RF.Guru Incredible Lab Newsletter – Issue #22

June Starts with Chokes, Roofs, and the Sound of Solar Inverters Waking Up

 

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Early June: When the Station Meets Summer

By the start of June, the antennas are back in full use, the weather is less forgiving, and every weak assumption in the station starts getting louder. The roof gets hotter, the enclosures get tested, the feedlines settle into their real environment, and somewhere nearby an inverter decides the bands were too quiet.

That makes this a good moment to focus on the parts of RF that look simple until they are built outdoors: common-mode chokes, transformer losses, metallic roofs, vertical behavior, and measurement methods that feel convincing right up until they measure the wrong thing.

So this issue is about exactly that: what still holds once the system leaves the bench, meets weather, and has to work in the real world.

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Fresh Technical Insights

When a Common-Mode Choke Test Jig Measures the Jig
A timely reminder that a measurement setup can quietly become part of the result. If the jig dominates the behavior, the choke never really got its turn to speak.
🔗 https://shop.rf.guru/pages/when-a-common-mode-choke-test-jig-measures-the-jig

The 50 Ω / 150 Ω Common-Mode Choke Myth on Multiband Antennas
A neat-looking rule that breaks down once multiband antennas stop behaving like one tidy textbook load.
🔗 https://shop.rf.guru/pages/the-50-ohm-150-ohm-common-mode-choke-myth-on-multiband-antennas

Why S21 Can Look Right for Chokes but Still Be Wrong
Another example of how a familiar instrument reading can feel convincing while still answering the wrong question.
🔗 https://shop.rf.guru/pages/why-s21-can-look-right-for-chokes-but-still-be-wrong

Transformer Losses: A Reality Check
Broadband transformers are compromises, not miracles. This piece brings the discussion back to heat, stress, geometry, and actual operating conditions.
🔗 https://shop.rf.guru/pages/transformer-losses-a-reality-check

The Paper That Made Baluns Stop Being Magic
A welcome look at the point where transformer folklore gave way to clearer RF thinking and better engineering language.
🔗 https://shop.rf.guru/pages/the-paper-that-made-baluns-stop-being-magic

Transmission Losses Are Not Mismatch Losses
Two losses, two mechanisms, one confusion that still refuses to die.
🔗 https://shop.rf.guru/pages/transmission-losses-are-not-mismatch-losses

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Outdoor RF Reality

Outdoor RF Enclosures Built for Weather and Reliability
Summer is when pretty boxes become real test subjects. A good enclosure is not just about keeping rain out — it is about survivability, serviceability, and RF sanity.
🔗 https://shop.rf.guru/pages/outdoor-rf-enclosures-built-for-weather-and-reliability

Current Distribution in Inverted-L Antennas
A useful way to stop talking about inverted-L antennas as shapes and start talking about them as current systems.
🔗 https://shop.rf.guru/pages/current-distribution-in-inverted-l-antennas

Vertical Antenna on a Metal Roof
Sometimes a metal roof helps. Sometimes it dominates. Sometimes it changes the question entirely.
🔗 https://shop.rf.guru/pages/vertical-antenna-on-a-metal-roof

Why a Log-Periodic Antenna Is Less Pesky Around a Huge Metallic Roof
Not immune, not magical — just less easily pushed around by nearby metal than many simpler antenna types.
🔗 https://shop.rf.guru/pages/why-a-log-periodic-antenna-is-less-pesky-around-a-huge-metallic-roof

When 1/4-Wave and 5/8-Wave Verticals Are Similar — and When They Are Not
Another case where the slogan version of antenna theory hides the conditions that actually decide the result.
🔗 https://shop.rf.guru/pages/when-1-4-wave-and-5-8-wave-verticals-are-similar-and-when-they-are-not

A Near-Resonant Off-Center-Fed Antenna Is Still a Real Antenna
Because “not perfect” is not the same thing as “not valid,” even if some antenna arguments pretend otherwise.
🔗 https://shop.rf.guru/pages/a-near-resonant-off-center-fed-antenna-is-still-a-real-antenna

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Noise, Claims, and Modern RF Traps

Bad Solar Inverters
A seasonal classic: the sun comes out, the panels wake up, and the HF bands suddenly sound like an apology note from EMC compliance.
🔗 https://shop.rf.guru/pages/bad-solar-inverters

When Antenna Claims Outrun Antenna Physics
A useful antidote to the kind of marketing language that sounds bold precisely because it skipped the hard parts.
🔗 https://shop.rf.guru/pages/when-antenna-claims-outrun-antenna-physics

Meshtastic, MeshCore, 868 MHz, and the Ham Radio Trap
A timely look at where experimentation, regulation, and amateur-radio framing do not always line up the way people assume they do.
🔗 https://shop.rf.guru/pages/meshtastic-meshcore-868-mhz-and-the-ham-radio-trap

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer watching measurements and hearing the reasoning instead of inheriting another summer myth? Mark covers many of the same themes with calm explanations, practical demonstrations, and a very low tolerance for magical RF thinking.
🔗 Watch the featured videos from our collaboration

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If this issue leaves you slightly more suspicious of neat choke graphs, slightly more respectful of weatherproofing, and slightly less impressed by claims that arrived without current paths, loss analysis, or context — good.

That is a very healthy way to begin June.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #21

Mid-May: Return Paths, Remote Switches, and the Trouble with Tuning the Wrong Thing

 

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What Mid-May Does to Radio Amateurs

By mid-May, the ladders are back out, the grass is growing around the radials, and a suspicious number of operators are once again trying to solve system problems by adjusting the most visible part of the antenna.

That is usually when things get interesting. Not because RF changed, but because the season invites people back outside — where feedlines, return paths, radial fields, shack folklore, and “good enough” shortcuts all get tested by real installations instead of tidy diagrams.

So this issue is about exactly that: what the system is really doing, where the return current actually goes, and why a nice-looking shortcut often solves the wrong problem.

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Fresh Technical Insights

Why a Hybrid Radial System Makes Sense
A useful reminder that one radial system does not always have to do every job. Hybrid thinking often fits the real world better than purism.
🔗 https://shop.rf.guru/pages/why-a-hybrid-radial-system-makes-sense

Why End-Fed Antennas Often Seem More Forgiving About Choke Placement
The choke is not always doing the same job. Once you separate “stop current here” from “define the end of the return path,” the confusion starts to clear.
🔗 https://shop.rf.guru/pages/why-end-fed-antennas-often-seems-more-forgiving-about-choke-placement

Counterpoise, Ground Plane, and Monopole Antennas
Useful terms, dangerous shortcuts. Because half the argument usually starts when people use the same word for different current paths.
🔗 https://shop.rf.guru/pages/counterpoise-ground-plane-and-monopole-antennas

The Return Path Is Not the Other Hand
A good correction to one of ham radio’s most persistent metaphors: yes, every antenna system needs a return mechanism — no, it does not have to look like an equal second half.
🔗 https://shop.rf.guru/pages/the-return-path-is-not-the-other-hand

Radials Have Two Jobs: Most Vertical Myths Start by Confusing Them
Once you separate the jobs radials actually do, a lot of vertical folklore becomes much easier to dismantle.
🔗 https://shop.rf.guru/pages/radials-have-two-jobs-most-vertical-myths-start-by-confusing-them

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Practical RF Reality

Bias-T to Power and Control a Remote QRO RF Switch Can Be a Bad Idea
Convenient on paper, but at QRO every extra part in that path becomes part of the stress problem.
🔗 https://shop.rf.guru/pages/bias-t-to-power-and-control-a-remote-qro-rf-switch-can-be-a-bad-idea

The “Second Counterpoise” at the Shack
A thoughtful look at a persistent bit of shack folklore: is it RF engineering, or just another comforting add-on wire?
🔗 https://shop.rf.guru/pages/the-second-counterpoise-at-the-shack

A 1.8:1 Is Good Enough — A Second Tuner Solves the Wrong Problem
Not every mismatch deserves another box. Sometimes the station is already close enough, and the real issue is elsewhere.
🔗 https://shop.rf.guru/pages/a-1-8-1-is-good-enough-a-second-tuner-solves-the-wrong-problem

When Boat HF RFI Refuses to Behave: Jan’s Long Road to a Real Fix
A real-world case study in why serious RFI work is usually a process of elimination, not a one-evening miracle.
🔗 https://shop.rf.guru/pages/when-boat-hf-rfi-refuses-to-behave-jan-s-long-road-to-a-real-fix

Michel Spelier Wins the World Again on 160 Meters
A welcome reminder that top-band success is built on steady station refinement, not mystical hardware headlines.
🔗 https://shop.rf.guru/pages/michel-spelier-wins-the-world-again-on-160-meters

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Myths, Framing, and the Wrong Lessons

When Entertainment Outruns Engineering
Curiosity is useful. Confidently blending unrelated RF topics into one convenient story is less so.
🔗 https://shop.rf.guru/pages/when-entertainment-outruns-engineering

Hans Schantz, UWB Thinking, and the Limits of Ham-Radio Framing
A timely reminder that deep antenna thinking does not always fit neatly inside familiar amateur-radio shorthand.
🔗 https://shop.rf.guru/pages/hans-schantz-uwb-thinking-and-the-limits-of-ham-radio-framing

Please Stop Tuning Oaks
Because a tuner finding a match does not turn a living tree into a good antenna — and the tree did not ask for the experiment.
🔗 https://shop.rf.guru/pages/please-stop-tuning-oaks

Conjugate Match Is Not the Same as a 50 Ω Match
One of those distinctions that sounds academic right up until it saves you from making the wrong conclusion about a real antenna system.
🔗 https://shop.rf.guru/pages/conjugate-match-is-not-the-same-as-a-50-ohm-match

Conjugate Match Is Real. “Matched Everywhere” Usually Isn’t.
A careful cleanup of a long-running argument where terminology drift did as much damage as the RF itself.
🔗 https://shop.rf.guru/pages/conjugate-match-is-real-matched-everywhere-usually-isn-t

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer watching measurements and hearing the reasoning instead of inheriting another springtime myth? Mark covers many of the same themes with calm explanations, practical demonstrations, and a healthy resistance to magical thinking.
🔗 Watch the featured videos from our collaboration

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If this issue leaves you slightly more suspicious of neat metaphors, slightly less eager to add another tuner, and slightly more interested in what the return path is actually doing — good.

That is usually where useful RF progress starts.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #20

May Day, Coax Trays, and the Annual Return of Springtime RF Reality

 

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First of May, but Nothing Political

This issue goes out on the first of May — not as a manifesto, but as a seasonal observation. By now, the garden is waking up, ladders are coming out, feedlines are being rerouted, and somebody is once again wondering whether rolling up spare coax has ruined the antenna.

Spring has a way of pushing radio amateurs back outdoors, back onto roofs, and back into the yearly rituals of bonding, grounding, tuning, and quietly distrusting old myths. That makes May 1 a perfectly good day for a newsletter like this: less ideology, more coax, fewer slogans, and a healthy respect for lightning season.

So this issue is about exactly that: spring maintenance, recurring SWR folklore, tuner symmetry myths, and the annual reminder that RF systems do not fix themselves.

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Fresh Technical Insights

Rolling Up Coax Is Not the Problem
A useful correction for one of the most persistent feedline superstitions. The presence of a coil is not automatically the problem — context still matters.
🔗 https://shop.rf.guru/pages/rolling-up-coax-is-not-the-problem

Symmetric Tuner Network Does Not Automatically Mean Symmetric Currents
A symmetrical schematic can look comforting right up until the actual current paths refuse to cooperate.
🔗 https://shop.rf.guru/pages/symmetric-tuner-network-does-not-automatically-mean-symmetric-currents

A Symmetric Tuner Still Often Needs a 1:1 Current Balun with Open-Wire
Another reminder that geometry on paper and balance in the real installation are not the same thing.
🔗 https://shop.rf.guru/pages/a-symmetric-tuner-still-often-needs-a-1-1-current-balun-with-open-wire

Why 10 Meters Becomes the Problem Child in a 40–10 m Off-Center-Fed Dipole
A practical look at why one band can misbehave badly even when the rest of the antenna seems perfectly acceptable.
🔗 https://shop.rf.guru/pages/why-10-meters-becomes-the-problem-child-in-a-40-10-m-off-center-fed-dipole

EFHW Core Magic
A timely dismantling of the idea that ferrite cores somehow turn compromise installations into broadband miracles.
🔗 https://shop.rf.guru/pages/efhw-core-magic

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Spring Station Reality

Lightning Protection Is a System, Not a Switch
As soon as the season changes, this becomes urgent again: surge protection only works when the full system is designed to work together.
🔗 https://shop.rf.guru/pages/lightning-protection-is-a-system-not-a-switch

Lightning, Antennas, and the Myth of “Attracting” Strikes
A good example of how intuitive-sounding language often distorts what is really happening around tall conductors and storms.
🔗 https://shop.rf.guru/pages/lightning-antennas-and-the-myth-of-attracting-strikes

TinySA, and Mythical 50 Ohms
Measurement tools are useful right up to the point where people start assigning them magical certainty they never promised.
🔗 https://shop.rf.guru/pages/tinysa-and-mythical-50-ohms

Why the Blanket “High SWR Means Derate the Balun” Claim Falls Apart
An important reminder that power handling is not decided by one number alone, no matter how convenient that would be.
🔗 https://shop.rf.guru/pages/why-the-blanket-high-swr-means-derate-the-balun-claim-falls-apart

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Myths That Refuse to Die

The ARRL Antenna Book, SWR, and the Myths That Refuse to Die
Even respected references can become vehicles for oversimplified takeaways once the nuance gets stripped away.
🔗 https://shop.rf.guru/pages/the-arrl-antenna-book-swr-and-the-myths-that-refuse-to-die

The Myth of SWR Panic
A familiar seasonal condition: the meter moves, panic follows, and the wrong conclusion arrives first.
🔗 https://shop.rf.guru/pages/the-myth-of-swr-panic

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer to watch the measurements, hear the reasoning, and skip the annual spring crop of RF folklore? Mark covers many of the same themes with calm explanations, practical demonstrations, and a welcome shortage of magical thinking.
🔗 Watch the featured videos from our collaboration

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If this issue leaves you slightly less nervous about rolled coax, slightly more skeptical of “perfectly symmetric” tuner claims, and slightly more serious about lightning season — good.

That is a very reasonable way to start May.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #19

We Waited on Purpose — 18 Articles for April 18

 

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Why This One Didn’t Go Out on the 15th

We could have sent this issue on April 15. We did not.

Not because the mail server forgot us. Not because the ferrites were still cooling down. And not because someone somewhere was still insisting that a perfect SWR curve proves everything that matters.

We held this one back for World Amateur Radio Day on April 18 — and if there was ever a good excuse to break our usual rhythm, this was it. So for once, the number is not marketing fluff: 18 April, 18 articles.

Normally we distrust neat numerology in RF. This time, we allowed ourselves one carefully controlled exception.

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Fresh Technical Insights

Why Broadside Does Not Really Add Much in a Compact 4-Square Receive Array
A useful correction for anyone expecting broadside mode to unlock hidden magic in a physically compact receive array.
🔗 https://shop.rf.guru/pages/why-broadside-does-not-really-add-much-in-a-compact-4-square-receive-array

9-Circle vs 4-Square on 160, 80, and 40 Meters
More elements do not automatically mean better results. This compares two serious low-band receive concepts where geometry still rules.
🔗 https://shop.rf.guru/pages/9-circle-vs-4-square-on-160-80-and-40-meters

Fixed 45° / 90° Hybrids in a Receive 4-Square: Choosing the Right Spacing for 160, 80, and 40 Meters
Phasing networks do not rescue bad spacing. This one gets into the geometry that actually decides whether the array behaves.
🔗 https://shop.rf.guru/pages/fixed-45-90-hybrids-in-a-receive-4-square-choosing-the-right-spacing-for-160-80-and-40-meters

Front/Back and 0°: Why Phasing Still Needs a Convention
When a phasing discussion starts without a reference convention, confusion is guaranteed. This article restores some order.
🔗 https://shop.rf.guru/pages/front-back-and-0-why-phasing-still-needs-a-convention

SD Antenna: Clever, Compact HF Receive Beamforming — But Not Magic
A thoughtful look at a smart receive concept that deserves engineering respect, but not mythology.
🔗 https://shop.rf.guru/pages/sd-antenna-clever-compact-hf-receive-beamforming-but-not-magic

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Practical RF Reality

Why My Trusty Hytera Still Wins the Hotspot Test
Sometimes the “older, boring, reliable” radio still beats the newer options where it counts: actual audio and actual usability.
🔗 https://shop.rf.guru/pages/why-my-trusty-hytera-still-wins-the-hotspot-test

Escaping SMPS Hell: Cleaning Hotspot Audio with a USB Filter
Switch-mode noise keeps finding new ways into small stations. This is a practical fix for a problem many people misdiagnose.
🔗 https://shop.rf.guru/pages/escaping-smps-hell-cleaning-hotspot-audio-with-a-usb-filter

Where to Measure a Multiband Antenna with an Antenna Analyzer
An analyzer is only as useful as the point where you connect it. This article explains where measurement starts helping — and where it starts misleading.
🔗 https://shop.rf.guru/pages/where-to-measure-a-multiband-antenna-with-an-antenna-analyzer

Characteristic Impedance Is Not a Resistor
A basic idea that somehow keeps getting flattened into the wrong mental model. This one untangles it properly.
🔗 https://shop.rf.guru/pages/characteristic-impedance-is-not-a-resistor

Tools Every Ham Radio Operator Actually Needs
Not the fantasy bench. Not the influencer bench. Just the tools that genuinely earn their place.
🔗 https://shop.rf.guru/pages/tools-every-ham-radio-operator-actually-needs

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Field Antennas, Ground, and Why Reality Wins

Beverage vs BOG: The Real Differences, the Pros and Cons, and What Works Best in the Field
Two antennas that get compared casually but behave differently enough that the details matter — especially outside the brochure.
🔗 https://shop.rf.guru/pages/beverage-vs-bog-the-real-differences-the-pros-and-cons-and-what-works-best-in-the-field

The Antenna That Hates Good Ground: Why a Beverage Dies at the Beach
A perfect example of why “better ground” is not always better antenna performance.
🔗 https://shop.rf.guru/pages/the-antenna-that-hates-good-ground-why-a-beverage-dies-at-the-beach

Why 120 Radials Still Lose to an Inverted-L EFHW in the Real World
A reminder that heroic radial fields do not automatically beat smarter current distribution and better geometry.
🔗 https://shop.rf.guru/pages/why-120-radials-still-lose-to-an-inverted-l-efhw-in-the-real-world

Stop Asking One Antenna to Do Everything: A Better 80–10 m Strategy
One of the healthiest habits in station design is giving up on universal solutions before they waste too much of your time.
🔗 https://shop.rf.guru/pages/stop-asking-one-antenna-to-do-everything-a-better-80-10-m-strategy

The FCP on 80 Meters: When a Counterpoise Gets Mistaken for an Antenna
Another elegant example of how naming the wrong part of the system leads to the wrong conclusions.
🔗 https://shop.rf.guru/pages/the-fcp-on-80-meters-when-a-counterpoise-gets-mistaken-for-an-antenna

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Arguments, Analyzer Tricks, and Sales Pitches

John Portune’s Window Line Argument Fails at the Foundation
A good example of how a persuasive-sounding argument can collapse once the basic assumptions are examined.
🔗 https://shop.rf.guru/pages/john-portune-s-window-line-argument-fails-at-the-foundation

Finding the Best Feedline Length for a Doublet with an Antenna Analyzer
Yes, feedline length matters here — but only when you understand what the analyzer is really showing you.
🔗 https://shop.rf.guru/pages/finding-the-best-feedline-length-for-a-doublet-with-an-antenna-analyzer

GaN Polar Modulation: Why the 100 W Amp Pitch Falls Short
A sober look at a modern-sounding pitch that still has to answer to the same old RF constraints.
🔗 https://shop.rf.guru/pages/gan-polar-modulation-why-the-100-w-amp-pitch-falls-short

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer to celebrate the day by watching the measurements, hearing the reasoning, and skipping the magical claims? Mark covers many of the same themes with calm explanations, practical demonstrations, and a healthy resistance to RF folklore.
🔗 Watch the featured videos from our collaboration

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If this issue makes you a little more suspicious of miracle arrays, perfect ground, analyzer shortcuts, and one-size-fits-all antennas — good.

That is exactly the kind of mindset amateur radio deserves on April 18.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #18

No April Fools — Just Resonance Myths, Safe Distances, and the Trouble with Absolutes

 

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Why We Never Mail on April 1

There is a very good reason we do not send the RF.Guru newsletter on April 1.

If we publish an article titled Resonance Isn’t Efficiency, half the internet thinks it is satire. If we publish a piece about lightning protection, someone assumes the joke is hidden in the grounding diagram. And if we dare say “best doesn’t exist,” at least three people will suspect we have finally gone fully philosophical.

So no — we do not mail on April Fools’ Day. Not because we lack material, but because amateur radio already produces enough accidental comedy on its own. The rest of the year, we simply document it.

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Fresh Technical Insights

Why “Best” Doesn’t Exist
Antenna discussions love winners, rankings, and universal answers. Physics does not. This is the article for anyone still shopping for “the best” without first defining the problem.
🔗 https://shop.rf.guru/pages/why-best-doesn-t-exist

Resonance Isn’t Efficiency
A familiar but necessary correction: a nice match or a pretty dip in reactance does not tell you how well the antenna radiates.
🔗 https://shop.rf.guru/pages/resonance-isn-t-efficiency

Resonance, X = 0, and Radiation Resistance Are Different Things
Three concepts that keep getting flattened into one. This piece separates them cleanly and explains why that matters in real antenna work.
🔗 https://shop.rf.guru/pages/resonance-x-0-and-radiation-resistance-are-different-things

Resonance Isn’t Your Radiation Pattern
Because an antenna can be resonant and still launch energy in exactly the wrong places.
🔗 https://shop.rf.guru/pages/resonance-isn-t-your-radiation-pattern

Absolutes Stick, Nuance Dissolves
A short title that captures one of ham radio’s oldest problems: the simpler the claim, the further it often is from reality.
🔗 https://shop.rf.guru/pages/absolutes-stick-nuance-dissolves

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Practical Antenna Reality

Delta Loop vs Dipole Directionality
Pattern talk is easy until height, shape, and installation start mattering. This article compares the two in a way that actually survives contact with the real world.
🔗 https://shop.rf.guru/pages/delta-loop-vs-dipole-directionality

Efficient End-Fed Half-Waves on 17 m, 15 m, 12 m, and 10 m
Shorter HF bands give the EFHW more room to behave — if the design and installation still respect physics.
🔗 https://shop.rf.guru/pages/efficient-end-fed-half-waves-on-17-m-15-m-12-m-and-10-m

Low-Band EFHW Inverted-L
A practical low-band solution that works because of geometry, current distribution, and real-world tradeoffs — not because of miracle marketing.
🔗 https://shop.rf.guru/pages/low-band-efhw-inverted-l

My TX Antenna Strategy from 160 m to 4 m
A broader station view: different bands want different solutions, and pretending otherwise is how compromise turns into confusion.
🔗 https://shop.rf.guru/pages/my-tx-antenna-strategy-from-160-m-to-4-m

Raised Vertical Height for DX
Verticals are not just about radials and wishful thinking. Height above ground changes current distribution and launch angle in ways that matter for real DX work.
🔗 https://shop.rf.guru/pages/raised-vertical-height-for-dx

The EFHW8010 Is Not a Broadband Octave Antenna
One of those statements that sounds obvious once said out loud — yet still needs saying.
🔗 https://shop.rf.guru/pages/the-efhw8010-is-not-a-broadband-octave-antenna

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Feedlines, Ferrites, and Things People Keep Oversimplifying

Gluing Different Ferrite Mixes into One Coax Choke
A good example of where clever-looking ideas need real RF context before becoming real RF solutions.
🔗 https://shop.rf.guru/pages/gluing-different-ferrite-mixes-into-one-coax-choke

Why the One-Wire Spacing Rule for HF Window Line Is a Myth
Another neat rule of thumb that falls apart the moment you ask what assumptions it was built on.
🔗 https://shop.rf.guru/pages/why-the-one-wire-spacing-rule-for-hf-window-line-is-a-myth

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Safety, Power, and the Parts You Should Not Wing

QRO RF Safe Distance Guide for Common HF Antennas — 500 W to 1.5 kW
A timely reminder that “it tunes” and “it is safe” are very different statements.
🔗 https://shop.rf.guru/pages/qro-rf-safe-distance-guide-for-common-hf-antennas-500-w-1-5-kw

PE Safety and Antenna Bonding
Grounding discussions go wrong fast. This one keeps the safety side and the RF side in the right places.
🔗 https://shop.rf.guru/pages/pe-safety-and-antenna-bonding

Lightning Protection for HF Antennas — Halfway Measures Are Not a System
A surge protector without a real bonding and grounding strategy is not a system. It is optimism with hardware.
🔗 https://shop.rf.guru/pages/lightning-protection-for-hf-antennas-halfway-measures-are-not-a-system

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer to watch the measurements, hear the explanations, and skip the forum mythology? Mark covers many of the same themes with calm clarity, practical demonstrations, and a refreshingly low tolerance for magical thinking.
🔗 Watch the featured videos from our collaboration

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If this issue leaves you slightly less impressed by absolute claims, and slightly more interested in current paths, radiation patterns, and safety margins — good.

That is usually where the useful part of amateur radio begins.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #17

Specs, Signal Paths, and the Trouble with Reading Only the Headline

 

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When Numbers Start Looking Too Comfortable

By the time a spec sheet, lab report, or PDF starts circulating widely in ham radio, it often stops being read and starts being repeated.

This issue is about what happens next: ferrite data reduced to slogans, transceiver lab tests treated like final verdicts, connector ratings taken literally, and transformer designs copied as if context did not exist.

The recurring lesson is simple: measurements matter — but only when you understand what they actually measure.

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Fresh Technical Insights

Ferrite Tolerances Aren’t One Thing
Material variation is real, but it does not reduce to one neat percentage. This article explains which tolerances matter, when they matter, and why vague claims are not enough.
🔗 https://shop.rf.guru/pages/ferrite-tolerances-aren-t-one-thing

Where SFDR Shines
A useful reminder that no single performance number tells the whole story — but in the right context, SFDR really does matter.
🔗 https://shop.rf.guru/pages/where-sfdr-shines

FPGA Doesn’t Repeal Physics
Modern DSP can do impressive things, but it cannot erase overload, bad front ends, or the basic limits of analog RF design.
🔗 https://shop.rf.guru/pages/fpga-doesn-t-repeal-physics

Why Broadband RF Transformers Aren’t “Copy-and-Paste”
A transformer that works beautifully in one application can quietly fail in another. Turns ratio alone never tells the full story.
🔗 https://shop.rf.guru/pages/why-broadband-rf-transformers-aren-t-copy-and-paste

Top of the Bottom: Why 160 Meters Is “Top Band”
A small historical and technical detour into one of amateur radio’s most stubbornly named bands.
🔗 https://shop.rf.guru/pages/top-of-the-bottom-why-160-meters-is-top-band

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Practical RF Reality

How to Read Transceiver “Lab Test Reports”
Useful data only stays useful if you know what the tables mean — and what they do not mean once the radio leaves the bench.
🔗 https://shop.rf.guru/pages/how-to-read-transceiver-lab-test-reports

When “The Test” Becomes “The Truth”
One measurement, one setup, one conclusion… and suddenly it becomes doctrine. This piece is about resisting that temptation.
🔗 https://shop.rf.guru/pages/when-the-test-becomes-the-truth

Going QRO?
Power makes weak assumptions fail faster. Here’s what actually deserves attention before you simply turn the knob further clockwise.
🔗 https://shop.rf.guru/pages/going-qro

What Actually Limits Coax at QRO with High SWR
It is rarely just “the watts.” Voltage stress, current, dielectric heating, and mismatch all get a vote.
🔗 https://shop.rf.guru/pages/what-actually-limits-coax-at-qro-with-high-swr

Why PL-259 / SO-239 Power Ratings Need Derating
Catalog ratings are one thing. Real installations, real duty cycle, and real mismatch are another.
🔗 https://shop.rf.guru/pages/why-pl-259-so-239-power-ratings-need-derating

OS5Z “Dreamer” Antennas
A practical station example that reminds us that real performance comes from the full system, not just a neat headline number.
🔗 https://shop.rf.guru/pages/os5z-dreamer-antennas

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Legacy, Context, and Persistent Myths

LORAN: Why It Still Matters to Ham Radio
Old systems still have lessons to teach. This one connects legacy navigation thinking with modern amateur-radio perspective.
🔗 https://shop.rf.guru/pages/loran-why-it-still-matters-to-ham-radio

“Voltage-Fed” Antennas Aren’t Inherently More Dangerous Than a Dipole
Another example of a claim that sounds technical until you ask what it is actually comparing.
🔗 https://shop.rf.guru/pages/voltage-fed-antennas-aren-t-inherently-more-dangerous-than-a-dipole

Where DL4ZAO’s “Balun” PDF Derails
A careful look at where a widely cited document stops helping and starts misdirecting.
🔗 https://shop.rf.guru/pages/where-dl4zao-s-balun-pdf-derails

Sevick’s Transmission Line Transformers, Re-Read in 2026
Still essential, still worth reading, and still one of the few references that rewards being studied properly.
🔗 https://shop.rf.guru/pages/sevick-is-still-the-transformer-book

---

YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer watching measurements and explanations instead of arguing about screenshots and spec tables? Mark dives into many of the same RF topics with calm clarity, practical demonstrations, and zero tolerance for hand-wavy mythology.
🔗 Watch the featured videos from our collaboration

---

If this issue leaves you slightly more cautious around clean-looking charts, absolute claims, and copy-pasted transformer advice — good.

That is usually where better RF decisions begin.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #16

“It Depends.” Because RF Doesn’t Care About Simple Answers

 

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Late February: Where Definitions Start Fighting Back

By the end of February, the band conditions may change… but the questions do not. “Is my antenna balanced?” “Does grounding fix RF?” “Can I measure efficiency with my VNA?” And the perennial favorite: “How long is too long?”

This issue is a guided tour through the parts of RF people love to oversimplify: balanced vs unbalanced, antenna impedance vs line impedance, feedlines that behave like current machines, and why the environment is often the most important “circuit element” you forgot to model.

The core message is simple: if RF feels confusing, it’s usually because the setup is incomplete — not because the physics is mysterious.

---

Fresh Technical Insights

Why You Can’t Measure Antenna Efficiency with a VNA
VNAs are great tools — but efficiency isn’t one of the things they can directly tell you. Here’s why, and what measurements actually matter.
🔗 https://shop.rf.guru/pages/why-you-can-t-measure-antenna-efficiency-with-a-vna

Broadband HF Transformers
A practical look at what makes a transformer “broadband” in the real world — and what makes it quietly lossy.
🔗 https://shop.rf.guru/pages/broadband-hf-transformers

Why Feedlines Are “Current-Driven” in Normal 50-Ohm Operation
A key concept that explains half the misunderstandings around coax behavior, matching, and common-mode current.
🔗 https://shop.rf.guru/pages/why-feedlines-are-current-driven-in-normal-50-ohm-operation

How Long Is Too Long?
Cable length debates never die. This one explains where length really matters — and where it’s just superstition.
🔗 https://shop.rf.guru/pages/how-long-is-too-long

It Depends!
The most correct answer in RF, and the one people hate hearing. Here’s why context is the answer, not a footnote.
🔗 https://shop.rf.guru/pages/it-depends

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Balanced, Unbalanced, and “Unbalanced to What?”

Off-Center-Fed Dipole ≠ “Unbalanced Antenna”
OCFs aren’t automatically “unbalanced.” What matters is the reference and the return paths you create.
🔗 https://shop.rf.guru/pages/off-center-fed-dipole-unbalanced-antenna

“Unbalanced Antenna” Usually Means “Unbalanced to Ground”
A phrase that causes endless confusion. This piece defines it properly — and shows why it matters for feedline current.
🔗 https://shop.rf.guru/pages/unbalanced-antenna-usually-means-unbalanced-to-ground

600 Ω Ladder Line on an Off-Center-Fed Dipole
The line can be beautiful. The environment can ruin it. Here’s what works, what doesn’t, and why.
🔗 https://shop.rf.guru/pages/600-ohm-ladder-line-on-an-off-center-fed-dipole

600 Ω Open-Wire Line: Balanced by Design, Unbalanced by the Environment
Balanced lines stay balanced only if the environment lets them. This explains how symmetry is lost in real installs.
🔗 https://shop.rf.guru/pages/600-ohm-open-wire-line-balanced-by-design-unbalanced-by-the-environment

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Ground, “Ground,” and the Things People Hope It Will Fix

Floating Ground in AC Power Has a Meaning … in RF It Mostly Doesn’t
In safety and power systems, “ground” has purpose. In RF, it’s usually an abused word for a return path you didn’t model.
🔗 https://shop.rf.guru/pages/floating-ground-in-ac-power-has-a-meaning-in-rf-it-mostly-doesn-t

DC-Grounded Coax at HF: Why “Ground” Doesn’t Tame RF
DC continuity is not an RF solution. Here’s why “grounding the shield” doesn’t automatically stop common-mode current.
🔗 https://shop.rf.guru/pages/dc-grounded-coax-at-hf-why-ground-doesn-t-tame-rf

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Patterns, Impedance, and Real-World Directionality

Antenna Impedance vs. Transmission Line Impedance
Two different concepts that get blended into one argument. This separates them — and makes matching make sense again.
🔗 https://shop.rf.guru/pages/antenna-impedance-vs-transmission-line-impedance

Delta Loop vs Dipole Directionality
Directionality isn’t a slogan. It’s current distribution, height, and environment — and this compares the two properly.
🔗 https://shop.rf.guru/pages/delta-loop-vs-dipole-directionality

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RF Satire Corner

Measurement-Avoiditis
A chronic condition affecting many operators. Symptoms include absolute claims, zero measurements, and strong opinions.
🔗 https://shop.rf.guru/pages/measurement-avoiditis

---

YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer seeing the measurements instead of debating them? Mark breaks down many of these topics with calm explanations, clear demonstrations, and zero tolerance for RF mythology.
🔗 Watch the featured videos from our collaboration

---

If you take one thing from this issue, let it be this: “balanced” and “unbalanced” only mean something when you say: balanced to what?

And when someone answers a complex RF question with a single sentence… it’s okay to reply: “It depends.”

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #15

Feedlines, Phantom Conductors, and the Return of “Good Enough”

 

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February: Where Physics Gets Personal

By February, the honeymoon phase of the new year is over. The station hasn’t magically improved, the noise hasn’t disappeared, and the feedline still insists on participating in places it shouldn’t.

This issue dives deep into magnetizing inductance, phantom conductors, portable vertical claims, USB-C noise, and the uncomfortable reality that “good enough” is often just a polite way of saying “untested.”

If there’s a theme this month, it’s this: most RF problems aren’t mysterious — they’re measurable.

---

Fresh Technical Insights

High XL (Magnetizing Inductance) Is Great for Power Transfer…
Transformer design isn’t magic — high magnetizing reactance is fundamental. Here’s why it matters and how it’s often misunderstood.
🔗 https://shop.rf.guru/pages/high-xl-is-great-for-power-transfer

When the Feedline “Becomes the Antenna”?
It’s not mystical coupling — it’s common-mode current doing exactly what physics allows it to do.
🔗 https://shop.rf.guru/pages/when-the-feedline-becomes-the-antenna

The Phantom Third Conductor
Two conductors in theory. Three in practice. Understanding where that “extra” path comes from changes everything.
🔗 https://shop.rf.guru/pages/the-phantom-third-conductor

Coax Unbalanced by Definition?
Balanced vs unbalanced isn’t about connector count — it’s about reference and return paths.
🔗 https://shop.rf.guru/pages/coax-unbalanced-by-definition

G3TXQ “Common-Mode Chokes” Revisited
A fresh look at a classic reference — what still holds, what needs context.
🔗 https://shop.rf.guru/pages/g3txq-common-mode-chokes-revisited

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Practical RF Reality

Wire Antennas in a Small Garden
Constraints don’t prevent performance — poor geometry does.
🔗 https://shop.rf.guru/pages/wire-antennas-in-a-small-garden

Why “Antenna Loss Calculators” Aren’t That Useful
Spreadsheets don’t know your soil, height, or common-mode current.
🔗 https://shop.rf.guru/pages/why-antenna-loss-calculators-aren-t-that-useful

Why UHF Hotspots Often Beat VHF in a Tiny Room
Propagation physics changes indoors — and so should expectations.
🔗 https://shop.rf.guru/pages/why-uhf-hotspots-often-beat-vhf-in-a-tiny-room

A Room Full of PIMs (Not the Cookies)
Passive intermodulation isn’t just for towers — it can live in your shack too.
🔗 https://shop.rf.guru/pages/a-room-full-of-pims-not-the-cookies

USB Chargers, Power Supplies, and Why CM/DM Noise Feels Worse in the USB-C PD Era
Modern convenience brings modern noise. Understanding CM vs DM is step one.
🔗 https://shop.rf.guru/pages/usb-chargers-power-supplies-and-why-cm-dm-noise-feels-worse-in-the-usb-c-pd-era

Making AM Sound Better on an SDR
DSP can help — but only if you understand what it’s fixing.
🔗 https://shop.rf.guru/pages/making-am-sound-better-on-an-sdr

Good Enough Isn’t Good Enough Anymore
Because small inefficiencies compound — and modern RF environments are unforgiving.
🔗 https://shop.rf.guru/pages/good-enough-isn-t-good-enough-anymore

POTA PERformer — Challenger — Dominator — And the Real “Dominator”
Marketing tiers are easy. Real-world dominance is measurable.
🔗 https://shop.rf.guru/pages/pota-performer-challenger-dominator-and-the-real-dominator

A Portable Vertical Write-Up Starts as Engineering
If the first paragraph is hype instead of physics, be cautious.
🔗 https://shop.rf.guru/pages/a-portable-vertical-write-up-starts-as-engineering

The 96% SWR Myth
Reflected power math doesn’t equal radiated power reality.
🔗 https://shop.rf.guru/pages/the-96-swr-myth

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RF Satire Corner

The Official™ Book of Ham Radio Absolutes
Guaranteed correct in every situation — until someone keys up and says “Well, actually…”
🔗 https://shop.rf.guru/pages/the-official%E2%84%A2-book-of-ham-radio-absolutes

---

YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer hearing the explanation instead of arguing about it? Mark breaks down many of these same topics with calm clarity, real measurements, and zero tolerance for RF mythology.
🔗 Watch the featured videos from our collaboration

---

If this issue makes you slightly more skeptical of neat charts, clean SWR curves, and perfectly symmetrical waterfalls — good.

That’s where better RF decisions begin.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #14

Polar Plots, Picnic Tables, and the Price of Believing the Wrong Graph

 

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When Models Meet the Real World

By the end of January, something becomes very clear: antennas don’t fail in theory — they fail when theory meets grass, soil, picnic tables, feedlines, and expectations.

This issue is about that collision. Between NEC plots and real installations, between claimed gain and measurable results, and between elegant models and the wonderfully messy reality of amateur radio.

If there’s a theme running through this issue, it’s simple: measurements don’t care how convincing your story sounds.

---

Fresh Technical Insights

Polar Plot vs Picnic Table
What looks perfect in simulation often collapses once the antenna meets the real world. Here’s why environment beats elegance every time.
🔗 https://shop.rf.guru/pages/polar-plot-vs-picnic-table

NECtacy in the Park
When simulation worship replaces validation — and why NEC is a tool, not a religion.
🔗 https://shop.rf.guru/pages/nectacy-in-the-park

Counterpoise vs. Radials on HF: What’s the Difference?
Same copper, different physics. Understanding the difference changes how you design HF antennas.
🔗 https://shop.rf.guru/pages/counterpoise-vs-radials-on-hf-what-s-the-difference

“4 dB of Gain” From Two Radials?
If adding copper magically creates gain, physics owes us an apology. Here’s where the myth breaks down.
🔗 https://shop.rf.guru/pages/4-db-of-gain-from-two-radials

Symmetrical “Ghost” Signals or IMD?
Mirror images on the waterfall aren’t mysterious — they’re measurable. And usually self-inflicted.
🔗 https://shop.rf.guru/pages/symmetrical-ghost-signals-or-imd

Archaïc by Design: The Beautiful Mess of Amateur Repeater Networks
Redundant, fragile, brilliant — and still working decades later. A look at why repeater networks evolved the way they did.
🔗 https://shop.rf.guru/pages/archaic-by-design-the-beautiful-mess-of-amateur-repeater-networks

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Practical RF Reality

RF Circulator: what it is, what it’s meant for, and what hams can do with it
Not a magic shield, but a powerful tool — when used where it actually belongs.
🔗 https://shop.rf.guru/pages/rf-circulator-what-it-is-what-it-s-meant-for-and-what-hams-can-do-with-it

5-Pole Band-Pass Filters in a Multi-2 Station at 1.5 kW
Isolation isn’t optional once multiple transmitters share the same air. Here’s what works — and what quietly fails.
🔗 https://shop.rf.guru/pages/5-pole-band-pass-filters-in-a-multi-2-station-at-1-5-kw

Active E-Dipole Height Above Ground vs Performance
A few meters can mean the difference between hearing DX and hearing your neighbor’s PSU.
🔗 https://shop.rf.guru/pages/active-e-dipole-height-above-ground-vs-performance

Mounting Height vs Performance for a 1-Meter Wideband Vertical E-Probe
Height isn’t about gain — it’s about coupling, noise, and sanity.
🔗 https://shop.rf.guru/pages/mounting-height-vs-performance-for-a-1-meter-wideband-vertical-e-probe

The 15 cm “Cheat Disk”: Why We Prefer a Capacitive Hat on E-Probes
Small geometry changes, big electrical consequences.
🔗 https://shop.rf.guru/pages/the-15-cm-cheat-disk-why-we-prefer-a-capacitive-hat-on-e-probes

Stop Shopping by “#1”...
Rankings don’t design stations — understanding does.
🔗 https://shop.rf.guru/pages/stop-shopping-by-1

“Gain” Is Not a PIM Cure… It’s a Power Discount Coupon
More gain doesn’t fix non-linearity — it just hides it until it hurts more.
🔗 https://shop.rf.guru/pages/gain-is-not-a-pim-cure-it-s-a-power-discount-coupon

-153 dBc LOW-PIM, Mostly Irrelevant for Hams…
Impressive numbers, wrong problem. Context matters more than spec sheets.
🔗 https://shop.rf.guru/pages/153-dbc-low-pim-mostly-irrelevant-for-hams

Your Active Antenna Isn’t the Upgrade… This Is
Spoiler: the improvement isn’t at the antenna — it’s everywhere else.
🔗 https://shop.rf.guru/pages/your-active-antenna-isn-t-the-upgrade-this-is

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RF Satire Corner

The Poking Ape and the Ham Radio Crashed Course
Confidence grows faster than competence — especially when HamFluencers are involved.
🔗 https://shop.rf.guru/pages/the-poking-ape-and-the-ham-radio-crashed-course

Captain Radials Discovers WSPR and Invites Methodology Critique
A heroic journey into data… and a reminder that interpretation matters.
🔗 https://shop.rf.guru/pages/captain-radials-discovers-wspr-invites-methodology-critique

---

YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer watching real measurements instead of debating them? Mark breaks down many of the same topics with calm explanations, clear demonstrations, and zero tolerance for RF mythology.
🔗 Watch the featured videos from our collaboration

---

If this issue leaves you slightly more skeptical of clean plots, bold gain claims, and miracle radials — good.

That’s how better stations are built.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Analog HotSPOT – Image Update Announcement

Less Heat, Cleaner Audio, Fewer False Triggers

 

Important HotSPOT Image Update

This update applies to the RF.Guru Analog HotSPOT SVXLink image dated 2025-12-09.

If you are running an older image:
Please upgrade your image first before applying any configuration changes.

If you are already running the latest image:
https://github.com/Guru-RF/Analog-HotSPOT-SVXLink

Rerun:

sudo hotspot-config

This wil install bug fixes and new features!

Important: Several defaults have changed. Start from the new defaults and adjust step by step from there.

What Changed

RX CTCSS handling updated
RX now only listens to mapped talkgroup CTCSS tones. This significantly reduces CPU usage (and heat) and greatly lowers the chance of false CTCSS detection. Detection is also stricter than before.

Improved TX audio processing
DSP filters have been added on the TX path to improve intelligibility and consistency. Expect cleaner audio with better presence and control, without sounding processed or harsh.

Announcement level adjusted
The announcement gain has been lowered so it is now in line with normal repeater traffic, avoiding sudden loud level jumps.

HotSPOT frequency fix
An issue where the hotspot frequency was not applied correctly has been fixed.

Recommended Action

After updating and rerunning sudo hotspot-config, review your configuration carefully. Do not blindly copy old settings back in — the new defaults are intentional and optimized for stability, audio quality, and long-term reliability.

73,
Joeri – ON6URE
RF.Guru

RF.Guru Incredible Lab Newsletter – Issue #13

New Year, Same Noise Floor — Time to Listen Smarter

 

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A Quiet Start… or So We Hoped

A new year begins. Fresh logs, fresh plans, and the familiar hope that this year the noise will somehow be lower.

It never is.

So instead of promising miracles, this first issue of 2026 does what RF.Guru does best: reset expectations, sharpen understanding, and focus on the part of the station that actually decides whether you hear DX — the receive system.

From active antennas in impossible spaces to long-standing myths about noise, polarization, and dynamic range, this issue sets the tone for the year ahead: listen better, measure more, assume less.

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Fresh Technical Insights

House Noise Isn’t “Vertically Polarized”
A persistent myth finally put to rest. Noise doesn’t care about your antenna’s orientation — it couples wherever physics allows it.
🔗 https://shop.rf.guru/pages/house-noise-isn-t-vertically-polarized

Active Receive Antenna — When the Attic Is Your Only Option
Not ideal, but sometimes unavoidable. Here’s how to make attic RX work without amplifying misery.
🔗 https://shop.rf.guru/pages/active-receive-antenna-when-the-attic-is-your-only-option

Tuning Active Receive Antennas
Why tuning RX antennas is about linearity and balance — not chasing resonance.
🔗 https://shop.rf.guru/pages/tuning-active-receive-antennas

Is Japan on 80 Meters “Real Low-Band DX”?
A reality check on propagation, geography, and what actually makes low-band DX impressive.
🔗 https://shop.rf.guru/pages/is-japan-on-80-meters-real-low-band-dx

Contest OMs Ditched Their Verticals After This “No-Radials” Inverted-L
When ground losses dominate, changing geometry beats adding copper.
🔗 https://shop.rf.guru/pages/contest-oms-ditched-their-verticals-after-this-no-radials-inverted-l

Why (EFHW) Inverted-L Antennas Beat Ground Verticals on the Top Bands
Height, current distribution, and physics — not fashion — decide performance on 160/80 m.
🔗 https://shop.rf.guru/pages/why-inverted-l-antennas-beat-ground-verticals-on-the-top-bands

Does an Inverted-L EFHW Have a “Direction”?
Sometimes yes, often misunderstood, and never for the reasons people think.
🔗 https://shop.rf.guru/pages/does-an-inverted-l-efhw-have-a-direction

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Practical Receive Reality

Receive Antennas in a Nutshell
A clear, no-nonsense overview of RX antenna types, trade-offs, and realistic expectations.
🔗 https://shop.rf.guru/pages/receive-antennas-in-a-nutshell

Dynamic Range Still Matters
Especially on HF. Especially in noisy environments. Especially with active antennas.
🔗 https://shop.rf.guru/pages/dynamic-range-still-matters

Noise Figure on Active Receive Antennas at HF
Why obsessing over NF below the atmospheric noise floor misses the real problem entirely.
🔗 https://shop.rf.guru/pages/noise-figure-on-active-receive-antennas-at-hf

Small Active Receive Loops — Engineering Beats Brochures
Loop size, balance, and linearity matter far more than glossy marketing claims.
🔗 https://shop.rf.guru/pages/small-active-receive-loops-engineering-beats-brochures

E-Field vs H-Field Receive Antennas for 0–30 MHz
Understanding coupling mechanisms is the first step toward real noise reduction.
🔗 https://shop.rf.guru/pages/e-field-vs-h-field-receive-antennas-for-0-30-mhz

Even an Inverted-V Needs a Choke
Because symmetry on paper doesn’t stop common-mode currents in the real world.
🔗 https://shop.rf.guru/pages/even-an-inverted-v-needs-a-choke

Noise Coupled ≠ Noise Radiated
If you don’t know how noise enters your system, you’ll never remove it.
🔗 https://shop.rf.guru/pages/noise-coupled-noise-radiated

Why the PA0FRI “Coax Balun 1:4 and 1:1” Document Keeps Coming Back
Outdated models have long afterlives — especially when they feel intuitive.
🔗 https://shop.rf.guru/pages/why-the-pa0fri-coax-balun-1-4-and-1-1-document-keeps-coming-back

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RF Satire Corner

The Poking Ape and the Ham Radio Crashed Course
When confidence rises faster than understanding. A familiar story, now with TinySA and Baofeng Mini.
🔗 https://shop.rf.guru/pages/the-poking-ape-and-the-ham-radio-crashed-course

Heinrich von Resonanz
A historical figure who never existed — yet perfectly explains why resonance obsession refuses to die.
🔗 https://shop.rf.guru/pages/heinrich-von-resonanz

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer to start the year listening instead of reading? Let Mark’s calm, methodical explanations walk through many of these same topics — with measurements, visuals, and zero tolerance for RF mythology.
🔗 Watch the featured videos from our collaboration

---

A new year doesn’t require new antennas — it requires better understanding of the ones we already use.

If this issue helps you hear one weaker signal, identify one noise source, or stop chasing one false promise, it has already paid off.

73 and a quieter shack for 2026,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #12

The Year Physics Refused to Bend

 

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Year-End Notes from the Shack

December 31st. Logs are closing, fireworks are loading, and somewhere a ham is still convinced that a perfect SWR curve will fix everything.

This final issue of the year is unapologetically honest. No summaries, no soft landings — just the recurring themes of 2025 laid bare: EFHW misconceptions, feedlines behaving badly, common-mode currents doing exactly what physics says they will, and the uncomfortable truth that measurement beats belief every single time.

If there’s one takeaway from this year, it’s simple: antennas didn’t change — expectations did.

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Fresh Technical Insights

SWR – An Artifact from the Stone Age of Amateur Radio
Once useful, now dangerously overinterpreted. Why SWR survived longer than its usefulness — and what actually matters instead.
🔗 https://shop.rf.guru/pages/swr-an-artifact-from-the-stone-age-of-amateur-radio

Why Back-to-Back EFHW Measurements Keep Fooling People
A perfect example of how neat lab setups can completely misrepresent real-world behavior.
🔗 https://shop.rf.guru/pages/why-back-to-back-efhw-measurements-keep-fooling-people

The EFHW Shunt Capacitor – A Double-Edged Sword
It fixes one problem while hiding three others. Here’s why it keeps misleading even experienced builders.
🔗 https://shop.rf.guru/pages/the-efhw-shunt-capacitor-a-double-edged-sword

LC Matching vs EFHW Shunt Capacitors – Why These Are Not the Same Thing
Superficially similar, fundamentally different. Matching theory matters more than folklore.
🔗 https://shop.rf.guru/pages/lc-matching-vs-efhw-shunt-capacitors-why-these-are-not-the-same-thing

EFHW 80–10 and the Space Argument
Why “it fits” is not the same as “it works,” especially once height and current distribution enter the picture.
🔗 https://shop.rf.guru/pages/efhw-80-10-and-the-space-argument

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Practical RF Reality Checks

Your EFHW Isn’t Noisy — Your Feedline Is
A recurring support-ticket classic. The antenna gets blamed while the coax quietly does the damage.
🔗 https://shop.rf.guru/pages/your-efhw-isn-t-noisy-your-feedline-is

Why a Low EFHW Can Look Good on SWR
Low height hides loss. Loss hides problems. SWR smiles and nods politely.
🔗 https://shop.rf.guru/pages/why-a-low-efhw-can-look-good-on-swr

Low Feedpoint, Low Height? A Terminated Antenna Is the Smarter Choice
Sometimes efficiency isn’t the goal — predictability and noise control are.
🔗 https://shop.rf.guru/pages/low-feedpoint-low-height-a-terminated-antenna-is-the-smarter-choice

CMC Is the Biggest Problem in Ham Radio
Not propagation. Not power. Not modulation. Just uncontrolled currents going where they shouldn’t.
🔗 https://shop.rf.guru/pages/cmc-is-the-biggest-problem-in-ham-radio

Routing Coax for HF Antennas (1–30 MHz)
Routing is RF. Treating it as plumbing is how noise enters the shack.
🔗 https://shop.rf.guru/pages/routing-coax-for-hf-antennas-1-30-mhz

I’m Getting Across the Pond — So Why Can’t I Hear Anything Back?
The perfect year-end reminder: transmitting is easy. Receiving is the hard part.
🔗 https://shop.rf.guru/pages/i-m-getting-across-the-pond-so-why-can-t-i-hear-anything-back

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RF Satire Corner

The Formula
Because if you can reduce RF to one equation, you never have to measure anything again.
🔗 https://shop.rf.guru/pages/the-formula

Space Compromise Works “Good Enough”
The most dangerous phrase in antenna design — especially when repeated often enough.
🔗 https://shop.rf.guru/pages/space-compromise-works-good-enough

Why I Don’t Want an SDR – Ham Radio Is a Technical Dead End
Equal parts provocation and uncomfortable truth. Comments guaranteed.
🔗 https://shop.rf.guru/pages/why-i-don-t-want-an-sdr-ham-radio

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YouTube Spotlight — Mark K3ZD (“Ham Florida Man”)

Prefer to close the year listening instead of reading? Lean back and let Mark’s calm, methodical explanations cut through many of the same myths — this time with visuals, measurements, and zero tolerance for magical thinking.
🔗 Watch the featured videos from our collaboration

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As this year closes, one thing is clear: antennas didn’t fail, ferrites didn’t lie, and physics never changed its mind — only expectations did.

If 2025 taught us anything, it’s this: measure more, assume less, and never trust a clean SWR curve without asking why.

73 and a clear noise floor for the new year,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #11

Silent Nights, Noisy Shacks, and the Eternal Search for the Holy Grail Antenna

 

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Winter Reflections from the Shack

Outside, the lights are up, the nights are long, and the bands are… unpredictable. Inside the shack, it’s the usual seasonal mix: cold coax, warm soldering irons, and yet another debate about SWR, efficiency, and whether this antenna will finally solve everything.

This issue leans into the end-of-year mood: fewer miracles, more measurements, and a gentle reminder that physics doesn’t take holidays. Pour something warm, sit back, and enjoy a deep dive into what actually works — and what absolutely doesn’t.

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Fresh Technical Insights

The VP2E Antenna – What It Is, How It Works, and How It Compares
A calm, measurement-driven look at a popular design — stripped of folklore, hype, and wishful thinking.
🔗 https://shop.rf.guru/pages/the-vp2e-antenna-what-it-is-how-it-works-and-how-it-compares

Why the Y21 Method Does Not Lose 6 dB – A Clear Model-Based Explanation
No mystery loss, no missing power — just correct math, correct modeling, and fewer winter arguments.
🔗 https://shop.rf.guru/pages/why-the-y21-method-does-not-lose-6-db-a-clear-model-based-explanation

CMR vs CMRR vs Common-Mode Impedance
Three terms, one endless confusion. We untangle what actually matters when fighting noise — and what’s just marketing vocabulary.
🔗 https://shop.rf.guru/pages/cmr-vs-cmrr-vs-common-mode-impedance

Ferrite Mixes on HF – Chokes vs Broadband Transformers
Why the same ferrite behaves very differently depending on how you use it — and why winter QRO is unforgiving.
🔗 https://shop.rf.guru/pages/ferrite-mixes-on-hf-chokes-vs-broadband-transformers

What Recent Resistance Measurements Tell Us About the 20 m Carbon Whip
Cold weather, hard numbers, and uncomfortable conclusions for marketing brochures.
🔗 https://shop.rf.guru/pages/what-recent-resistance-measurements-tell-us-about-the-20-m-carbon-whip

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Practical RF Wisdom

Why dB Attenuation Specs on Ham Chokes Are a Mess
If the spec sheet looks impressive but explains nothing — this article explains why.
🔗 https://shop.rf.guru/pages/why-db-attenuation-specs-on-ham-chokes-are-a-mess

EIRP vs SWR – Why a 4:1 EFOC Beats a Perfect-Match EFHW
A winter reminder that radiated power matters more than what your tuner display says.
🔗 https://shop.rf.guru/pages/eirp-vs-swr-why-a-4-1-efoc-beats-a-perfect-match-efhw

Why Galvanic Decoupling at the Receiver Input Dramatically Improves HF SNR
Sometimes the biggest RX upgrade isn’t an antenna — it’s breaking the right ground loop.
🔗 https://shop.rf.guru/pages/why-galvanic-decoupling-at-the-receiver-input-dramatically-improves-hf-snr

How Antenna–Shack Decoupling Cuts Noise and Boosts HF Reception
Less current where it doesn’t belong means more signal where it does.
🔗 https://shop.rf.guru/pages/how-antenna-shack-decoupling-cuts-noise-and-boosts-hf-reception

Magloop Efficiency Myths – And What Really Determines Performance
Copper, current, and losses — not magic geometry — decide how well a magloop works.
🔗 https://shop.rf.guru/pages/magloop-efficiency-myths-and-what-really-determines-performance

Stop Chasing the Holy Grail Antenna
Because the perfect antenna doesn’t exist — but understanding does.
🔗 https://shop.rf.guru/pages/stop-chasing-the-holy-grail-antenna

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Debunking Myths

Stop Calling Your Choke “40 dB” – The Hidden Math They Never Tell You
If it sounds too clean to be true, it probably skipped the impedance calculation.
🔗 https://shop.rf.guru/pages/stop-calling-your-choke-40-db-the-hidden-math-they-never-tell-you

SWR Loss Is Largely a Myth – And Why Textbook Models Mislead Hams
A seasonal favorite: why reflected power isn’t the villain it’s made out to be.
🔗 https://shop.rf.guru/pages/swr-loss-is-largely-a-myth-and-why-textbook-models-mislead-hams

Why a Perfectly Symmetric Loop Often Isn’t — Especially When It’s Low
Snow-covered ground doesn’t care about your geometry assumptions.
🔗 https://shop.rf.guru/pages/why-a-perfectly-symmetric-loop-often-isn-t-especially-when-it-s-low

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RF Satire Corner

The Man with the Magical AI Detector
Because nothing says “science” like a black box and absolute confidence.
🔗 https://shop.rf.guru/pages/the-man-with-the-magical-ai-detector

The Cult of the Sacred Stubs
Shorted, open, quarter-wave, half-believed — gather round and adjust your coax.
🔗 https://shop.rf.guru/pages/the-cult-of-the-sacred-stubs

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YouTube Spotlight — Ham Florida Man

Reading done? Grab a coffee, lean back, and let Mark’s warm voice do the explaining. Our collaboration with Mark — K3ZD (“Ham Florida Man”) brings many of these RF topics to life on video, with clear explanations, real measurements, and zero myth-polishing.
🔗 Watch the featured videos from our collaboration

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As the year winds down, the bands fade in and out, the noise floor rises, and the same myths keep circulating — just with seasonal decorations. If this issue helps you question one claim, measure one assumption, or ignore one piece of bad advice, it has done its job.

Enjoy the holidays, keep experimenting, and remember: physics does not care about SWR, seasons, or marketing claims.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #10

Winter Is Coming: Expect Snow… and Someone Claiming SWR = Efficiency

 

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When the Snow Falls, the Myths Rise

The days are getting shorter, the coax is getting stiffer, and somewhere out there a ham is preparing to argue that his 1.0:1 SWR means his antenna is “near 100% efficient.” Winter does strange things to people.

As the cold sets in, the soldering irons glow brighter — and so do the inbox questions. This month turned into a blizzard of baluns, choking, real-world physics, and some delightful nonsense from the RF Satire Corner. Grab a hot drink, find a warm spot in the shack, and enjoy the newest batch of articles.

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Baluns & Real-World Choking

Why the Y21 Method Is the Only Ham Measurement That Actually Works
No more guesswork, no more “I feel like it’s working.” This is the gold standard for real choking measurements — and the only one that survives winter.
🔗 https://shop.rf.guru/pages/why-the-y21-method-is-the-only-ham-measurement-that-actually-works

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Deep Dives & Practical Physics

Why Your 9 dBd Collinear Might Be Losing to a 0 dBd Whip
Snow-covered roofs, coax geometry, and the brutal truth: gain on paper isn’t gain on air.
🔗 https://shop.rf.guru/pages/why-your-9-dbd-collinear-might-be-losing-to-a-0-dbd-whip

The Year the Robots Listened to the Ionosphere
AI that actually does something useful with HF — unlike certain comment-section experts.
🔗 https://shop.rf.guru/pages/the-year-the-robots-listened-to-the-ionosphere

The 1/4 Vertical Myth: If the Coax Runs Between Radials, It Can’t Bypass the Choke
Spoiler: yes it can. And it does. Winter just makes it easier to see the smoke.
🔗 https://shop.rf.guru/pages/1-4-vertical-myth-if-the-coax-runs-between-radials-it-can-t-bypass-the-choke

Understanding Near-Field and Far-Field for Antenna Performance
The difference between magic thinking and actual physics — now with diagrams.
🔗 https://shop.rf.guru/pages/understanding-near-field-and-far-field-for-antenna-performance

Quad-Core EFHW Inverted-L for 160/80/40 m
Why winter is the perfect torture test for real QRO hardware.
🔗 https://shop.rf.guru/pages/quad-core-efhw-inverted-l-160-m-80-m-40-m

Efficient Monoband EFHWs on 17–10 m
Short antennas done right — without fairy dust or magic capacitors.
🔗 https://shop.rf.guru/pages/efficient-monoband-efhws-on-17-10-m

Keeping Connectors Alive on Winter Farmland
Mud, moisture, manure — the triple threat. Here’s how to keep your hardware alive.
🔗 https://shop.rf.guru/pages/keeping-connectors-alive-on-winter-farmland

Carbon Whips vs Stainless Slider Whips on 10 m & 20 m
Cold weather reveals everything. Including efficiency myths.
🔗 https://shop.rf.guru/pages/carbon-fixed-size-whips-for-the-10m-20m-band-vs-stainless-slider-whip

The End-Fed That’s Never Really End-Fed
If it were truly end-fed, you’d need an infinite transformer. Physics laughs. We explain why.
🔗 https://shop.rf.guru/pages/the-end-fed-that-s-never-really-end-fed

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Debunking Myths

Half-Squares on 30–10 m: Feed Them at the Corner or Center — Not the End
Another episode of “but my friend on YouTube said…”
🔗 https://shop.rf.guru/pages/half-squares-on-30-10-m-feed-them-at-the-corner-or-center-not-the-end

Common Voltage vs Current Balun Myths Debunked
If winter had a flavor, it would be the taste of burned voltage baluns.
🔗 https://shop.rf.guru/pages/common-voltage-vs-current-balun-myths-debunked

Not Every HF Antenna Is a Compromise
Except the ones built by committees.
🔗 https://shop.rf.guru/pages/not-every-hf-antenna-is-a-compromise

The EFHW Capacitor – It’s Just a Shunt Capacitor, Nothing More
If this sentence upsets you… the article is definitely for you.
🔗 https://shop.rf.guru/pages/the-efhw-capacitor-it-s-just-a-shunt-capacitor-nothing-more

The EFHW Is a Dipole – But the EFOC Definitely Isn’t
Geometry doesn’t lie. Marketing often does.
🔗 https://shop.rf.guru/pages/the-efhw-is-a-dipole-but-the-efoc-definitely-isn-t

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RF Satire Corner

The Cult of the 4:1 Balun
Winter pilgrims gather… and everyone's SWR is exactly 2:1 for mysterious reasons.
🔗 https://shop.rf.guru/pages/the-cult-of-the-4-1-balun

The Gospel According to Professor Wattson – Part II
Now with 20% more sarcasm and 100% more “SWR salvation.”
🔗 https://shop.rf.guru/pages/the-gospel-according-to-professor-wattson-part-ii

The Etsy QRO Miracle: Five Ferrites to Rule Them All
This winter’s best fantasy novel — available in every questionable listing.
🔗 https://shop.rf.guru/pages/the-etsy-qro-miracle-five-ferrites-to-rule-them-all

You Won’t Believe How Lightweight and Efficient This Coax Is
Clickbait? Yes. True? Not even close.
🔗 https://shop.rf.guru/pages/you-won-t-believe-how-light-weight-and-efficient-this-coax-is

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Thanks for reading Issue #10 of the RF.Guru Lab Newsletter. Winter is here, the ionosphere is acting weird, the myths are breeding in the cold… and that means we have plenty more coming.

Stay warm, stay sharp, and remember: low SWR does not mean high efficiency — no matter how many times someone repeats it.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #9

Autumn Sparks: Baluns, Myths, and Mailbox Madness

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When Leaves Fall, Ideas Rise

The trees are shedding their leaves, field days are winding down, and over here the soldering iron is heating up again. Less outdoor noise means more writing — and our mailbox is buzzing. Many of your recent questions sparked full-blown articles, and some of them turned into myth-busting deep dives below.

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Baluns & Real-World Choking

Baluns in a Nutshell
A concise look at current vs voltage types — when to use which, and why the right choke placement matters more than the ferrite mix itself.
🔗 https://shop.rf.guru/pages/baluns-in-a-nutshell

How Much Choking Do You Really Need for RX and TX?
Forget the one-number dB myth. Here’s how to match common-mode impedance to your band and power level — without over-engineering it.
🔗 https://shop.rf.guru/pages/how-much-choking-do-you-really-need-for-rx-and-tx

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Deep Dives & Practical Physics

Why “Common-Mode” Is the Most Abused Term in Ham Radio
Engineers wince when this term gets tossed around. Let’s clean up the vocabulary — and your signal path.
🔗 https://shop.rf.guru/pages/why-common-mode-is-the-most-abused-term-in-ham-radio

When Open-Wire Feedline Starts to Radiate
That magic balanced line isn’t always innocent — we show when and why it radiates, and how to fix it.
🔗 https://shop.rf.guru/pages/when-open-wire-feedline-starts-to-radiate

Lowering SWR on a Dipole or Inverted-V by Making It Asymmetric
A touch of asymmetry can tame high SWR. Here’s the geometry trick that every tuner secretly loves.
🔗 https://shop.rf.guru/pages/lowering-swr-on-a-dipole-or-inverted-v-by-making-it-asymmetric

Stray Return Currents on the Coax Braid Can Accelerate Connector Corrosion
It’s not just electrochemistry — it’s RF. See how unseen common-mode current slowly eats your hardware.
🔗 https://shop.rf.guru/pages/stray-return-currents-on-the-coax-braid-can-accelerate-connector-corrosion

Drop SWR, Keep Return-Loss and Insertion-Loss
A fresh take on SWR obsession: lower numbers don’t always mean lower loss.
🔗 https://shop.rf.guru/pages/drop-swr-keep-return-loss-and-insertion-loss

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Debunking Myths

Licenses, Loopholes, and the Myth of “Real” Operators
Paper doesn’t make performance. A reflection on skill, ego, and the myth of the “full” license.
🔗 https://shop.rf.guru/pages/licenses-loopholes-and-the-myth-of-real-operators

Carbon Radiators – Miracle Antenna or Marketing Smoke?
If carbon really radiated well, your pencil would make a fine 20 m dipole. We’ll test the claims soon.
🔗 https://shop.rf.guru/pages/carbon-radiators-miracle-antenna-or-marketing-smoke

The 50-Ohm Myth – What Really Matters in Ladder-Line Baluns
Why chasing perfect 50 Ω can backfire, and how balanced systems behave in the real world.
🔗 https://shop.rf.guru/pages/the-50-ohm-myth-what-really-matters-in-ladder-line-baluns

Balanced vs Unbalanced Tuners
There’s no one-size-fits-all. Learn what “balanced” really means inside your tuner.
🔗 https://shop.rf.guru/pages/balanced-vs-unbalanced-tuners

Faraday Strips – 23 % of Nothing Is Still Nothing
The viral “miracle ground” myth gets a reality check with math and measurements.
🔗 https://shop.rf.guru/pages/faraday-strips-23-of-nothing-is-still-nothing

Why Most SWR Meters Don’t Really Measure SWR
Because what they show isn’t what you think it is. Here’s the calibration story behind the needle.
🔗 https://shop.rf.guru/pages/why-most-swr-meters-don-t-really-measure-swr

How Much Choking Do You Really Need for RX and TX?
(Yes, it’s that important.) A practical follow-up on measured common-mode impedance per band.
🔗 https://shop.rf.guru/pages/how-much-choking-do-you-really-need-for-rx-and-tx

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Errata & Modern Context

Kurt Speaks Out – Updated Technical Notes and Modern Errata
Classic truths revisited: which 1980s “laws” still hold, and which need an update for today’s rigs.
🔗 https://shop.rf.guru/pages/kurt-speaks-out-updated-technical-notes-and-modern-errata

Reflections Revisited – What’s Still True and What’s Been Refined Since W2DU
Half a century later, the reflection debate isn’t over. Here’s where measurement beats memory.
🔗 https://shop.rf.guru/pages/reflections-revisited-what-s-still-true-and-what-s-been-refined-since-w2du

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The Scientists Who Built RF

Thévenin Equivalents in Receive Systems
Why Thévenin’s 1883 insight still underpins every receiver front end today.
🔗 https://shop.rf.guru/pages/thevenin-equivalents-in-receive-systems

Johnson Noise & Thermal Noise – What Is It?
The random hiss that defines the ultimate sensitivity of your receiver.
🔗 https://shop.rf.guru/pages/johnson-noise-thermal-noise-what-is-it

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RF Satire Corner

The New Ham Species – Homo Ignoramicus Technicus
A gentle roast of the modern ham who fears ferrites and worships SWR dips.
🔗 https://shop.rf.guru/pages/the-new-ham-species-homo-ignoramicus-technicus

📻 The Gospel According to Professor Wattson
The fictional professor returns — this time preaching VSWR salvation to the un-tuned masses.
🔗 https://shop.rf.guru/pages/📻-the-gospel-according-to-professor-wattson

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Thanks for reading Issue #9 of the RF.Guru Lab Newsletter. Keep the questions coming — they’re fueling the next batch of experiments and myth demolitions.
Stay warm, stay curious, and as always — let physics do the talking.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

RF.Guru Incredible Lab Newsletter – Issue #8

Baluns, Beverages, and Beautifully Bad Ideas

 

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Fresh Technical Insights

What Is CESSB?
Controlled Envelope SSB isn’t new magic — it’s smarter modulation. Here’s how it squeezes more clean audio power from the same rig without splatter or smoke.
🔗 https://shop.rf.guru/pages/what-is-cessb

Transmatch Pi vs T vs L – Context Matters More Than Circuit
All tuners look good on paper. We break down when each topology shines — and why the “best” circuit depends more on feedline physics than schematic symbols.
🔗 https://shop.rf.guru/pages/transmatch-pi-vs-t-vs-l-context-matters-more-than-circuit

Silent Scout – Why a Passive Balanced ARDF Probe Beats LNA-On-Probe
Sometimes adding gain adds pain. Discover why passive, balanced ARDF probes outperform active ones when precision and null depth actually matter.
🔗 https://shop.rf.guru/pages/silent-scout-why-a-passive-balanced-ardf-probe-beats-lna-on-probe

EFHW 20 m–10 m – The Ground Sensitivity Problem
Short end-feds love to share current with your coax. We show how soil conductivity, height, and counterpoise length shape their real-world performance.
🔗 https://shop.rf.guru/pages/efhw-20m-10m-the-ground-sensitivity-problem

Why the 80 m Lazy Loop Needs a 4:1 Unun, Not a 4:1 Balun
Voltage-fed loops demand voltage transformers. Here’s why the humble 4:1 unun keeps them quiet and balanced, while a balun just invites common-mode chaos.
🔗 https://shop.rf.guru/pages/why-the-80-m-lazy-loop-needs-a-4-1-unun-not-a-4-1-balun

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Practical RF Wisdom

Why a Simple Choke on Your Mains Cable Isn’t Enough
One ferrite won’t save you. Learn how multi-stage suppression, cable routing, and proper grounding stop household noise before it hits your rig.
🔗 https://shop.rf.guru/pages/why-a-simple-choke-on-your-mains-cable-isn-t-enough

Antenna Impedance vs Transmission-Line Impedance
It’s not about 50 ohms perfection — it’s about understanding what really happens when they don’t match.
🔗 https://shop.rf.guru/pages/antenna-impedance-vs-transmission-line-impedance

Baluns in a Nutshell
A refresher on what baluns actually do, how to choose the right type, and why calling every transformer a “balun” still drives engineers mad.
🔗 https://shop.rf.guru/pages/baluns-in-a-nutshell

Making Sense of Antenna Analyzer Readings
Reactance, resistance, and resonance — demystified. Stop chasing dips and start reading what your analyzer is really telling you.
🔗 https://shop.rf.guru/pages/making-sense-of-antenna-analyzer-readings

Why Transients Matter More Than You Think in Ham Radio
Those tiny spikes during relay clicks and storms are silent killers. Here’s how to protect radios and tuners from invisible damage.
🔗 https://shop.rf.guru/pages/why-transients-matter-more-than-you-think-in-ham-radio

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Debunking Myths

Myth Buster – The EH Antenna
Physics still wins. We revisit measurements showing why this “revolutionary” design remains more heat than signal.
🔗 https://shop.rf.guru/pages/myth-buster-the-eh-antenna-physics-measurements-and-why-it-s-inefficient

Why Minimum Coax Length Matters for HF Antennas
No, it’s not voodoo — reflections, velocity factor, and impedance transformation make certain lengths truly useful.
🔗 https://shop.rf.guru/pages/why-minimum-coax-length-matters-for-hf-antennas

Why Voltage Transformers (UNUNs) Are More Efficient Than BALUNs for Real HF Antennas
Because most antennas aren’t perfectly balanced. Learn why UNUNs waste less and behave better in the real world.
🔗 https://shop.rf.guru/pages/why-voltage-transformers-ununs-are-more-efficient-than-baluns-for-real-hf-antennas

Why Ladder-Line Length Matters Between Tuner and Antenna
Feedline current distribution can make or break multi-band systems. Here’s the logic behind those “magic” lengths.
🔗 https://shop.rf.guru/pages/why-ladder-line-length-matters-between-tuner-and-antenna

Myth – The Double Bazooka Is a Magical Cure for Bad Antennas
It’s clever coax engineering, not a miracle. We show why performance rarely matches the legend.
🔗 https://shop.rf.guru/pages/myth-the-double-bazooka-is-a-magical-cure-for-bad-antennas

Myth Debunked – Loops Are Not Automatically Self-Balancing
Symmetry on paper doesn’t equal symmetry in current. Here’s how to actually balance your loop.
🔗 https://shop.rf.guru/pages/myth-debunked-loops-are-not-automatically-self-balancing

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RF Satire Corner

Over the Limit – Because Who Doesn’t Love a Smoldering PA
When “just a bit more drive” becomes a smoke test. A loving tribute to every operator who couldn’t stop at 100 W.
🔗 https://shop.rf.guru/pages/over-the-limit-because-who-doesn-t-love-a-smoldering-pa

The Legend of the HAREC Who Thought Antennas Die When Grounded
A mythical tale of theory gone hilariously wrong. Proof that exam answers and physics aren’t always best friends.
🔗 https://shop.rf.guru/pages/the-legend-of-the-harec-who-thought-antennas-die-when-grounded

RG-58 – The Spaghetti Cable of the Past
Thin, lossy, nostalgic. We salute the cable that taught generations of hams what not to use.
🔗 https://shop.rf.guru/pages/rg-58-the-spaghetti-cable-of-the-past

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Thanks for reading this edition of the RF.Guru Lab Newsletter. As always, we mix serious engineering with the occasional eyebrow raise — because in RF, the truth is often stranger than fiction.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #7

Untangling Coax, Myths, and the Occasional Burnt Finger

 

We realized a piece of content didn’t make it into the previous mail. Sorry about that! Here’s the proper version.

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Fresh Technical Insights

Why Toroid Choice Is More Than Just Permeability
Mix numbers aren’t the whole story. Core geometry, losses, and frequency behavior often matter more than that magic μ. Here’s how to pick a toroid that won’t betray you.
🔗 https://shop.rf.guru/pages/why-toroid-choice-is-more-than-just-permeability

The Future of Balun/Unun Modeling – A Peek Into New Research
Balun design is finally catching up with real-world data. This article explores new modeling methods that could change how we simulate and build wideband transformers.
🔗 https://shop.rf.guru/pages/the-future-of-balun-unun-modeling-a-peek-into-new-research

Hybrid Baluns vs. Chokes in End-Fed and Off-Center Antennas
Do you need a choke, a hybrid, or both? We dig into how each approach handles common-mode currents — and why “just one toroid” isn’t always enough.
🔗 https://shop.rf.guru/pages/hybrid-baluns-vs-chokes-in-end-fed-and-off-center-antennas

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Practical RF Wisdom

Waterproof RF Connectors Like a Pro – Cold Shrink vs. Self-Amalgamating Tape
Rain, UV, and time destroy coax connectors faster than SWR ever will. Here’s the real-world showdown between cold-shrink kits and the old tape-and-hope method.
🔗 https://shop.rf.guru/pages/waterproof-rf-connectors-like-a-pro-cold-shrink-vs-self-amalgamating-tape

NVIS, DX, and Local Reception – Understanding Polarization in HF
Verticals, dipoles, loops — they all interact differently with the ionosphere. Learn how polarization shapes your NVIS and DX results, and why it matters more than you think.
🔗 https://shop.rf.guru/pages/nvis-dx-and-local-reception-understanding-polarisation-in-hf

When the Sun Fires Twice – How Consecutive Flares Affect HF
Solar flares don’t always come alone. Back-to-back blasts can cripple HF propagation in surprising ways. Here’s what the science — and your radio — will tell you when it happens.
🔗 https://shop.rf.guru/pages/when-the-sun-fires-twice-how-consecutive-flares-affect-hf

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Debunking Myths

HF vs. GHz Circular Polarization – Myths, Limits, and Benefits
Circular polarization isn’t just for satellites. But myths abound when hams apply GHz logic to HF. This piece clears the fog.
🔗 https://shop.rf.guru/pages/hf-vs-ghz-circular-polarisation-myths-limits-and-benefits

The Ugly Balun – Why Are We Still Doing This?
PVC pipe, enamel wire, zip ties… sound familiar? We break down why the “ugly balun” refuses to die — and what actually works instead.
🔗 https://shop.rf.guru/pages/the-ugly-balun-why-are-we-still-doing-this

Hybrid Baluns vs. Chokes in End-Fed and Off-Center Antennas
Yes, it’s here again. Because this debate deserves both a technical deep dive and a myth-busting lens. Spoiler: hybrids and chokes aren’t interchangeable.
🔗 https://shop.rf.guru/pages/hybrid-baluns-vs-chokes-in-end-fed-and-off-center-antennas

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RF Satire Corner

SWR Derangement Syndrome
If 1.000:1 isn’t on the meter, the rig goes back in the box. A tongue-in-cheek look at those who worship the almighty SWR needle.
🔗 https://shop.rf.guru/pages/swr-derangement-syndrome

Height Is Might… Until Your Noise Floor Is King
That 30-meter mast might hear more switching supplies than signals. We roast the blind “higher is always better” mantra.
🔗 https://shop.rf.guru/pages/height-is-might-until-your-noise-floor-is-king

The Great Camper DX Famine – When Your Antenna’s Wideband Isn’t Wide Anything
Parking-lot field day, miracle antennas, and the sad truth about “wideband” sticks on RV roofs. Yes, we’re looking at you.
🔗 https://shop.rf.guru/pages/the-great-camper-dx-famine-when-your-antenna-s-wideband-isn-t-wide-anything

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Thanks for reading this edition of the RF.Guru Lab Newsletter. As always, we mix serious engineering with the occasional eyebrow raise — because in RF, the truth is often stranger than fiction.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

 

RF.Guru Incredible Lab Newsletter – Issue #6
Where RF theory meets reality — and occasionally laughs at it.

Fresh Technical Insights

Why Your Ferrite Might Be Cooking Alive
Spotlighting the thermal pitfalls of mismatched ferrite types—and how they can silently sabotage your gear.
https://shop.rf.guru/pages/why-your-ferrite-might-be-cooking-alive

The Illusion of Resonance: When Coax Becomes the Antenna
Sometimes your coax is radiating more than your antenna — and not in a good way. This piece explains how and why it happens, and how to detect and prevent it.
https://shop.rf.guru/pages/the-illusion-of-resonance-when-coax-becomes-the-antenna

Why the Wilkinson Divider Is a Superior Choice for Splitting RX Antennas
When splitting signals to multiple receivers, not all dividers are equal. Learn why the Wilkinson offers better isolation and balance in receive-only applications.
https://shop.rf.guru/pages/the-wilkinson-divider-is-a-superior-choice-for-splitting-rx-antennas

Practical RF Wisdom

Why Mixing Grounds Can Ruin Your Station
Floating shack? Multiple grounds? Here’s why improper bonding can cause noise, instability, or even safety hazards — and how to design a grounding scheme that works with your RF system instead of against it.
https://shop.rf.guru/pages/why-mixing-grounds-in-a-floating-shack-can-be-dangerous-and-how-to-do-it-right

Remote Tuners: Stop Installing Them at the Antenna Feedpoint
Remote tuners are often placed in the wrong spot. We explain why feedpoint placement is rarely optimal, how to position them for reduced loss, and when you actually should mount them at the antenna.
https://shop.rf.guru/pages/remote-tuners-stop-putting-them-where-you-don-t-need-them

The Coax Length Trick – When and Why It Works
Changing coax length can move the SWR dip, but it doesn’t “tune” the antenna. Here’s the science behind this trick, and when it’s actually useful for measurement or matching.
https://shop.rf.guru/pages/tuning-your-antenna-system-using-coax-cable-length

Debunking Myths

The SWR Myth: The Story of the "Lost" Power That Isn't Really Lost
Why mismatches don’t magically burn power, where losses really happen, and why antenna efficiency matters more than a perfect 1:1 match.
https://shop.rf.guru/pages/the-swr-myth-the-story-of-the-lost-power-that-isnt-really-lost

Why an LNA Won’t Fix Your Receiver’s Dynamic Range
Most LNAs won’t improve your receiver’s dynamic range — and can even make it worse — plus when and where they actually are essential.
https://shop.rf.guru/pages/why-an-lna-won-t-fix-your-receiver-s-dynamic-range

Reciprocity Is a Mathematical Theorem
Why real-world noise, feedline effects, and common-mode currents make RX antennas outperform TX/RX antennas — even though reciprocity still holds in theory.
https://shop.rf.guru/pages/reciprocity-is-a-mathematical-theorem

RF Satire Corner

The Sacred Faraday Blanket of Saint QRMbert
Because nothing says "noise suppression" like draping your shack in mythical cloth and hoping for the best. A lighthearted roast of the most bizarre EMC “solutions” we’ve encountered.
https://shop.rf.guru/pages/the-sacred-faraday-blanket-of-saint-qrmbert

Resonance Is Bliss – The Cult of the Perfect Match
SWR 1.000 forever! Even if your signal never leaves the backyard. We poke fun at the obsession with chasing a match at the expense of everything else that matters.
https://shop.rf.guru/pages/resonance-is-bliss-the-cult-of-the-perfect-match

Noise is the New DX – The Urban Operator’s Guide to Misguided RX
Still using your TX antenna to receive in the middle of an EMI jungle? Welcome to full-spectrum pain. Here’s why noise is not DX — and never was.
https://shop.rf.guru/pages/noise-is-the-new-dx-the-urban-operator-s-guide-to-misguided-rx

Community Spotlight

This month we highlight Mark — K3ZD (“Ham Florida Man” on YouTube). 

His videos cut through the myths with humor and solid RF knowledge — very much in line with what we do at RF.Guru.
https://www.youtube.com/watch?v=_01nmo6yP70

Thanks for reading this edition of the RF.Guru Lab Newsletter. As always, we mix serious engineering with the occasional eyebrow raise — because in RF, the truth is often stranger than fiction.

73,
Joeri – ON6URE
Founder – RF.Guru
https://rf.guru/

RF.Guru Incredible Lab Newsletter – Issue #5
Shocking Discoveries (Ground Not Included) — Where we separate signal from noise—literally.

Fresh Satirical Truth Bombs

The Cult of the Mirrored Bifilar Choke – Where Symmetry Goes to Die
https://shop.rf.guru/pages/the-cult-of-the-mirrored-bifilar-choke-where-symmetry-goes-to-die
Two wires wound together doesn’t automatically mean balance. In fact, it might just mean you’ve joined a cult of symmetry worship.

A Vertical Follows the Propagation
https://shop.rf.guru/pages/a-vertical-follows-the-propagation
No, your antenna doesn’t “follow” anything. This one takes aim at the pseudoscientific poetry infecting the hobby.

The Sacred Copper Rod – A Love Letter to the Most Useless Piece of Metal in Your Shack
https://shop.rf.guru/pages/the-sacred-copper-rod-a-love-letter-to-the-most-useless-piece-of-metal-in-your-shack
It’s shiny. It’s grounded. It’s… completely pointless for RF. But it feels right, doesn’t it?

HamRadio – The Faith-Based Wireless Religion
https://shop.rf.guru/pages/hamradio-the-faith-based-wireless-religion
From sacred SWR to miracle tuners, the religion of ham radio is alive and well — and desperately needs a reformation.

The Common Mode Conundrum – When Physics Meets Folklore
https://shop.rf.guru/pages/the-common-mode-conundrum-when-physics-meets-folklore
What really flows on your feedline may surprise you. Or terrify you. Especially if you believe in “clean” systems.

Deeper Technical Dives

Hidden Noise Machines – Understanding EMC in Everyday Electronics
https://shop.rf.guru/pages/hidden-noise-machines-understanding-emc-in-everyday-electronics
Your QRM probably isn’t from the neighbor’s solar panels. It might be inside your own shack.

Understanding Common Mode Buildup – And the Need for Multiple Chokes
https://shop.rf.guru/pages/understanding-common-mode-buildup-and-the-need-for-multiple-chokes
One choke is a wish. Two is a start. Here’s why common mode isn’t solved with a single ferrite and a prayer.

Non-Resonant TX Antennas in RX Mode – The Hidden Noise Problem
https://shop.rf.guru/pages/non-resonant-tx-antennas-in-rx-mode-the-hidden-noise-problem
Transmit antennas used for RX can silently ruin your noise floor — especially when they’re mismatched voltage collectors.

Understanding Near-Field, Far-Field, and RFI/EMC in Ham Radio (160m–2m)
https://shop.rf.guru/pages/understanding-near-field-far-field-and-rfi-emc-in-ham-radio-160m-2m
You can’t fix what you don’t understand. Know your fields. Know your enemy.

Short Radials and the Myth – Misreading Rudy Severns’ Work
https://shop.rf.guru/pages/short-radials-and-the-myth-misreading-rudy-severns-work
No, your 3-meter radials aren’t “almost as good.” Here’s what Rudy really said — and what the ham community chose to ignore.

Practical RF Wisdom

The Inductive Load – Why It’s the Convenient Radiator in RF Systems
https://shop.rf.guru/pages/the-inductive-load-why-it-s-the-convenient-radiator-in-rf-systems
Your tuner loves it. Your PA might not. Let’s decode the benefits and caveats of inductive loading in real-world antennas.

Physical Length vs Electrical Length – What’s the Difference?
https://shop.rf.guru/pages/physical-length-vs-electrical-length-whats-the-difference
They’re not the same, and thinking they are leads to design nightmares. Here’s how velocity factor really works.

The Truth About SWR, Resonance, and Efficient Radiation
https://shop.rf.guru/pages/the-truth-about-swr-resonance-and-efficient-radiation
A low SWR doesn’t mean efficient radiation. It just means less reflection at that point. Let’s stop pretending otherwise.

Antenna Tuners Don’t Tune Antennas – The Transmatch Misconception
https://shop.rf.guru/pages/antenna-tuners-dont-tune-antennas-the-transmatch-misconception
It tunes the system — not your antenna. And sometimes it tunes you into trouble.

The Open Wire Balanced Feedline – The Forgotten Ultra-Low-Loss Champion
https://shop.rf.guru/pages/the-open-wire-balanced-feedline-the-forgotten-ultra-low-loss-champion
It’s old school. It’s hard to route. But it’s unbeatable. Time to dust off the parallel wires.

Myth-Busting Debunkers

ARRL, K6WX & “Ground is a Myth” – But There’s Much, Much More to the Story
https://shop.rf.guru/pages/arrl-k6wx-ground-is-a-myth-but-theres-much-much-more-to-the-story
We agree on the surface. But here’s the nuance — and why safety and a return path for a current loop are not the same thing.

RX vs TX Grounding – Totally Different Games
https://shop.rf.guru/pages/rx-vs-tx-grounding-totally-different-games
A repeat? Yes. Because it’s that important. And still misunderstood.

Coaxial Cable – The Myth of Being Unbalanced
https://shop.rf.guru/pages/coaxial-cable-the-myth-of-being-unbalanced
The Cable That Carries Your Signal — And Your Problems

Why an LNA Won’t Fix Your Receiver’s Dynamic Range
https://shop.rf.guru/pages/why-an-lna-won-t-fix-your-receiver-s-dynamic-range
You can’t amplify your way into higher Dynamic Rage. You might just make the mess louder.

The Ham’s Obsession With Resonance
https://shop.rf.guru/pages/the-hams-obsession-with-resonance
It’s the holy grail that wasn’t. A 1:1 SWR does not mean everything’s okay — just that something isn’t bouncing back.

Have a question, spot an RF urban legend, or want to suggest a new topic?
Shoot me a message — every article starts with a curious OM asking "why?" and sometimes "oh why oh why ?"

73,
Joeri – ON6URE
Founder – RF.Guru
https://shop.rf.guru/pages/knowledge-base

RF.Guru Incredible Lab Newsletter – Issue #4
Where RF meets reality — and myths get politely (or not) obliterated.

Fresh Satirical Truth Bombs

Nectasy and the Myth of the Perfect Polar Plot
https://shop.rf.guru/pages/nectasy-and-the-myth-of-the-perfect-polar-plot
Think your NEC model makes you a better operator? Think again. This one’s for the pattern worshippers and polar plot prophets.

The Cult of Reciprocity™ – Why Your Antenna Doesn’t Care About You
https://shop.rf.guru/pages/the-cult-of-reciprocity%E2%84%A2-why-your-antenna-doesn-t-care-about-you
Turns out antennas are not sentient. They don’t know — or care — that you’re transmitting and not receiving. Reciprocity? Maybe. Relevance? You decide.

Deeper Technical Dives

The Truth About Low Noise Figures: Why MMICs Beat Low-NF Op-Amps in Real-World Antennas
https://shop.rf.guru/pages/the-truth-about-low-noise-figures-why-mmics-beat-low-nf-op-amps-in-real-world-antennas
Lab specs lie. Here’s why MMICs win in the noisy, ugly, real world of actual antennas — not spec sheets.

Why MMICs Behave as High Impedance Below Their Intended Frequency Range
https://shop.rf.guru/pages/why-mmics-behave-as-high-impedance-below-their-intended-frequency-range
A mystery solved. And no, it’s not magic — just RF physics.

RX vs TX Grounding: Totally Different Games
https://shop.rf.guru/pages/rx-vs-tx-grounding-totally-different-games
Ground loops, noise injection, and shielding gone wrong — learn why grounding for RX and TX isn't a one-size-fits-all story.

Practical RF Wisdom

The 5 Silent Killers of Your Power Amplifier — And How to Avoid Them
https://shop.rf.guru/pages/the-5-silent-killers-of-your-power-amplifier-and-how-to-avoid-them
If your amp could scream, it would. Here’s how to avoid turning your finals into toast.

The Perfect SWR of 2:1 on an Inductive Load — Or Not
https://shop.rf.guru/pages/the-perfect-swr-of-2-1-on-an-inductive-load-or-not
A great match to your tuner might still be a disaster at your PA. Here’s what SWR isn’t telling you.

Why Resonance Isn’t Always the SWR Sweet Spot
https://shop.rf.guru/pages/why-resonance-isn-t-always-the-swr-sweet-spot
That 1:1 may look pretty, but that doesn’t mean it’s working efficiently. Hint: look at X, not just SWR.

Myth-Busting Debunkers

Why “Wideband” EFHW Transformers Like the 49:1 Are Not Truly Wideband
https://shop.rf.guru/pages/why-wideband-efhw-transformers-like-the-49-1-are-not-truly-wideband
Spoiler: wideband in marketing, not in physics. EFHWs aren’t meant to be wideband — and here’s why that matters.

The Back-to-Back EFHW UNUN Transformer Measurement Myth
https://shop.rf.guru/pages/the-back-to-back-efhw-unun-transformer-measurement-myth
That clever-looking test setup? Completely wrong. Learn why back-to-back tests say more about your bench than your transformer.

ON6URE PotaSupreme™ Eats PotaPerformer for Breakfast
https://shop.rf.guru/pages/on6ure-potasupreme%E2%84%A2-eats-pota-performer-for-breakfast
Fun. Brutal. Accurate. This is where we put field mythology through the lab shredder — and the so-called “performer” doesn’t survive ;(

Have a question, spot an RF urban legend, or want to suggest a new topic?
Shoot me a message — every article starts with a curious OM asking "why?" and sometimes "oh why oh why ?"

73,
Joeri – ON6URE
Founder – RF.Guru
https://shop.rf.guru/pages/knowledge-base