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The Guru's Incredible Lab

RF.Guru · Engineering library

The Guru's Incredible Lab

One bench for the work scattered across antennas, ferrites, feedlines, EMC, receivers, measurement and the occasional beautifully bad idea.

607published engineering articles

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Origin storyWhy We Started RF.GuruThe reason the workshop exists: practical RF engineering, measured evidence and useful hardware.Open topic Why radio mattersA Modern Mission Statement for Amateur RadioA case for experimentation, technical literacy, shared infrastructure and building things that work.Open topic YouTube collaborationsHam Florida Man: Featured VideosBench work, field tests and RF conversations made together with fellow builders and operators.Open topic Dark humorSmoke & MirrorsBecause RF folklore, impossible specifications and heroic troubleshooting deserve their own corner.Open topic

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KCL, Reactance and Common-Mode Current: What the Coax Is Actually Doing

Did Heaviside Delete Maxwell? Scalar Waves and Longitudinal Fields

Do Receive-Antenna Revisions Make a Measurable Difference?

Does Antenna Reactance Create Common-Mode Current?

W8KHK Adds First-Hand Context to W2DU’s Laboratory History

Full-Wave Antennas: Geometry, Feedpoint and Pattern Decide

Inside RF.Guru 4:1 Ruthroff Transformers: Ratio, Balance and Power

RCA and Amateur Radio: From Marconi to Spacecraft Antennas

Coaxial Stub Isolation at 1.5 kW: Design, Measurement and Safety

Radio Noise Floor: Thermal Noise, Weather, RFI and Antenna Temperature

70 cm Repeater Desense: Isolation, Filtering and Site Tests

12.5 kHz Repeater Spacing: Coordination Beats Cavities

Reflected Power and Re-Reflection: Source, Load, Phase and Loss

Does Reflected Power Really Flow Back? Fields, Waves and Net Power

Soil Conductivity Maps: Inputs, Not RF Performance

SWR Measures Match—Not Gain, F/B or Efficiency

High-Angle Gain Does Not Guarantee an NVIS Path

EFHW Efficiency: Feedpoint Impedance, Matching and Return Current

Resonance, Match, SWR and Efficiency: Four Different Questions

Phased and Parasitic Arrays: Measure Currents, Loss and Pattern

NEC Antenna Models: What a Plot Predicts—and Cannot Prove

Capacitance Is Not Ground Loss: Where the Watts Actually Go

Elevated Radials: What N6LF Measured—and What He Did Not

Feedpoint Resistance: Why “R − 36 Ω” Is Not Ground Loss

Repeater Antennas: Specify the Site, Not the Market Label

Antenna Claims: Recognition Is Not Measurement

Why 180 dB Is a Repeater Coexistence Problem, Not Antenna Dynamic Range

The Tragedy of the Commons on 868 MHz

Licence-Free Does Not Mean Free to Use However You Like

When a 10% Duty-Cycle Mesh Hits Its Airtime Limit

Winlink at 144.850 MHz: Proposal, Band Plan and National Rules

Meshtastic and MeshCore in Europe: The Legal RF Framework

Quarter-Wave Fan Verticals: Match, Mutual Coupling and Pattern

A Gamma Match Is Still a Match

Meshtastic, MeshCore and CE Marking: The Hardware Trap

100 W at the Radio: Build the Complete Station Power Budget

RF Power in dB: Build an Honest HF Station Budget

5G Small Cell vs 1.5 kW HF: Why Watts Cannot Rank Exposure

Common-Mode Current: RF Safety at 100 W and QRO

Cosmic Rays, Solar Radio Blackouts and QRO HF Exposure

Repeater Antennas Above Roofs: Pattern, Clearance and Site Tests

How to Evaluate Antenna Claims: A Reproducible Evidence Checklist

RF Wattmeters: Where V²/50 Ends and Measurement Begins

What Makes a Bird Meter a Bird Meter? Power, SWR and Uncertainty

Reflected Power, SWR and Tuners: What the Finals Actually See

Radiation Efficiency Is Not Link Performance

Forward/Reflected Power and SWR: What the Meter Can Prove

Diversity Receive on HF: Why One Antenna Is Often Not Enough

HF Theory and Practice: Model the Whole RF System

A Ferrite Around Coax Measures Common-Mode Current, Not Shield Leakage

Ferrite Sleeves vs Wound Cores: Compare the Measured Choke

Where Should SWR Be Measured?

Clip-On Ferrites from HF to UHF: Part Data Before Folklore

Galvanic Isolation at HF: RF Transfer, Common Mode and Safety

DX Is Not Always Low Angle

The Transmission-Line Model Is Not the Whole Electromagnetic Reality

Ground Tuning Units: What an Artificial RF Ground Can—and Cannot—Do

Any Antenna Works. Efficiency Was the Question.

Morse, Vail and the Telegraph Code: A Documented History

Build the Station Around the Bottleneck

Receive Is Not Just Transmit in Reverse

Measuring an RF Power Budget: Forward, Reflected and Net Power

From First Questions to First QSOs: Engineering ON3VZ's HF Station

When Simple Pictures Fail

Antenna End Effect: Electrical Length, Matching and Return Paths

Resonance, Current and Radiated Power

Half-Square and Bobtail Curtain: Choosing the Feedpoint

Choosing an HF Antenna: Objectives, Site and Constraints

Stacked Hybrid 4:1 Baluns: Test the Assembly, Not the Label

Vertical Dipoles: Balance, Feedline Current and Ground Coupling

4:1 Baluns in the Real World: Transformation, Choking and Installation

When a Better Choke Makes the SWR Look Worse

Quarter-Wave Verticals Above Seawater: Counterpoise and Safety

Coax Return Current Is Not Common-Mode Current

Common-Mode Choke Test Jigs: Prove You Measured the DUT

50 Ω, 150 Ω and Real Common-Mode Choke Suppression

S21 Choke Measurements: When the Series Model Breaks

Outdoor RF Enclosures: IP Ratings, Condensation and Heat

RF UNUN Loss: From dB Claims to Measured Efficiency

Solar Inverter RFI: Diagnose the Installation, Not the Topology

Inverted-L Current Distribution: Where the Antenna Really Radiates

Vertical Antennas on Metal Roofs: Counterpoise, Pattern and Safety

Log-Periodic Antennas Over Metal Roofs: Broadband Is Not Immunity

Roy Lewallen’s Balun Paper: What the Experiments Actually Showed

Antenna Claims: How to Separate Match, Efficiency, Gain and Evidence

Meshtastic and MeshCore on EU 868 MHz: The Amateur-Radio Trap

Transmission-Line Loss vs Mismatch Loss: Where the Watts Go

Near-Resonant OCFD Antennas: Match Is Part of the System

Quarter-Wave vs 5/8-Wave Verticals: What Actually Changes

Vertical-Antenna Radials: Return Current, Ground Loss and Pattern

When Does a Second Antenna Tuner Help?

Michel Spelier Wins the World Again on 160 Metres

+1

Marine HF RFI: A Controlled Troubleshooting Case Study

Conjugate Match, 50 Ω and Distributed Networks

Conjugate Match, 50 Ω Match and Power Transfer

Shack Counterpoises: RF Return Paths Without Defeating Safety

Complete RF Current Paths: Differential Mode, Common Mode and Safety

Counterpoise, Ground Plane, Radials and Monopoles

Living Trees as HF Antennas: RF, Safety and Permission

OR7C/P Field Day 2026: Divide the Work, Keep the Station Predictable

Hans Schantz, UWB Thinking and the Limits of Ham-Radio Framing

When Entertainment Outruns Engineering

Bias-T Remote RF Switching at QRO: What Must Be Rated

Feedpoint or Remote Choke? Design the Current Path

Ground and Elevated Radials Together: Measure the Hybrid System

Rolling Up Coax: What Changes and What Does Not

Balanced Tuners, Differential Current and Common Mode

Automatic Coax Disconnects: One Layer, Not a Lightning-Protection System

Balun and Choke Ratings Under High SWR

Open-Wire Feeders, Balanced Tuners and Common-Mode Current

When 10 Meters Challenges a 40–10 m Off-Center-Fed Dipole

Do Antennas Attract Lightning? Geometry, Attachment and Risk

SWR, Feedline Loss and Radiated Power

EFHW Transformer Design and Qualification

tinySA Input Impedance: 50 Ohms, Attenuation, Overload and Spurs

SWR as a System Decision: Loss, Stress and Performance

The Legend of the Magic PL-259

GaN HF Amplifiers: What a 100 W Evaluation Board Does—and Does Not—Prove

The FCP on 80 Meters: When a Counterpoise Gets Mistaken for an Antenna

Choosing a Doublet Feedline Length by Measurement

Tools Every Ham Radio Operator Actually Needs

Beverage Antennas at the Beach: What Ground Conductivity Changes

SD-Antenna: Clever Compact HF Beamforming, but Not Magic

When 120 Radials Lose to an Inverted-L EFHW

Front, Back, and 0°: Why Phasing Still Needs a Convention

Stop Asking One Antenna to Cover 80–10 Metres

Characteristic Impedance Is Not a Resistor

John Portune’s Window-Line Argument Fails at the Foundation

Where to Measure a Multiband Antenna: Feedpoint or Shack?

Fixed 45°/90° Hybrids in a Receive 4-Square

9-Circle vs 4-Square on 160, 80 and 40 Meters

Beverage or BOG? Choose by Site, Pattern and Maintenance

Broadside in a Compact 4-Square: Useful, but Not the Main Event

Escaping SMPS Hell: Cleaning Hotspot Audio With a USB Filter

Why My Trusty Hytera Still Wins the Hotspot Test

The EFHW8010 Is Not a Broadband “Octave Antenna”

HF Station Lightning Protection: Why Partial Measures Can Fail

Why the “One Wire-Spacing” Rule for HF Window Line Is a Myth

Antenna Bonding and Protective Earth: Classify the Hazard First

Raised Vertical Height for Upper-HF DX: Model the Complete Installation

My TX Antenna Strategy from 160 Metres to 4 Metres

Low-Band EFHW Inverted-L: Match the Installed System

Mixed Ferrite Cores in One Coax Choke: What Actually Adds

Monoband EFHW L-Matching on 17 m, 15 m, 12 m and 10 m

Absolutes Stick. Nuance Dissolves.

Absolute stellingen blijven hangen. Nuance verdwijnt.

Les affirmations absolues s’ancrent. La nuance disparaît.

Resonance Isn’t Your Radiation Pattern

Resonance (X = 0) and Radiation Resistance Are Different Things

Resonance Isn’t Efficiency

Delta Loop vs Dipole Directionality

HF RF-Exposure Screening Distances: What a Table Can—and Cannot—Prove

Why “Best” Doesn’t Exist

PL-259/SO-239 at QRO: Power Is a System Rating

Coax at QRO: What High SWR Really Changes

Sevick’s Transmission Line Transformers, Re-Read

DL4ZAO’s “Balun-Workshop”: Where the Boundaries Matter

OS5Z “Dreamer” Antennas: Match, Pattern and Evidence

End-Fed vs Dipole RF Safety: Exposure, Contact and Arcing

LORAN: Why It Still Matters to Ham Radio

Going QRO? Measure Choke Current, Impedance and Heat

Top of the Bottom: Why 160 Meters Is “Top Band”

Broadband RF Transformers: Ratio, Ferrite, Loss and Power

FPGA Doesn’t Repeal Physics

+1

When “The Test” Becomes “The Truth”

Where SFDR Shines—and Where It Does Not

How to Read Transceiver “Lab Test Reports”

Ferrite Tolerances: Dimensions, AL, Impedance and RF Repeatability

Why S11 Alone Cannot Measure Antenna Efficiency

600 Ω Ladder Line With an Off-Centre-Fed Dipole

600 Ω Open-Wire Line: Balanced by Design, Tested in Place

“Unbalanced Antenna” Usually Means “Unbalanced to Ground”

Off-Center-Fed Dipole ≠ “Unbalanced Antenna”

Antenna Impedance vs Transmission-Line Impedance

Floating Ground: Electrical Safety vs RF Return Paths

It Depends—and That Is Where Engineering Starts

Het hangt ervan af.

Tout dépend du contexte

DC-Grounded Coax at HF: Why “Ground” Does Not Tame RF

Voltage and Current Travel Together on a 50 Ω Feed Line

How Long Is Too Long for an End-Fed Counterpoise?

Broadband HF Transformers: Topology, Flux and Honest Measurement

Magnetizing Reactance Is Not Common-Mode Isolation

Wire Antennas in a Small Garden

When Does the Feedline “Become the Antenna”?

The Phantom Third Conductor: Where Common-Mode Current Really Returns

Coax Unbalanced by Definition?

Why “Antenna Loss Calculators” Aren’t That Useful

Why UHF Hotspots Often Beat VHF in a Tiny Room

A Room Full of PIMs (Not the Cookies)

USB-C Charger Noise in RF Stations: Measure CM and DM Separately

Making AM Sound Better on an SDR

G3TXQ Common-Mode Chokes Revisited: What the Chart and Y21 Really Show

Good Enough Isn’t Good Enough Anymore

POTA PERformer, Challenger and Dominator: What the Numbers Prove

Polar Plot vs Picnic Table

A Portable Vertical Write-Up Starts as Engineering

The 96% SWR Myth: What 1.5:1 Actually Proves

NECtacy in the Park: When Model Precision Outruns Evidence

Counterpoise vs. Radials on HF: What’s the Difference

Two Radials and 4 dB of “Gain”: What Actually Changed?

Symmetrical “Ghost” Signals: IMD, I/Q Image or Overload?

Archaic by Design: The Beautiful Mess of Amateur Repeater Networks

RF Circulators and Isolators: What They Route—and What They Cannot Fix

1.5 kW Multi-2 Band-Pass Filters: What Five Poles Do—and Do Not Prove

Active E-Dipole Height: Ground, Noise, Pattern and Overload

One-Metre Active E-Probe Installation: Height, Reference and Overload

The 15 cm “Cheat Disk”: Wideband Linearity for an E-Probe

Receiver Test Tables: Stop Shopping by a Single Number

Antenna Gain Is Not a PIM Cure—But Lower Conducted Power Can Help

-153 dBc Low PIM: What the Number Means for Ham Radio

Your Active Antenna Isn’t the Upgrade ... This Is

Noise Isn’t “E or H” — It’s Coupling

House Noise Isn’t “Vertically Polarized”

Active Receive Antennas in the Attic: Win the Noise Fight First

+1

Commissioning an Active Receive Antenna

Is Japan on 80 Metres Real Low-Band DX?

Why the Contest Inverted-L Stayed Up After the Vertical Came Down

+1

EFHW Inverted-L or Ground Vertical? Compare the Complete Top-Band System

+1

Does an Inverted-L EFHW Have a “Direction”?

Receive Antennas in a Nutshell: Hear the World Again

+1

Dynamic Range Still Matters — Even with an Active Receive Antenna

Noise Figure for Active HF Receive Antennas: When It Matters

Small Active Receive Loops: Engineering Beats Brochures

+1

E-Field vs H-Field Receive Antennas for 0–30 MHz

+1

Does an Inverted-V Need a Feedpoint Choke?

Noise Coupled ≠ Noise Radiated

Why the PA0FRI “Coax Balun 1:4 and 1:1” Document Keeps Coming Back

Routing Coax for HF Antennas (1–30 MHz)

Why “I Don’t Want an SDR Ham Radio” Is a Technical Dead End

Common-Mode Current: Measure the Path Before You Choke It

EF-OCF vs EFHW for QRP: Make the Return Path Deliberate

+1

Low Feedpoint, Low Height: When a Terminated Antenna Is the Better Tool

+1

Why a Low EFHW Can “Look Good” on SWR

Your EFHW Isn’t Noisy — Your Feedline Is

Multiband Antenna Chokes: Measure Every Band

EFHW 80–10 and the “Space” Argument: Which Footprint Matters?

+1

LC Matching vs. EFHW Shunt Capacitors — Why These Are Not the Same Thing

The EFHW Shunt Capacitor: A Double-Edged Sword

Why Back-to-Back EFHW Measurements Keep Fooling People

Designing a 160/80 m EF-OCF: Flattop or Inverted-L?

+1

SWR Isn’t Obsolete — Worshipping It Is

Carbon Fiber vs Stainless Steel Telescopic Whips

QRO HF Antenna RF Exposure: What a Distance Can Prove

Outdoor Antenna Wire: Current, Voltage, Weather and Strain

Why “Resonant” Balanced Antennas Often Refuse to Tune

Why We Prefer One- or Two-Piece HF Aluminium Radiators

+1

Stop Chasing the “Holy Grail” Antenna

Small Transmitting Loops: Efficiency, Current and Capacitor Voltage

Carbon Radiators: What Does a Resistance Measurement Leave Open?

How Antenna–Shack Decoupling Cuts Noise and Boosts HF Reception

Receiver-Input Galvanic Isolation: When It Improves HF SNR

+1

HF Ferrite Selection: Chokes, Transformers and EFHW Limits

EIRP, Realized Gain and SWR: How to Compare EFHW and OCF Systems

Why We Use Two-Port Methods for Common-Mode Choke Measurements

Why dB Attenuation Specs on Ham Chokes Are a Mess

CMR vs CMRR vs Common-Mode Impedance

Why the Y21 Method Does NOT “Lose” 6 dB

When Hams Ask for More Enforcement: Law, Fees and Band Plans

EFOC29 on 80 Metres: Geometry, Matching and Current Boundaries

The VP2E Antenna: What It Is, How It Works, and How It Compares

HF Horizontal-U Wire: Why We Prefer EF-OCF Feeding Over EFHW

+1

End-Fed Antennas Still Need a Return Path

Transformer Turns Ratio: What It Changes—and What Sets Efficiency

9:1 Long-Wire vs EFHW/OCF: Compare the Complete System

+1

Why We Call an EF-OCF Near-Resonant and Multiband

+1

Carbon-Fibre vs Stainless HF Whips: What the Measurements Show

Keeping Connectors Alive on Winter Farmland

QRO HF Choke Placement: Measure the Current Path First

Monoband EFHW Matching on 17–10 m: Choose the Network From the Load

Quad-Core EFHW Inverted-Ls: Ratios, Loss and QRO Limits

20 m Verticals: EFHW or Quarter-Wave?

EF-OCF: When the Coax Exterior Is the Counterpoise

+1

COMPACtenna VHF/UHF: What the Patent and Tests Establish

Carbon-Fibre vs Stainless Antenna Elements: Loss, Joints and QRO

Understanding Near Field and Far Field for Antenna Performance

Mobile HF with Short Whips: Loading Coils vs. Tuners

Can Coax Between Radials Bypass a Common-Mode Choke?

Traveling-Wave Antennas and Common-Mode Noise: What Actually Helps

Trapped Radials or Separate Radials? Measure the Complete Vertical

When a Common-Mode Choke Makes an Antenna Worse

One FT-240 Core at QRO? Core Count Is Not a Rating

The Year the Robots Listened to the Ionosphere

Does Parallel-Wire Orientation Matter? Geometry, Current and Pattern

When a 9 dBd Collinear Loses to a 0 dBd Whip: Installed Gain and Coverage

Y21 Choke Measurement: Strengths, Limits and Alternatives

Measuring Common-Mode Chokes with the Y21 Method

Measuring Common-Mode Current: Why Coax Is Easier Than Open Wire

Drop SWR as a Verdict—Keep the Measurement

Coax-Connector Corrosion: Moisture, Galvanic Action and RF Stress

5/8-Wave Verticals: Matching, Ground, Pattern and Power

Can Asymmetry Lower SWR Without Losing the Antenna?

Stray Return Current on Coax: Why It Adds Loss, a Counterpoise Helps

EFHW Station Loss Budget: Coax, Transformer and Common Mode

Efficient Holiday & Fixed-Mobile HF Operation — The Hybrid Approach

Reflections Revisited: W2DU, W8KHK and Modern Measurement Boundaries

Your Transceiver Is Lying by Omission

Does Every Radio Need a Common-Mode Choke?

The Great BALUN / UNUN Confusion — Why the Labels Mislead

Why Perfect SWR Doesn’t Guarantee Clean Balance

When Open-Wire Feed Line Becomes Part of the Antenna

Why “Common Mode” Is the Most Abused Term in Ham Radio

Feeding a Resonant Dipole With 600 Ω Open-Wire

Passive ARDF Probes: Preserve the Null Before Adding Gain

Mains-Cable Ferrites: Common Mode, Differential Mode and Protective Earth

Pi, T or L Antenna Tuners: Choose by Load, Loss and Stress

EFHW on 20–10 m: The Ground-Sensitivity Problem

HF Current Baluns: Choose the Circuit, Not the Antenna Label

Why Coax Length Matters Less at VHF and Above—Except When It Does

What Is CESSB?

Making Sense of Antenna Analyzer Readings

80 m Lazy Loop: Why I Use a 4:1 UNUN and a Separate Choke

RG-58 Coax: When It Is Adequate and When Loss Wins

Why an EFHW Inverted-L Can Work Without a Radial Field

Why a Lower-Band Delta Loop Can Disappoint on Upper HF

A 160 m Inverted-V: Open-Wire Line, Coax and the Load Your Tuner Sees

Why a 49:1 EFHW Sweep Does Not Prove 80–10 Metre Performance

NVIS, DX and Local Reception: Understanding Polarisation in HF

Vehicle NVIS: Moving Whip or Parked Horizontal Antenna?

What the Giunzioni Team’s Low-Frequency Solver Means for Balun Modelling

When the Sun Fires Twice: How Consecutive Flares Affect HF

Solar Flares, Forecasting, and What It Means for Our Bands

Four-Square vs Half-Square: Compare the Complete Array

Why Quoting Wire Lengths in Ham Radio Is Misleading

Open vs Closed Antennas — Resonance vs Traveling Wave

What Common-Mode Really Means—and Why Hams Get It Wrong

Wat “Common Mode” werkelijk is en waarom we zo vaak op het verkeerde spoor zitten

Ce que signifie vraiment le mode commun — et pourquoi on se trompe souvent

Line Isolators: Place a Common-Mode Choke Where Current Flows

CCS, ICAS, PEP and Duty Cycle: How RF Power Ratings Should Be Stated

RF Noise in the Shack: Diagnose the Coupling Path Before Filtering

Common-Mode RF Current Control: Measure the Path, Then Place the Choke

Propagation from 2200 Metres to 2 Metres in Mid-Europe

Why Zero Reactance Matters When Tuning a TX Antenna

How Many Common-Mode Chokes? Let Measurements Decide

Why a Hexbeam Can Sound Louder Without a Choke

Remote Antenna Tuners: Put the Match Where It Matters

+1

Where Should the Antenna Resonance Dip Go?

Coax Length Transforms Impedance—It Does Not Tune the Antenna

+1

VSWR, Return Loss, S11 and S21: What Each Number Actually Means

What a 1:1 Common-Mode Choke Does—and Does Not Do

Windom and OCF Dipoles: Design the Return Path, Not Just the Ratio

+1

Five Ways an RF Power Amplifier Fails—and How to Prevent Them

The Perfect 2:1 SWR on an Inductive Load—or Not?

Active E-Field and H-Field Receive Antennas: What They Add Beside a Yagi

+2

Yagi Antennas: Common-Mode Listening Machines?

Antenna Height, Ground Loss and Resonance: Separate the Effects

Understanding Useful NVIS Receive Angles

Resonant ARDF Probes: When Tuning Helps—and When It Hurts

Non-Resonant HF Traps: When Broadband Current Shaping Helps

Measuring Antennas with a Field-Strength Meter

Antenna Gain vs Local Field Strength: What the Measurement Proves

Understanding Current Taper in Antennas

Why Polar Plots Lie—Unless the Model Earns Trust

Standing Waves on an Antenna Radiator: What They Show

Faraday Rotation: Why HF Polarization Refuses to Stay Put

Wideband HF Receiver Headroom: Filtering, Gain and Linearity

Dipoles and Doublets Above Seawater: What Lower Heights Change

HF Power Upgrades: When 500 W Is—and Isn’t—the Sweet Spot

Analog RF over Fibre vs Coax: Move the Noise Boundary

+1

Maxwell’s Equations — The RF Foundations You Forgot

LHCP/RHCP on Low-Band Field Day: Switch the Receive View

+1

Hotspot, Repeater PCB, Module or Complete Repeater?

Why 6 Metres Works on Almost Any Antenna

The Illusion of Resonance: Is the Coax Part of the Antenna?

The Illusion of Resonance: Match, Loading and Reality

High-Q vs Low-Q Antennas: Bandwidth, Efficiency and Evidence

Why Current and Voltage Distribution Define Antenna Behaviour

Halo and Small-Loop Transmit Antennas on HF

+1

Why a Band-Pass Filter Can Pass Its Test and the Station Still Fail

FT8 Can Hear Them — But Can You Work Them on SSB or CW?

Physical Length vs Electrical Length: Phase, Current and Pattern

One Wire to Rule the Waves? What a Saltwater Return Really Does

15 m or 20 m Mast for a 160/80 m Inverted-L?

+1

1:1 UNUN, Line Isolator or Choke? The Label Is Not the Circuit

50 Ω Coax: Matched Is Not “Balanced”

80 m Quarter-Wave Vertical or 160/80 m EFHW Inverted-L?

+1

80/40 m Inverted-L or Short Vertical? Compare the Installed System

A 20 m Tuned Vertical or a Low-Band EFHW Inverted-L?

+1

A 31 m Doublet on a 10 m Pole With Open-Wire Feedline

+1

A 44 m Doublet on a 16 m Pole With Open-Wire Feedline

A 49:1 EFHW Transformer Is Not Wideband Just Because It Tunes

A 51 m End-Fed Wire on 160 m: A Deployable Compromise

A Deep Null Is Not the Whole Receive Story

A Line Isolator Is More Than a dB Number

A VNA Trace on the Coax Shield Is Not the Whole Choke Test

ABS and Polycarbonate for High-Power RF Enclosures

Active Receive Antennas: Choose by Architecture and Site

Active Receiver Front Ends: Noise, Linearity and Overload

Active RX Antennas Near TX: Distance Is Not the Protection System

+1

Advanced Single-Stub Tuning Calculator

+1

Ampère-Maxwell Law in Toroids: Current, Flux and Choke Design

An 80 m-Long Doublet on a 16 m Pole With Open-Wire Feedline

An Asymmetric Inverted-V Is a Three-Conductor Problem

Antenna Current Distribution: Impedance, Pattern and Efficiency

Antenna Resonance Is Not Always the SWR Sweet Spot

+1

Antenna Tuners for End-Fed and Long Wires: What They Fix—and What They Cannot

Antenna-Tuner Baluns: Match the Function to the Current Path

ASA for Outdoor RF Structures: Material Is Only the Start

Autotransformer vs Ruthroff Transformer in UNUNs and BALUNs

+1

Balanced or Unbalanced Antenna Tuner? Test the Complete Interface

Balanced or Unbalanced Tuner? Follow the Load to the Antenna

Balcony-Mounted Verticals: Design the Whole Return Structure

Balun Functions: Voltage, Current, Transformation and Choking

Balun Types: Balance, Transformation and Common-Mode Control

Balun, UNUN and Line Isolator: Different Jobs, Sometimes the Same Hardware

Baluns in a Nutshell: Three Jobs, Not One Label

Bifilar vs. Coax: Which Winding Is Best for Chokes?

Camper HF Wire Antennas: Make the Installation Repeatable

Can One Wire Cover 160–10 m Efficiently?

Choosing a Ferrite Toroid: Permeability Is Only the Beginning

Choosing Between Near-Resonant and Non-Resonant End-Fed Wires

+1

Choosing Polycarbonate Enclosures for Outdoor RF Hardware

Coax Before the Choke: Define the EFHW Return Path

Coax Length, Tuner Range and the Reference Plane

+1

Coiled Into Compromise: What a Loading Coil Really Buys

Common-Mode Choke Measurements With a VNA: What the Trace Really Means

Common-Mode Choke Placement: Follow the Installed Current

Common-Mode Current in EFHW and Off-Centre-Fed Antennas

Common-Mode Noise in the Shack: Chokes, Bonding and Safety

Common-Mode Rejection and CMRR: From Device to Installed RF System

+1

Copper and Stainless Steel Bonding: PE, Lightning and RF

Counterpoise and Return Paths with 4:1 and 9:1 UNUNs

Current in Motion: How an Antenna Creates a Radio Wave

+1

Currents on the Coaxial Cable: A Multi-Lane Highway of RF Behavior

+1

DC-Grounded and DC-Open Antennas: What the Meter Does Not Tell You

+1

Designing Multiband Dipoles with Off-Resonance Traps

Diagnosing Outdoor HF Feed-System Failures

Dipole Feedpoint and Shack Chokes: Control the Intended Boundary

Do I Have Enough Baluns?

Do Tuners “Tune the Antenna”? Follow the Reference Plane

Do You Need a Kilowatt-Rated Balun at 100 Watts?

Does Feedline Length Matter?

EchoTracer3 — Technical Overview

EFHW Ground Lug: RF Return, Bonding and Safety Are Different Jobs

EFHW Return Current: Why “Voltage-Fed” Does Not Mean Loss-Free

EFHW Verticals for the Upper HF Bands

+1

EFHW, EF-OCF or End-Fed Long Wire: Which Fits Your Station?

Electrically Short RX Antennas Still Notice Nearby Objects

Elevated or On-Ground Radials? Follow the Installed Current

End-Fed Antennas Explained: Current Paths, Matching and Tradeoffs

End-Fed Antennas: Choke Impedance, Current and Placement

End-Fed SWR Measurement: Define the Return Path and Reference Plane

F1QM and ON6URE: The 10 m / 60 m NRT Decision

F4VUX's 160/80 m Inverted-L in the Ardennes

+1

Fan Vertical Mutual Coupling: The Tuning Trap

Faraday Strip Radials: 23% of What, Measured Where?

FD4 and Windom Antennas: Match the Current Path, Not the Name

+1

Feedpoint Geometry for Quarter-Wave and 5/8-Wave Verticals

Ferrite Core Retention: Adhesives, Tape, Clamps and Testing

Folded-Back Wire or a Final Cut?

Frequency Means in Off-Resonance Trap Design

From a Back-to-Back Trace to a Real EFHW Transformer Test

Gain Isn’t Everything: SNR in Receive Phased Arrays

+1

Galvanic Isolation on RX Lines: What a 1:1 Transformer Can—and Cannot—Do

Geometric-Mean Spacing for Multiband Receive Arrays

Ground-Mounted Vertical Lengths: Quarter-Wave, Half-Wave and Five-Eighths-Wave

Half-Square Feedpoints: Corner Current Feed or End Voltage Feed

Half-Wave Verticals Without a Ground Field

Half-Wavelength Coax Does Not Repair a Mismatch

High-Voltage Protection in UNUN and Balun Design

How Clay Soil Affects an HF Antenna

How Far from the House? Placing an Active Receive Antenna

+1

How Height Changes End-Fed Feedpoint Impedance

+1

How Much Choking Do You Really Need—for RX and TX?

Hybrid Baluns vs Separate Chokes: Follow the Current Path

Hybrid RF Transformers: Integration Is Not the Proof

If I Could Choose Only One QRO Multiband Antenna

Impedance and Matching: Follow the Whole RF Path

+1

Inductive Loads in RF Systems: Useful, but Not Radiators

+1

Inverted-L Clearance Near Metal, Buildings and Power Lines

Inverted-L Feedpoint Height: Follow the Whole Current Path

Inverted-L, Sloper or Flattop? Choose the Pattern, Not the Name

+1

Is a High-Radiation-Resistance TX Antenna Always a Good RX Antenna?

+1

Is Radiation Resistance as Important for RX Antennas as It Is for TX?

Is There a Minimum Coax Length for an HF Antenna?

+1

It All Starts With Lambda: Wavelength for Anyone

+1

Johnson–Nyquist Noise: The Receiver's Thermal Baseline

+1

Kurt Speaks Out: Transmission Lines, Chokes and Matching

+1

Ladder Line: The Almost-Utopian Feedline?

+1

Ladder-Line Length: Transform the Load, Don’t Worship a Number

+1

Licence Classes, Loopholes and the Myth of the “Real Operator”

Linked Dipole or 13 m Doublet? Compare the Whole 40–10 m System

Loop-on-Ground: Passive Transformer or Active Interface?

+1

Loops Are Not Automatically Self-Balancing

+1

Marine HF Antennas: Return Paths, Counterpoises and Safety

+2

Matching Networks and Efficiency: Where RF Power Goes

+1

Measure EFHW SWR and Resonance at the Right Reference Plane

+1

Modeling Antenna Patterns with Python: What the Model Can Prove

+1

Modeling Non-Resonant Traps in NEC: Measure the Network First

Monoband Antennas for DX: Choose the Pattern, Not the Label

Mounting Flanged RF Enclosures on Masts and Booms

Multiband Antennas Without a Radial Field

Multiband EFHW Transformers: Where Ferrite and Winding Loss Appear

Multiband Verticals and the 4:1 UNUN: Measure the Whole System

+1

Noise Figure: When It Matters and When It Doesn’t

+1

Not Every HF Antenna Is a Compromise: Define the Job First

NVIS Antenna Height: Design the Pattern for the Path

Off-Resonance Parallel-LC Trap Calculator

+1

ON6URE Visits SNW: A Mono-Output 80 m ARDF Receiver

ON6URE Visits UBA-TLS: SVXLink, Hotspots and Repeaters

Open-Wire Line, 4:1 Baluns and Tuners: Compare the Whole Feed System

ORA Field Day 2026: Two Stations, One Controlled RF Site

OT8M’s 160/80 m Inverted-L: What the Measurements Say

+1

Potting HF Transformers: When Encapsulation Helps or Hurts

Protective Coatings for Outdoor RF Electronics: Process Before Promises

QRP Z-Match vs AH-705 on a Doublet: Measure the Whole Feed System

Radio Weather: Kp, Solar Flux and the Path You Want

+1

Raised Radials or Raised Feedpoint? Two Different Upper-HF Changes

Receive-Array Phasing: Geometry, Calibration and Proof

Reciprocity Is a Mathematical Theorem

+1

Reducing Coupling in Quarter-Wave Fan Verticals

+1

Refer to RF.Guru

Repeaterverantwoordelijke: geen eretitel, maar een echte opdracht

RF in the Shack: Skin Effect, Exterior Current and Common Mode

+1

RG402 Common-Mode Chokes: Cable, Ferrite and Bend Limits

RX Chokes: Stop Thinking Only Like a Transmitter

RX vs TX Antennas: Same Physics, Different System Objectives

+1

Sailing-Vessel Antennas from HF to UHF

Short Radials and Rudy Severns: Read the Test Before the Rule

Six Feet of Radials Is Not a Universal Ground-System Rule

Skin Effect in Receive Antennas: Real Physics, Bounded Impact

Sleeve and Clip-On Ferrites at QRO: Measure the Finished Choke

Sloping a 160/80 m Inverted-L EFHW: What Really Changes?

Small-Space HF Wire Antennas: Choose the Constraint First

Solid-State Amplifiers, Multiband Wires and the Load a Tuner Must Handle

Stop Cutting Coax to “Fix” SWR

SWR, Reflected Power and Real Feed-Line Loss

T2LT Antenna: Where the Coax Stops Feeding and Starts Radiating

Tapped RF Autotransformers: Ratio, Return Path and Common Mode

The Counterpoise Is Part of the Antenna, Not an Optional Wire

+1

The Destructive Null: When Directionality Bites Back

The Double-Bazooka Dipole Is Not Antenna Medicine

The Doublet Is a Feed-System Decision, Not a Magic Length

The EFHW Capacitor Is a Shunt Branch—Inside a Complete Network

The EFLW37: A Practical 37-Metre End-Fed Wire

The EH Antenna: What Physics Predicts and Measurement Must Prove

The Guanella Transformer: Current Balun and UNUN Explained

+1

The History of RF Transformers: From Induction to Transmission-Line Networks

The Myth of the Random Wire Antenna

The Real Engineering Behind Motorized HF Antennas

The Ruthroff Transformer: Voltage Action, Balance and Common Mode

The Ugly Balun: Measure the Coax Choke Before You Mock It

+1

Thick Aluminium Tubes or Thin Wire?

Thunderstorm Safety for Amateur Radio: Disconnecting Is Only One Layer

+1

Thévenin Equivalents in Receive Systems

+1

Tinned-Copper Braid and Aluminium Masts: Build the Bond, Not the Myth

Trapped in a Trap: What Coaxial Traps Really Trade

Tuning a 160/80 m EFHW Inverted-L for SSB DX

+1

Tuning a Doublet: Match the Whole Feed System

Two Inverted-L End-Fed Wires for a 160/80/40 m Station

Type 316 Stainless Steel in Outdoor RF Hardware

Understanding Antenna Gain and Radiation Patterns

+1

Understanding Current Taper in Receive Antennas

+1

Understanding IP3: What It Is and What It Isn’t

Understanding Polarization: Why It Matters for Your Antennas

+1

Understanding the Null of a Shielded Active H-Field Loop

+1

UNUN or Current Balun? Let the Installed Load Decide

UNUN Types: Ratio, Topology and Common-Mode Control

Vergunningsvrij is niet regelvrij

Vertex-Fed Delta Loop or V-Dipole for Inter-European Paths?

+1

Vertical-Antenna Ground Systems: Radials, Earthing and Lightning

VertiCore 1/4th: The Reliable Workhorse for 15, 17, and 20 m

+1

VertiCore 5/8λ for 4, 6, 10 and 12 m

+1

VertiCore Monoband Series: 1/4λ and 5/8λ — Technical Overview

+1

VertX Fan Vertical: Why Matching Is Not Pattern Control

VertX Technical Architecture: Fewer Resonators, Better-Controlled Currents

VHF/UHF Hotspot and PCB Noise: A Hands-On EMC Investigation

Visible Enclosure Gaps: What Actually Determines the Seal

Wait—Aren’t Those the Same Antenna?

Weatherproofing Outdoor RF Connectors

What a 50-Ohm Load Can Tell You About a Ladder-Line Balun

What a “40 dB Choke” Number Actually Means

What an Inline SWR Meter Actually Measures

What Is the Biggest Effect of a Line Isolator?

What the Ground Lug Changes When a Transmit Antenna Receives

When a Dedicated Receive Antenna Helps

When an EFHW Capacitor Improves SWR, What Else Changed?

+1

When an External Antenna Tuner Helps a Short Wire

When Ferrite Runs Hot: Core Loss, Flux and Real Power Limits

When Is a Rotator Useful on an Active Magnetic Receive Loop?

+1

When Lowering an Inverted-L Feedpoint Barely Moves SWR

When Size Matters Less: Receive Antennas Below One-Twelfth Wavelength

+1

When the Better SWR Curve Lost the Field Test

Where the Current Flows, the Signal Grows

+1

Why 10 and 12 Metres Move When a Wire Becomes an Inverted-L

+1

Why a 6:1 UNUN Is Not Our Default for High-Power HF

Why a MMIC Can Look High-Impedance Below Its Intended Band

+1

Why a Perfectly Symmetric Loop Often Isn’t—Especially When It’s Low

+1

Why an Active Antenna Still Needs a High-Dynamic-Range Receiver

Why an LNA Won’t Fix Your Receiver’s Dynamic Range

Why Coax? The Practical and RF-Physics Advantages of Shielded Feedline

Why I Start With a 4:1 UNUN for Non-Harmonic Multiband Wires

Why IP68 Enclosures Can Still Develop Moisture Inside

Why I²R Matters: Where RF Current Becomes Heat

+1

Why Low-Band EFHW Installations Can Be Touchy

Why RF.Guru Uses a 4:1 UNUN and a Separate Choke

Why We Avoid Heavily Helical-Loaded 40 m Antennas

+1

Why We Designed EchoTracer3 Instead of Copying the MiniWhip

Why We Love Doublets—and When a G5RV Becomes a House of Cards

+1

Why We Stepped Back from the 80–10 m EFHW

Why We Still Use 600 Ω Open Wire—and When Window Line Is Better

Why We Use Simplified Antenna Models—and When We Use NEC

Wideband RF Phasing Networks: Materials, Balance and Calibration

Wilkinson Dividers for RX: Isolation, Loss and Alternatives

Wire Antennas on Sloped Terrain: Level, Follow the Ground or Aim the Pattern?

+1

Wire Length and Wavelength: Sloper, Flat-Top or Inverted-L?

+1

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