrupte media. Zoals #fortuyn #lpf #leefbaar #fvd #pvv #bbb en ondersteund door de #yesilgoz #vvd retoriek over asielzoekers. Corrupt omdat de grote media in handen zijn van een handvol ceo’s met als enig objectief zoveel mogelijk geld verdienen in zo’n kort mogelijke tijd. In het #internet tijdperk betekent dat zoveel mogelijk #clicks

  22. Are you interested in the #LPF? W. van der Brug. “How the LPF Fuelled Discontent. Empirical Tests of Explanations of LPF Support”. In: Acta Politica 38 (2003), pp. 89-106. dx.doi.org/10.1057/palgrave.ap.

  23. @fonolog

    Bij mij wel in ieder geval. Het was verbijsterend, diep triest en desondanks soms van een hoog vermakelijkheidsgehalte. #LPF

  24. Ik moet ineens weer aan Winny de Jong en Philomena Bijlhout denken. #LPF

    youtube.com/watch?v=0k3OUX_6Yc

  25. #filters arrived today finally from Greece. Got two 30MHz #LPF from #SV1AFN, and got one attached to the back my 857D for testing.

    #hamradio