KCL, Reactance and Common-Mode Current: What the Coax Is Actually Doing
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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.
722published engineering articles
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Did Heaviside Delete Maxwell? Scalar Waves and Longitudinal Fields
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Will It Make Any Difference? How Our Receive Antennas Evolved
Read article ↗Does Antenna Reactance Create Common-Mode Current?
Read article ↗W2DU’s Son Read My Article—Then Corrected the Historical Record
Read article ↗Full-Wave Antennas Aren’t Bad
Read article ↗Inside RF.Guru 4:1 Ruthroff Transformers: Ratio, Balance and Power
Read article ↗RCA and Amateur Radio: From Marconi to Spacecraft Antennas
Read article ↗Coaxial Stub Isolation at 1.5 kW: Design, Measurement and Safety
Read article ↗Radio Noise Floor: Thermal Noise, Weather, RFI and Antenna Temperature
Read article ↗70 cm Repeater Desense: Isolation, Filtering and Site Tests
Read article ↗12.5 kHz Repeater Spacing: Coordination Beats Cavities
Read article ↗Reflected Power and Re-Reflection: Source, Load, Phase and Loss
Read article ↗Does Reflected Power Really Flow Back? Fields, Waves and Net Power
Read article ↗Soil Conductivity Maps: Inputs, Not RF Performance
Read article ↗SWR Cannot Validate Gain, F/B or Radiation Efficiency
Read article ↗High-Angle Radiation Is Not Automatically NVIS
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EFHW High Feedpoint Resistance Is Not Free Efficiency
Read article ↗Resonance, Match, SWR and Efficiency: Four Different Questions
Read article ↗PERformer Arrays: Cable Phase Is Not Element-Current Phase
Read article ↗A NEC Plot Is Not a Measurement: The KJ6ER Primer
Read article ↗Capacitance Does Not Burn Watts
Read article ↗Elevated Radials: What N6LF Measured—and What He Did Not
Read article ↗Feedpoint Resistance: Why “R − 36 Ω” Is Not Ground Loss
Read article ↗Repeater Antennas: Specify the Site, Not the Market Label
Read article ↗POTA PERformer: An Award Is Not an RF Certificate
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Why 180 dB Is a Repeater Coexistence Problem, Not Antenna Dynamic Range
Read article ↗The Tragedy of the Commons on 868 MHz
Read article ↗Licence-Free Does Not Mean Free to Use However You Like
Read article ↗When a 10% Duty-Cycle Mesh Hits Its Airtime Limit
Read article ↗Open Winlink for IARU Region 1: Coordinate, Then Build Open
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Meshtastic and MeshCore in Europe: The Legal RF Framework
Read article ↗Quarter-Wave Fan Verticals: Match, Mutual Coupling and Pattern
Read article ↗A Gamma Match Is Still a Match
Read article ↗Meshtastic, MeshCore and CE Marking: The Hardware Trap
Read article ↗100 W at the Radio: Build the Complete Station Power Budget
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RF Power in dB: Build an Honest HF Station Budget
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5G Small Cell vs 1.5 kW HF: Why Watts Cannot Rank Exposure
Read article ↗Common-Mode Current: RF Safety at 100 W and QRO
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Cosmic Rays, Solar Radio Blackouts and QRO HF Exposure
Read article ↗Is That Repeater Antenna Too Close to the Roof?
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WiMo’s Radials Guide: Where Useful Advice Becomes a Myth
Read article ↗RF Wattmeters: Where V²/50 Ends and Measurement Begins
Read article ↗What Makes a Bird Meter a Bird Meter? Power, SWR and Uncertainty
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Reflected Power, SWR and Tuners: What the Finals Actually See
Read article ↗The Very Efficient Antenna That Radiates to Nowhere
Read article ↗Forward/Reflected Power and SWR: What the Meter Can Prove
Read article ↗Diversity Receive on HF: Why One Antenna Is Often Not Enough
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HF Theory and Practice: Model the Whole RF System
Read article ↗A Ferrite Around Coax Measures Common-Mode Current, Not Shield Leakage
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Ferrite Sleeves vs Wound Cores: Compare the Measured Choke
Read article ↗Where Should SWR Be Measured?
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Clip-On Ferrites from HF to UHF: Part Data Before Folklore
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Galvanic Isolation at HF: RF Transfer, Common Mode and Safety
Read article ↗DX Is Not Always Low Angle
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The Transmission-Line Model Is Not the Whole Electromagnetic Reality
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Ground Tuning Units: What an Artificial RF Ground Can—and Cannot—Do
Read article ↗Any Antenna Works. Efficiency Was the Question.
Read article ↗Morse, Vail and the Telegraph Code: A Documented History
Read article ↗Stop Buying Radios. Start Building Stations.
Read article ↗Receive Is Not Just Transmit in Reverse
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The Great Watts Rip-Off: Right Diagnosis, Wrong Verdict?
Read article ↗From First Questions to First QSOs: Engineering ON3VZ's HF Station
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When Simple Pictures Fail
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Antenna End Effect: Electrical Length, Matching and Return Paths
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Resonance, Current and Radiated Power
Read article ↗Half-Square and Bobtail Curtain: Choosing the Feedpoint
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Choosing an HF Antenna: Objectives, Site and Constraints
Read article ↗Stacked Hybrid 4:1 Baluns: Test the Assembly, Not the Label
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Vertical Dipoles: Balance, Feedline Current and Ground Coupling
Read article ↗4:1 Baluns in the Real World: Transformation, Choking and Installation
Read article ↗When a Better Choke Makes the SWR Look Worse
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A Dual-Counterpoise Quarter-Wave Vertical Above Seawater
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Coax Return Current Is Not Common-Mode Current
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Common-Mode Choke Test Jigs: Prove You Measured the DUT
Read article ↗50 Ω, 150 Ω and Real Common-Mode Choke Suppression
Read article ↗S21 Choke Measurements: When the Series Model Breaks
Read article ↗Outdoor RF Enclosures: Why the Box Is Part of the Design
Read article ↗RF UNUN Loss: From dB Claims to Measured Efficiency
Read article ↗Solar Inverter RFI: Diagnose the Installation, Not the Topology
Read article ↗Inverted-L Current Distribution: Where the Antenna Really Radiates
Read article ↗Vertical Antennas on Metal Roofs: Counterpoise, Pattern and Safety
Read article ↗Log-Periodic Antennas Over Metal Roofs: Broadband Is Not Immunity
Read article ↗Roy Lewallen’s Balun Paper: What the Experiments Actually Showed
Read article ↗When Antenna Claims Outrun Antenna Physics
Read article ↗Meshtastic and MeshCore on EU 868 MHz: The Amateur-Radio Trap
Read article ↗Transmission-Line Loss vs Mismatch Loss: Where the Watts Go
Read article ↗Near-Resonant OCFD Antennas: Match Is Part of the System
Read article ↗Quarter-Wave vs 5/8-Wave Verticals: What Actually Changes
Read article ↗Vertical-Antenna Radials: Return Current, Ground Loss and Pattern
Read article ↗When Does a Second Antenna Tuner Help?
Read article ↗Michel Spelier Wins the World Again on 160 Metres
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+2
When Boat HF RFI Refuses to Behave: Jan’s Long Road to a Real Fix
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+1
Conjugate Match Is Real. “Matched Everywhere” Usually Isn’t.
Read article ↗Conjugate Match, 50 Ω Match and Power Transfer
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Shack Counterpoises: RF Return Paths Without Defeating Safety
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The Return Path Is Not the Other Hand
Read article ↗Counterpoise, Ground Plane, Radials and Monopoles
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Living Trees as HF Antennas: RF, Safety and Permission
Read article ↗OR7C/P Field Day 2026: Divide the Work, Keep the Station Predictable
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Hans Schantz, UWB Thinking and the Limits of Ham-Radio Framing
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When Entertainment Outruns Engineering
Read article ↗Bias-T Remote RF Switching at QRO: What Must Be Rated
Read article ↗Feedpoint or Remote Choke? Design the Current Path
Read article ↗Ground and Elevated Radials Together: Measure the Hybrid System
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Rolling Up Coax: What Changes and What Does Not
Read article ↗Balanced Tuners, Differential Current and Common Mode
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Automatic Coax Disconnects: One Layer, Not a Lightning-Protection System
Read article ↗Why Blanket High-SWR Balun Derating Rules Fall Apart
Read article ↗Open-Wire Feeders, Balanced Tuners and Common-Mode Current
Read article ↗When 10 Meters Challenges a 40–10 m Off-Center-Fed Dipole
Read article ↗Do Antennas Attract Lightning? Geometry, Attachment and Risk
Read article ↗SWR, Feedline Loss and Radiated Power
Read article ↗EFHW Transformer Design and Qualification
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tinySA Input Impedance: 50 Ohms, Attenuation, Overload and Spurs
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SWR as a System Decision: Loss, Stress and Performance
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The Legend of the Magic PL-259
Read article ↗GaN HF Amplifiers: What a 100 W Evaluation Board Does—and Does Not—Prove
Read article ↗The FCP on 80 Meters: When a Counterpoise Gets Mistaken for an Antenna
Read article ↗Choosing a Doublet Feedline Length by Measurement
Read article ↗Tools Every Ham Radio Operator Actually Needs
Read article ↗Beverage Antennas at the Beach: What Ground Conductivity Changes
Read article ↗SD-Antenna: Clever Compact HF Beamforming, but Not Magic
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When 120 Radials Lose to an Inverted-L EFHW
Read article ↗Front, Back, and 0°: Why Phasing Still Needs a Convention
Read article ↗Stop Asking One Antenna to Cover 80–10 Metres
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Characteristic Impedance Is Not a Resistor
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John Portune’s Window-Line Argument Fails at the Foundation
Read article ↗Where to Measure a Multiband Antenna: Feedpoint or Shack?
Read article ↗Fixed 45°/90° Hybrids in a Receive 4-Square
Read article ↗9-Circle vs 4-Square on 160, 80 and 40 Meters
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Beverage or BOG? Choose by Site, Pattern and Maintenance
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Broadside in a Compact 4-Square: Useful, but Not the Main Event
Read article ↗Escaping SMPS Hell: Cleaning Hotspot Audio With a USB Filter
Read article ↗Why My Trusty Hytera Still Wins the Hotspot Test
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The EFHW8010 Is Not a Broadband “Octave Antenna”
Read article ↗HF Station Lightning Protection: Why Partial Measures Can Fail
Read article ↗Why the “One Wire-Spacing” Rule for HF Window Line Is a Myth
Read article ↗Antenna Bonding and Protective Earth: Classify the Hazard First
Read article ↗Raised Vertical Height for Upper-HF DX: Model the Complete Installation
Read article ↗My TX Antenna Strategy from 160 Metres to 4 Metres
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Low-Band EFHW Inverted-L: Match the Installed System
Read article ↗Mixed Ferrite Cores in One Coax Choke: What Actually Adds
Read article ↗Monoband EFHW L-Matching on 17 m, 15 m, 12 m and 10 m
Read article ↗Absolutes Stick. Nuance Dissolves.
Read article ↗Absolute stellingen blijven hangen. Nuance verdwijnt.
Read article ↗Les affirmations absolues s’ancrent. La nuance disparaît.
Read article ↗Resonance Isn’t Your Radiation Pattern
Read article ↗Resonance (X = 0) and Radiation Resistance Are Different Things
Read article ↗Resonance Isn’t Efficiency
Read article ↗Delta Loop vs Dipole Directionality
Read article ↗HF RF-Exposure Screening Distances: What a Table Can—and Cannot—Prove
Read article ↗Why “Best” Doesn’t Exist
Read article ↗PL-259/SO-239 at QRO: Power Is a System Rating
Read article ↗Coax at QRO: What High SWR Really Changes
Read article ↗Sevick’s Transmission Line Transformers, Re-Read
Read article ↗DL4ZAO’s “Balun-Workshop”: Where the Boundaries Matter
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OS5Z “Dreamer” Antennas: Match, Pattern and Evidence
Read article ↗End-Fed vs Dipole RF Safety: Exposure, Contact and Arcing
Read article ↗LORAN: Why It Still Matters to Ham Radio
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Going QRO? Measure Choke Current, Impedance and Heat
Read article ↗Top of the Bottom: Why 160 Meters Is “Top Band”
Read article ↗Broadband RF Transformers: Ratio, Ferrite, Loss and Power
Read article ↗FPGA Doesn’t Repeal Physics
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+2
When “The Test” Becomes “The Truth”
Read article ↗Where SFDR Shines—and Where It Does Not
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How to Read Transceiver “Lab Test Reports”
Read article ↗Ferrite Tolerances: Dimensions, AL, Impedance and RF Repeatability
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Why S11 Alone Cannot Measure Antenna Efficiency
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600 Ω Ladder Line With an Off-Centre-Fed Dipole
Read article ↗600 Ω Open-Wire Line: Balanced by Design, Tested in Place
Read article ↗“Unbalanced Antenna” Usually Means “Unbalanced to Ground”
Read article ↗Off-Center-Fed Dipole ≠ “Unbalanced Antenna”
Read article ↗Antenna Impedance vs Transmission-Line Impedance
Read article ↗Floating Ground: Electrical Safety vs RF Return Paths
Read article ↗It Depends—and That Is Where Engineering Starts
Read article ↗Het hangt ervan af.
Read article ↗Tout dépend du contexte
Read article ↗DC-Grounded Coax at HF: Why “Ground” Does Not Tame RF
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Voltage and Current Travel Together on a 50 Ω Feed Line
Read article ↗How Long Is Too Long for an End-Fed Counterpoise?
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Broadband HF Transformers: Topology, Flux and Honest Measurement
Read article ↗Magnetizing Reactance Is Not Common-Mode Isolation
Read article ↗Wire Antennas in a Small Garden
Read article ↗When Does the Feedline “Become the Antenna”?
Read article ↗The Phantom Third Conductor: Where Common-Mode Current Really Returns
Read article ↗Coax Unbalanced by Definition?
Read article ↗Why “Antenna Loss Calculators” Aren’t That Useful
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Why UHF Hotspots Often Beat VHF in a Tiny Room
Read article ↗A Room Full of PIMs (Not the Cookies)
Read article ↗USB-C Charger Noise in RF Stations: Measure CM and DM Separately
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Making AM Sound Better on an SDR
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G3TXQ Common-Mode Chokes Revisited: What the Chart and Y21 Really Show
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Good Enough Isn’t Good Enough Anymore
Read article ↗POTA PERformer, Challenger and Dominator: What the Numbers Prove
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Polar Plot vs Picnic Table
Read article ↗A Portable Vertical Write-Up Starts as Engineering
Read article ↗The 96% SWR Myth: What 1.5:1 Actually Proves
Read article ↗NECtacy in the Park: When Model Precision Outruns Evidence
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Counterpoise vs. Radials on HF: What’s the Difference
Read article ↗Two Radials and 4 dB of “Gain”: What Actually Changed?
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Symmetrical “Ghost” Signals: IMD, I/Q Image or Overload?
Read article ↗Archaic by Design: The Beautiful Mess of Amateur Repeater Networks
Read article ↗RF Circulators and Isolators: What They Route—and What They Cannot Fix
Read article ↗1.5 kW Multi-2 Band-Pass Filters: What Five Poles Do—and Do Not Prove
Read article ↗Active E-Dipole Height: Ground, Noise, Pattern and Overload
Read article ↗One-Metre Active E-Probe Installation: Height, Reference and Overload
Read article ↗The 15 cm “Cheat Disk”: Wideband Linearity for an E-Probe
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Receiver Test Tables: Stop Shopping by a Single Number
Read article ↗Antenna Gain Is Not a PIM Cure—But Lower Conducted Power Can Help
Read article ↗-153 dBc Low PIM: What the Number Means for Ham Radio
Read article ↗Your Active Antenna Isn’t the Upgrade ... This Is
Read article ↗Noise Isn’t “E or H” — It’s Coupling
Read article ↗House Noise Isn’t “Vertically Polarized”
Read article ↗Active Receive Antennas in the Attic: Win the Noise Fight First
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Commissioning an Active Receive Antenna
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Is Japan on 80 Metres Real Low-Band DX?
Read article ↗Why the Contest Inverted-L Stayed Up After the Vertical Came Down
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+2
EFHW Inverted-L or Ground Vertical? Compare the Complete Top-Band System
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Does an Inverted-L EFHW Have a “Direction”?
Read article ↗Receive Antennas in a Nutshell: Hear the World Again
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Dynamic Range Still Matters — Even with an Active Receive Antenna
Read article ↗Noise Figure for Active HF Receive Antennas: When It Matters
Read article ↗Small Active Receive Loops: Engineering Beats Brochures
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E-Field vs H-Field Receive Antennas for 0–30 MHz
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Does an Inverted-V Need a Feedpoint Choke?
Read article ↗Noise Coupled ≠ Noise Radiated
Read article ↗Why the PA0FRI “Coax Balun 1:4 and 1:1” Document Keeps Coming Back
Read article ↗Routing Coax for HF Antennas (1–30 MHz)
Read article ↗Why “I Don’t Want an SDR Ham Radio” Is a Technical Dead End
Read article ↗Common-Mode Current: Measure the Path Before You Choke It
Read article ↗EF-OCF vs EFHW for QRP: Make the Return Path Deliberate
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Low Feedpoint, Low Height: When a Terminated Antenna Is the Better Tool
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Why a Low EFHW Can “Look Good” on SWR
Read article ↗Your EFHW Isn’t Noisy — Your Feedline Is
Read article ↗Multiband Antenna Chokes: Measure Every Band
Read article ↗EFHW 80–10 and the “Space” Argument: Which Footprint Matters?
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LC Matching vs. EFHW Shunt Capacitors — Why These Are Not the Same Thing
Read article ↗The EFHW Shunt Capacitor: A Double-Edged Sword
Read article ↗Why Back-to-Back EFHW Measurements Keep Fooling People
Read article ↗160/80 m EF-OCF or EFHW: Which Fits the Site?
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+3
SWR Isn’t Obsolete — Worshipping It Is
Read article ↗Carbon Fiber vs Stainless Steel Telescopic Whips
Read article ↗QRO HF Antenna RF Exposure: What a Distance Can Prove
Read article ↗Outdoor Antenna Wire: Current, Voltage, Weather and Strain
Read article ↗Why “Resonant” Balanced Antennas Often Refuse to Tune
Read article ↗Why We Prefer One- or Two-Piece HF Aluminium Radiators
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Stop Chasing the “Holy Grail” Antenna
Read article ↗MagLoop Efficiency Myths: Why the 40/80 m Shortcut Fails
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Carbon Radiators: What Does a Resistance Measurement Leave Open?
Read article ↗How Antenna–Shack Decoupling Cuts Noise and Boosts HF Reception
Read article ↗Receiver-Input Galvanic Isolation: When It Improves HF SNR
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HF Ferrite Selection: Chokes, Transformers and EFHW Limits
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EIRP vs SWR: Why I Prefer the 4:1 EFOC Trade-Off
Read article ↗Why We Use Two-Port Methods for Common-Mode Choke Measurements
Read article ↗Why dB Attenuation Specs on Ham Chokes Are a Mess
Read article ↗CMR vs CMRR vs Common-Mode Impedance
Read article ↗Why the Y21 Method Does NOT “Lose” 6 dB
Read article ↗When Hams Ask for More Enforcement: Law, Fees and Band Plans
Read article ↗EFOC29 on 80 Metres: Geometry, Matching and Current Boundaries
Read article ↗The VP2E Antenna: What It Is, How It Works, and How It Compares
Read article ↗HF Horizontal-U Wire: Why We Prefer EF-OCF Feeding Over EFHW
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End-Fed Antennas Still Need a Return Path
Read article ↗Transformer Turns Ratio: What It Changes—and What Sets Efficiency
Read article ↗9:1 Long-Wire vs EFHW/OCF: Compare the Complete System
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Why We Call an EF-OCF Near-Resonant and Multiband
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+2
Carbon or Stainless HF Whips: What Are We Trading?
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Keeping Connectors Alive on Winter Farmland
Read article ↗QRO HF Choke Placement: Measure the Current Path First
Read article ↗Monoband EFHW Matching on 17–10 m: Choose the Network From the Load
Read article ↗Quad-Core EFHW Inverted-Ls: Ratios, Loss and QRO Limits
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20 m Verticals: EFHW or Quarter-Wave?
Read article ↗EF-OCF: Why I Put the Coax Exterior to Work
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+2
COMPACtenna VHF/UHF: What the Patent and Tests Establish
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Carbon-Fibre vs Stainless Antenna Elements: Loss, Joints and QRO
Read article ↗Understanding Near Field and Far Field for Antenna Performance
Read article ↗Mobile HF with Short Whips: Loading Coils vs. Tuners
Read article ↗Can Coax Between Radials Bypass a Common-Mode Choke?
Read article ↗Traveling-Wave Antennas and Common-Mode Noise: What Actually Helps
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Trapped Radials or Separate Radials? Measure the Complete Vertical
Read article ↗When a Common-Mode Choke Makes an Antenna Worse
Read article ↗One FT-240 Core at QRO? Core Count Is Not a Rating
Read article ↗The Year the Robots Listened to the Ionosphere
Read article ↗Does Parallel-Wire Orientation Matter? Geometry, Current and Pattern
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+1
When a 9 dBd Collinear Loses to a 0 dBd Whip: Installed Gain and Coverage
Read article ↗Y21 Choke Measurement: Strengths, Limits and Alternatives
Read article ↗Measuring Common-Mode Chokes with the Y21 Method
Read article ↗Measuring Common-Mode Current: Why Coax Is Easier Than Open Wire
Read article ↗Drop SWR as a Verdict—Keep the Measurement
Read article ↗Coax-Connector Corrosion: Moisture, Galvanic Action and RF Stress
Read article ↗5/8-Wave Verticals: Matching, Ground, Pattern and Power
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+1
Can Asymmetry Lower SWR Without Losing the Antenna?
Read article ↗Stray Return Current on Coax: Why It Adds Loss, a Counterpoise Helps
Read article ↗Stop Blaming Your Coax Before Checking the EFHW
Read article ↗Efficient Holiday & Fixed-Mobile HF Operation — The Hybrid Approach
Read article ↗Reflections Revisited: W2DU, W8KHK and Modern Measurement Boundaries
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+1
Your Transceiver Is Lying by Omission
Read article ↗Does Every Radio Need a Common-Mode Choke?
Read article ↗The Great BALUN / UNUN Confusion — Why the Labels Mislead
Read article ↗Why Perfect SWR Doesn’t Guarantee Clean Balance
Read article ↗When Open-Wire Feed Line Becomes Part of the Antenna
Read article ↗Why “Common Mode” Is the Most Abused Term in Ham Radio
Read article ↗Feeding a Resonant Dipole With 600 Ω Open-Wire
Read article ↗Passive ARDF Probes: Preserve the Null Before Adding Gain
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+1
Mains-Cable Ferrites: Common Mode, Differential Mode and Protective Earth
Read article ↗Is the Pi Network Obsolete? Pi, T and L in Context
Read article ↗EFHW on 20–10 m: The Ground-Sensitivity Problem
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+1
HF Baluns: Why I Usually Separate Matching and Choking
Read article ↗Why Coax Length Matters Less at VHF and Above—Except When It Does
Read article ↗What Is CESSB?
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+1
Making Sense of Antenna Analyzer Readings
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+1
80 m Lazy Loop: Why I Use a 4:1 UNUN and a Separate Choke
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+1
RG-58 Coax: When It Is Adequate and When Loss Wins
Read article ↗Why an EFHW Inverted-L Can Work Without a Radial Field
Read article ↗Why a Lower-Band Delta Loop Can Disappoint on Upper HF
Read article ↗A 160 m Inverted-V: Open-Wire Line, Coax and the Load Your Tuner Sees
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+1
Why a 49:1 EFHW Sweep Does Not Prove 80–10 Metre Performance
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+1
NVIS, DX and Local Reception: Understanding Polarisation in HF
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+1
Vehicle NVIS: Moving Whip or Parked Horizontal Antenna?
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+1
What the Giunzioni Team’s Low-Frequency Solver Means for Balun Modelling
Read article ↗When the Sun Fires Twice: How Consecutive Flares Affect HF
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+1
Solar Flares, Forecasting, and What It Means for Our Bands
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+1
Four-Square vs Half-Square: Compare the Complete Array
Read article ↗Why Quoting Wire Lengths in Ham Radio Is Misleading
Read article ↗Open vs Closed Antennas — Resonance vs Traveling Wave
Read article ↗What Common-Mode Really Means—and Why Hams Get It Wrong
Read article ↗Wat “Common Mode” werkelijk is en waarom we zo vaak op het verkeerde spoor zitten
Read article ↗Ce que signifie vraiment le mode commun — et pourquoi on se trompe souvent
Read article ↗Line Isolators: Place a Common-Mode Choke Where Current Flows
Read article ↗CCS, ICAS, PEP and Duty Cycle: How RF Power Ratings Should Be Stated
Read article ↗RF Noise in the Shack: Diagnose the Coupling Path Before Filtering
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+1
Common-Mode RF Current Control: Measure the Path, Then Place the Choke
Read article ↗Propagation from 2200 Metres to 2 Metres in Mid-Europe
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+1
Why Zero Reactance Matters When Tuning a TX Antenna
Read article ↗How Many Common-Mode Chokes? Let Measurements Decide
Read article ↗More Hexbeam Power Without a Choke? Think Again.
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+1
Remote Antenna Tuners: Put the Match Where It Matters
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+2
Where Should the Antenna Resonance Dip Go?
Read article ↗Coax Length Transforms Impedance—It Does Not Tune the Antenna
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+2
VSWR, Return Loss, S11 and S21: What Each Number Actually Means
Read article ↗What a 1:1 Common-Mode Choke Does—and Does Not Do
Read article ↗Windom and OCF Dipoles: Design the Return Path, Not Just the Ratio
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+2
Five Ways an RF Power Amplifier Fails—and How to Prevent Them
Read article ↗The Perfect 2:1 SWR on an Inductive Load—or Not?
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+1
Active E-Field and H-Field Receive Antennas: What They Add Beside a Yagi
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+3
Yagi Antennas: Common-Mode Listening Machines?
Read article ↗Antenna Height, Ground Loss and Resonance: Separate the Effects
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+1
Understanding Useful NVIS Receive Angles
Read article ↗Resonant ARDF Probes: When Tuning Helps—and When It Hurts
Read article ↗Non-Resonant HF Traps: When Broadband Current Shaping Helps
Read article ↗
+1
Measuring Antennas with a Field-Strength Meter
Read article ↗Antenna Gain vs Local Field Strength: What the Measurement Proves
Read article ↗Understanding Current Taper in Antennas
Read article ↗Why Polar Plots Lie—Unless the Model Earns Trust
Read article ↗Standing Waves on an Antenna Radiator: What They Show
Read article ↗
+1
Faraday Rotation: Why HF Polarization Refuses to Stay Put
Read article ↗
+1
Wideband HF Receiver Headroom: Filtering, Gain and Linearity
Read article ↗Dipoles and Doublets Above Seawater: What Lower Heights Change
Read article ↗
+1
HF Power Upgrades: When 500 W Is—and Isn’t—the Sweet Spot
Read article ↗Analog RF over Fibre vs Coax: Move the Noise Boundary
Read article ↗
+2
Maxwell’s Equations — The RF Foundations You Forgot
Read article ↗LHCP/RHCP on Low-Band Field Day: Switch the Receive View
Read article ↗
+2
Hotspot, Repeater PCB, Module or Complete Repeater?
Read article ↗Why 6 Metres Works on Almost Any Antenna
Read article ↗
+1
The Illusion of Resonance: Is the Coax Part of the Antenna?
Read article ↗
+1
The Illusion of Resonance: Match, Loading and Reality
Read article ↗
+1
High-Q vs Low-Q Antennas: Bandwidth, Efficiency and Evidence
Read article ↗Why Current and Voltage Distribution Define Antenna Behaviour
Read article ↗
+1
Halo and Small-Loop Transmit Antennas on HF
Read article ↗
+2
Why a Band-Pass Filter Can Pass Its Test and the Station Still Fail
Read article ↗FT8 Can Hear Them — But Can You Work Them on SSB or CW?
Read article ↗
+1
Physical Length vs Electrical Length: Phase, Current and Pattern
Read article ↗One Wire to Rule the Waves? What a Saltwater Return Really Does
Read article ↗15 m or 20 m Mast for a 160/80 m Inverted-L?
Read article ↗
+2
1:1 UNUN, Line Isolator or Choke? The Label Is Not the Circuit
Read article ↗50 Ω Coax: Matched Is Not “Balanced”
Read article ↗80 m Quarter-Wave Vertical or 160/80 m EFHW Inverted-L?
Read article ↗
+2
80/40 m Inverted-L or Short Vertical? Compare the Installed System
Read article ↗
+1
A 20 m Tuned Vertical or a Low-Band EFHW Inverted-L?
Read article ↗
+2
A 31 m Doublet on a 10 m Pole With Open-Wire Feedline
Read article ↗
+2
A 44 m Doublet on a 16 m Pole With Open-Wire Feedline
Read article ↗
+1
A 49:1 EFHW Transformer Is Not Wideband Just Because It Tunes
Read article ↗A 51 m End-Fed Wire on 160 m: A Deployable Compromise
Read article ↗
+1
A Deep Null Is Not the Whole Receive Story
Read article ↗A Line Isolator Is More Than a dB Number
Read article ↗
+1
A Quiet Receiver Is Not a Current Probe
Read article ↗
+1
A Stainless-Steel Stake Is an Installed Impedance
Read article ↗
+2
A VNA Trace on the Coax Shield Is Not the Whole Choke Test
Read article ↗A “Floating Shack” Stops Floating When Another Cable Enters
Read article ↗
+3
ABS and Polycarbonate for High-Power RF Enclosures
Read article ↗Active MMIC or Passive Transformer Phasing for RX Arrays?
Read article ↗
+2
Active Receive Antennas: Choose by Architecture and Site
Read article ↗
+1
Active Receiver Front Ends: Noise, Linearity and Overload
Read article ↗
+1
Active RX Antennas Near TX: Distance Is Not the Protection System
Read article ↗
+2
Advanced Single-Stub Tuning Calculator
Read article ↗
+2
After a Surge: Can You Still Trust the Coaxial Protector?
Read article ↗
+3
Ampère-Maxwell Law in Toroids: Current, Flux and Choke Design
Read article ↗
+1
An 80 m-Long Doublet on a 16 m Pole With Open-Wire Feedline
Read article ↗
+1
An Asymmetric Inverted-V Is a Three-Conductor Problem
Read article ↗
+1
Antenna Current Distribution: Impedance, Pattern and Efficiency
Read article ↗
+1
Antenna Resonance Is Not Always the SWR Sweet Spot
Read article ↗
+2
Antenna Tuners Are Not Cheating: What a Transmatch Actually Does
Read article ↗
+1
Antenna Tuners for End-Fed and Long Wires: What They Fix—and What They Cannot
Read article ↗
+1
Antenna-Tuner Baluns: Match the Function to the Current Path
Read article ↗ASA for Outdoor RF Structures: Material Is Only the Start
Read article ↗Autotransformer vs Ruthroff Transformer in UNUNs and BALUNs
Read article ↗
+2
Balanced or Unbalanced Antenna Tuner? Test the Complete Interface
Read article ↗Balanced or Unbalanced Tuner? Follow the Load to the Antenna
Read article ↗
+1
Balcony-Mounted Verticals: Design the Whole Return Structure
Read article ↗
+1
Balun Functions: Voltage, Current, Transformation and Choking
Read article ↗
+1
Balun Types: Balance, Transformation and Common-Mode Control
Read article ↗
+1
Balun, UNUN and Line Isolator: Different Jobs, Sometimes the Same Hardware
Read article ↗Baluns in a Nutshell: Three Jobs, Not One Label
Read article ↗
+1
Bifilar vs. Coax: Which Winding Is Best for Chokes?
Read article ↗Can a 20 m Vertical Beat a Yagi? Compare the Installed Pattern
Read article ↗
+1
Can One Wire Cover 160–10 m or 80–10 m Efficiently?
Read article ↗
+1
Choosing a Ferrite Toroid: Permeability Is Only the Beginning
Read article ↗
+1
Choosing Between Near-Resonant and Non-Resonant End-Fed Wires
Read article ↗
+2
Choosing PTFE-Insulated Tinned Stranded Copper for RF Windings
Read article ↗
+1
Coax Before the Choke: Define the EFHW Return Path
Read article ↗
+1
Coax Length, Tuner Range and the Reference Plane
Read article ↗
+2
Coax or Balanced Feed Line? Choose the Complete System
Read article ↗
+1
Coax-to-Earth Clamps: When Bonding Moves the Choke Boundary
Read article ↗
+2
Coiled Into Compromise: What a Loading Coil Really Buys
Read article ↗
+1
Common-Mode Buildup: When Multiple Chokes Help
Read article ↗
+1
Common-Mode Choke Measurements With a VNA: What the Trace Really Means
Read article ↗Common-Mode Choke Placement: Follow the Installed Current
Read article ↗
+1
Common-Mode Current in EFHW and Off-Centre-Fed Antennas
Read article ↗
+1
Common-Mode Noise in the Shack: Chokes, Bonding and Safety
Read article ↗
+1
Common-Mode Noise on 2 Metres: Test the Path Before the Choke
Read article ↗
+1
Common-Mode Rejection and CMRR: From Device to Installed RF System
Read article ↗
+2
Compact BOG or Full-Length Beverage? Choose for the Site
Read article ↗
+2
Comparing Antennas: Measure the Installation, Not the Label
Read article ↗Copper and Stainless Steel Bonding: PE, Lightning and RF
Read article ↗Counterpoise and Return Paths with 4:1 and 9:1 UNUNs
Read article ↗Current in Motion: How an Antenna Creates a Radio Wave
Read article ↗
+2
Currents on the Coaxial Cable: A Multi-Lane Highway of RF Behavior
Read article ↗
+2
dBi or dBd? Why I Prefer the Dipole Reference
Read article ↗
+1
DC Grounding and Static Drain in Antennas
Read article ↗
+1
DC-Grounded and DC-Open Antennas: What the Meter Does Not Tell You
Read article ↗
+2
Designing Multiband Dipoles with Off-Resonance Traps
Read article ↗
+1
Diagnosing Outdoor HF Feed-System Failures
Read article ↗
+1
Differential-Mode Noise in Solar Inverter Systems
Read article ↗
+1
Diplexers and Common Mode: Test the Hidden Coupling Path
Read article ↗
+2
Dipole Feedpoint and Shack Chokes: Control the Intended Boundary
Read article ↗
+1
Dipole, EFHW or EF-OCF: Same Wire, Different Feed Problems
Read article ↗
+1
Do I Have Enough Baluns?
Read article ↗
+1
Do Not Improvise a Coax-Shield Earth Tap
Read article ↗
+1
Do Tuners “Tune the Antenna”? Follow the Reference Plane
Read article ↗
+1
Do You Need a Kilowatt-Rated Balun at 100 Watts?
Read article ↗
+1
Does Feedline Length Matter?
Read article ↗EchoTracer3 — Technical Overview
Read article ↗
+1
Een stille ontvanger is geen stroomprobe
Read article ↗
+1
EFHW Ground Lug: RF Return, Bonding and Safety Are Different Jobs
Read article ↗
+1
EFHW Return Current: Why “Voltage-Fed” Does Not Mean Loss-Free
Read article ↗
+1
EFHW Verticals for the Upper HF Bands
Read article ↗
+2
EFHW vs EFOC: Precision Tool or Multiband All-Rounder?
Read article ↗
+1
EFHW, EF-OCF or End-Fed Long Wire: Which Fits Your Station?
Read article ↗
+1
EFHW16080 as a Shallow Inverted-U: A Practical Two-Support Layout
Read article ↗
+2
EFHWs Below 20 m: Popular, Easy—and Often the Wrong Compromise
Read article ↗
+2
EFOC and T2LT: Why They Look Similar but Are Not the Same Antenna
Read article ↗
+1
EFOC17 Coax-Counterpoise Antenna Installation Guide
Read article ↗
+1
EFOC17 Tweedraads Off-Center-Fed Dipool Installatiehandleiding
Read article ↗
+1
EFOC17-installatiehandleiding voor de coax-tegencapaciteit
Read article ↗
+1
EFOC29 Antenna Installation Guide
Read article ↗
+2
EFOC29 Antenne-installatiehandleiding
Read article ↗
+1
EFOC8 Antenna Installation and Tuning Guide
Read article ↗
+1
EFOC8 Antenne-installatiehandleiding
Read article ↗
+1
Electrically Short RX Antennas Still Notice Nearby Objects
Read article ↗
+1
Elevated or On-Ground Radials? Follow the Installed Current
Read article ↗End-Fed Antennas Explained: My Practical Multiband Choice
Read article ↗
+1
End-Fed Antennas: Choke Impedance, Current and Placement
Read article ↗
+1
End-Fed SWR Measurement: Define the Return Path and Reference Plane
Read article ↗
+1
Evenly Spaced RFI: Find the Clock, Then Find the Current Path
Read article ↗
+2
F1QM and ON6URE: The 10 m / 60 m NRT Decision
Read article ↗
+1
F4VUX's Ardennes Inverted-L: Good 80 m Results on a Real Site
Read article ↗
+2
Fan Vertical Mutual Coupling: The Tuning Trap
Read article ↗
+1
Faraday Cloth as Radials: Conductivity Is Not the Whole Test
Read article ↗
+1
Faraday Strip Radials: 23% of What, Measured Where?
Read article ↗
+1
FD4 or One-End Offset Feed: Fit the Whole Antenna
Read article ↗
+2
Feedpoint Geometry for Quarter-Wave and 5/8-Wave Verticals
Read article ↗
+1
Fixed-Phase Hybrids or Delay Lines? Receive-Array Geometry
Read article ↗
+1
Folded-Back Wire or a Final Cut?
Read article ↗
+1
Frequency Means in Off-Resonance Trap Design
Read article ↗
+1
From a Back-to-Back Trace to a Real EFHW Transformer Test
Read article ↗FullHalfWave: Shape the Current, Not Just the SWR Curve
Read article ↗
+1
Gain Isn’t Everything: SNR in Receive Phased Arrays
Read article ↗
+2
Galvanic Isolation on RX Lines: What a 1:1 Transformer Can—and Cannot—Do
Read article ↗Geometric-Mean Spacing for Multiband Receive Arrays
Read article ↗Ground Mirrors and Radials: Not All “Grounds” Are Equal
Read article ↗
+1
Ground, Grounding and SWR
Read article ↗
+1
Ground-Mounted Vertical Lengths: Quarter-Wave, Half-Wave and Five-Eighths-Wave
Read article ↗
+1
Grounding and Antennas: Separate Safety, Lightning and RF Current
Read article ↗
+1
Half-Square Feedpoints: Corner Current Feed or End Voltage Feed
Read article ↗Half-Wave Verticals Without a Ground Field
Read article ↗Half-Wave, Full-Wave or Something Else? Name the Mode First
Read article ↗
+1
Half-Wavelength Coax Does Not Repair a Mismatch
Read article ↗
+1
Ham-Radio Myths: Where the Shortcut Stops Working
Read article ↗
+2
HF vs GHz Circular Polarisation: Myths, Limits and Benefits
Read article ↗
+2
Hidden Noise Machines: How Everyday Electronics Reach Your Receiver
Read article ↗
+1
High-Power EFHW UNUN Installation: Commission the Whole System
Read article ↗
+2
High-Voltage Protection in UNUN and Balun Design
Read article ↗
+1
How an Electrically Short Active E-Field Probe Receives Low HF
Read article ↗
+1
How Clay Soil Affects an HF Antenna
Read article ↗
+1
How Far from the House? Placing an Active Receive Antenna
Read article ↗
+2
How Height Changes End-Fed Feedpoint Impedance
Read article ↗
+2
How High Should an Active Receive Loop Be?
Read article ↗
+2
How Much Choking Do You Really Need—for RX and TX?
Read article ↗
+1
Hybrid Baluns vs Separate Chokes: Follow the Current Path
Read article ↗
+1
Hybrid RF Transformers: Integration Is Not the Proof
Read article ↗
+1
If I Could Choose Only One QRO Multiband Antenna
Read article ↗
+2
Impedance and Matching: Follow the Whole RF Path
Read article ↗
+2
Inductive Loads in RF Systems: Useful, but Not Radiators
Read article ↗
+2
Inverted-L Clearance Near Metal, Buildings and Power Lines
Read article ↗Inverted-L Feedpoint Height: Follow the Whole Current Path
Read article ↗Inverted-L, Sloper or Flattop? Choose the Pattern, Not the Name
Read article ↗
+2
Is a High-Radiation-Resistance TX Antenna Always a Good RX Antenna?
Read article ↗
+2
Is Coax Balanced or Unbalanced? Follow the Current Paths
Read article ↗
+2
Is Radiation Resistance as Important for RX Antennas as It Is for TX?
Read article ↗
+1
Is There a Minimum Coax Length for an HF Antenna?
Read article ↗
+2
It All Starts With Lambda: Wavelength for Anyone
Read article ↗
+2
Johnson–Nyquist Noise: The Receiver's Thermal Baseline
Read article ↗
+2
KJ6ER Primer 2: More EIRP Is Not More Radiated Power
Read article ↗
+1
KJ6ER Primer 2: The Same 100 Watts Must Mean the Same Thing
Read article ↗
+1
Kurt Speaks Out: Transmission Lines, Chokes and Matching
Read article ↗
+2
Ladder Line: The Almost-Utopian Feedline?
Read article ↗
+2
Ladder-Line Length: Transform the Load, Don’t Worship a Number
Read article ↗
+2
Licence Classes, Loopholes and the Myth of the “Real Operator”
Read article ↗
+1
Linked Dipole or 13 m Doublet? Compare the Whole 40–10 m System
Read article ↗Loop-on-Ground: Passive Transformer or Active Interface?
Read article ↗
+2
Loops Are Not Automatically Self-Balancing
Read article ↗
+2
Maakt een nieuwe versie nu echt verschil?
Read article ↗Marine HF Antennas: Return Paths, Counterpoises and Safety
Read article ↗
+3
Matching Networks and Efficiency: Where RF Power Goes
Read article ↗
+2
Measure EFHW SWR and Resonance at the Right Reference Plane
Read article ↗
+2
Modeling Antenna Patterns with Python: What the Model Can Prove
Read article ↗
+2
Modeling Non-Resonant Traps in NEC: Measure the Network First
Read article ↗
+1
Moet een antenne resonant zijn? Kijk naar het hele systeem
Read article ↗
+1
Monoband Antennas for DX: Choose the Pattern, Not the Label
Read article ↗Mounting Flanged RF Enclosures on Masts and Booms
Read article ↗
+1
Multiband Antennas Without a Radial Field
Read article ↗Multiband EFHW Transformers: Where Ferrite and Winding Loss Appear
Read article ↗Multiband EFHWs: Why I Prefer Purpose-Built Transformers
Read article ↗
+1
Multiband Verticals and the 4:1 UNUN: Measure the Whole System
Read article ↗
+2
N-Type or PL-259 on HF: What the Antenna Actually Sees
Read article ↗
+1
Near Field, Far Field and RFI: Stop Using Wavelength as a Verdict
Read article ↗
+1
Noise Figure: When It Matters and When It Doesn’t
Read article ↗
+2
Non-Resonant Receive Antennas: What Common Mode Actually Changes
Read article ↗
+1
Non-Resonant TX Antennas on Receive: Follow the Noise Path
Read article ↗
+1
Not Every HF Antenna Is a Compromise: Define the Job First
Read article ↗
+1
NVIS Antenna Height: Design the Pattern for the Path
Read article ↗
+1
Octagon, Square or Circle? Small Receive-Loop Geometry
Read article ↗
+1
OctaLoop & OctaLoop3 Mini: Step-by-Step Assembly Guide
Read article ↗
+1
Off-Resonance Parallel-LC Trap Calculator
Read article ↗
+2
ON6URE PoTaSupreme™ eats POTA Performer for breakfast
Read article ↗
+2
ON6URE Visits SNW: A Mono-Output 80 m ARDF Receiver
Read article ↗
+1
ON6URE Visits UBA-TLS: SVXLink, Hotspots and Repeaters
Read article ↗One Month of Phasing: What We Learned About Receive Arrays
Read article ↗
+1
One Wire, No Magic: What a Goubau Line Really Proves
Read article ↗
+2
Open-Wire Feed Line: The Forgotten Low-Loss Champion
Read article ↗
+2
Open-Wire Feed Lines and Unbalanced Tuners: Why 4:1 Is Not a Default
Read article ↗
+1
Open-Wire Line, 4:1 Baluns and Tuners: Compare the Whole Feed System
Read article ↗ORA Field Day 2026: Two Stations, One Controlled RF Site
Read article ↗
+1
Our 81 m EFHW: The Low-Height Trial and Inverted-L Choice
Read article ↗
+1
Path Loss Does Not Tell You Which Microwave Band Wins
Read article ↗
+1
Potting HF Transformers: When Encapsulation Helps or Hurts
Read article ↗
+1
PowerPole 12–24 V to 5 V / 3 A PSU Family
Read article ↗
+1
QRP Z-Match vs AH-705 on a Doublet: Measure the Whole Feed System
Read article ↗
+1
Radio Weather: Kp, Solar Flux and the Path You Want
Read article ↗
+2
Raised Radials or Raised Feedpoint? Two Different Upper-HF Changes
Read article ↗
+1
Raspberry Pi and Arduino RFI: Separate Differential from Common Mode
Read article ↗
+1
Receive-Array Phasing: Geometry, Calibration and Proof
Read article ↗Reciprocity Is a Mathematical Theorem
Read article ↗
+2
Reducing Coupling in Quarter-Wave Fan Verticals
Read article ↗
+2
Refer to RF.Guru
Read article ↗Regional HF Antennas: Pattern, Height and Short-Skip Paths
Read article ↗
+1
Repeaterverantwoordelijke: geen eretitel, maar een echte opdracht
Read article ↗Responsable de relais : une vraie mission, pas un titre honorifique
Read article ↗
+1
RF Ground: Name the Current Path
Read article ↗
+3
RF in the Shack: Skin Effect, Exterior Current and Common Mode
Read article ↗
+2
RF.Guru’s Coating Process: Why It Cannot Be Rushed
Read article ↗RG402 Common-Mode Chokes: Cable, Ferrite and Bend Limits
Read article ↗
+1
RX Chokes: Stop Thinking Only Like a Transmitter
Read article ↗RX vs TX Antennas: Same Physics, Different System Objectives
Read article ↗
+2
RX vs TX Grounding: Same Physics, Different Questions
Read article ↗
+1
Sailing-Vessel Antennas from HF to UHF
Read article ↗
+1
Seven-Band EFHW vs Terminated Loop: A Flat SWR Is Not the Verdict
Read article ↗
+2
Shielded Balanced Feed Lines: Twinax, Dual Coax and the HF Trade-Off
Read article ↗
+1
Shielded Loops: What the York Study Means for Our Designs
Read article ↗
+3
Short Radials and Rudy Severns: Read the Test Before the Rule
Read article ↗
+1
Shorted Quarter-Wave Stubs in Monoband RF and Surge Systems
Read article ↗
+2
Six Feet of Radials Is Not a Universal Ground-System Rule
Read article ↗
+1
Skin Effect in Receive Antennas: Real Physics, Bounded Impact
Read article ↗
+1
Sleeve and Clip-On Ferrites at QRO: Measure the Finished Choke
Read article ↗Sloping a 160/80 m Inverted-L EFHW: What Really Changes?
Read article ↗
+1
Small-Space HF Wire Antennas: Choose the Constraint First
Read article ↗
+1
Solar Inverter RFI: From Noise Observation to EMC Evidence
Read article ↗
+2
Solar RFI on a Beam: Find the Coupling Path First
Read article ↗
+1
Solid-State Amplifiers, Multiband Wires and the Load a Tuner Must Handle
Read article ↗SP3L, Stray Capacitance and the Limits of Y21 Choke Measurements
Read article ↗Stop Cutting Coax to “Fix” SWR
Read article ↗
+1
SWR and Coax Loss: Manage the Real Heat
Read article ↗
+2
SWR Is a Reference-Plane Measurement, Not an Efficiency Meter
Read article ↗
+2
SWR, Reflected Power and Real Feed-Line Loss
Read article ↗
+1
SWR, Resonance and Radiation: Read the Right Measurement
Read article ↗
+2
T2LT Antenna: Where the Coax Stops Feeding and Starts Radiating
Read article ↗
+1
Tapped RF Autotransformers: Ratio, Return Path and Common Mode
Read article ↗
+1
Terminated Loops, EFHWs and BBTDs: Follow the Watts
Read article ↗
+2
TerraBooster Placement: Give the Whole Loop Clear Ground
Read article ↗
+3
The 80–10 m EFHW Myth: Useful Antenna, Not Magic Antenna
Read article ↗
+2
The Copper Rod Before the Shack: A Misguided Ritual
Read article ↗The Counterpoise Is Part of the Antenna, Not an Optional Wire
Read article ↗
+2
The Destructive Null: When Directionality Bites Back
Read article ↗The Double-Bazooka Dipole Is Not Antenna Medicine
Read article ↗
+1
The Doublet Is a Feed-System Decision, Not a Magic Length
Read article ↗The EFHW Capacitor Is a Shunt Branch—Inside a Complete Network
Read article ↗The EFHW Capacitor Trap: Choose the Antenna Before the SWR Dip
Read article ↗
+2
The EFLW37: A Practical 37-Metre End-Fed Wire
Read article ↗
+1
The EH Antenna: What Physics Predicts and Measurement Must Prove
Read article ↗
+1
The End-Fed Half-Wave Myth: Why Most EFHWs Are Doing It Wrong
Read article ↗
+2
The Guanella Transformer: Current Balun and UNUN Explained
Read article ↗
+2
The Ham’s Obsession with Resonance
Read article ↗
+1
The History of RF Transformers: From Induction to Transmission-Line Networks
Read article ↗
+1
The Limits of NEC: Model the System You Actually Built
Read article ↗
+1
The Myth of the Random Wire Antenna
Read article ↗
+1
The Patron Saint of Ham Radio Had a Callsign
Read article ↗The Real Engineering Behind Motorized HF Antennas
Read article ↗The Ruthroff Transformer: Voltage Action, Balance and Common Mode
Read article ↗
+1
The SWR Myth and the Case of the “Lost” Power
Read article ↗
+1
The Ugly Balun: Measure the Coax Choke Before You Mock It
Read article ↗
+2
Thick Aluminium Tubes or Thin Wire?
Read article ↗
+1
Three-Element Triangular Array Spacing and NEC-2 Calculator
Read article ↗
+1
Thunderstorm Safety for Amateur Radio: Disconnecting Is Only One Layer
Read article ↗
+2
Thévenin Equivalents in Receive Systems
Read article ↗
+2
Tinned-Copper Braid and Aluminium Masts: Build the Bond, Not the Myth
Read article ↗To Resonate or Not? Ask What the Antenna System Must Do
Read article ↗
+1
Trapped in a Trap: What Coaxial Traps Really Trade
Read article ↗
+1
Tuning a 160/80 m EFHW Inverted-L for SSB DX
Read article ↗
+2
Tuning a Doublet: Match the Whole Feed System
Read article ↗
+1
Two Inverted-L End-Fed Wires for a 160/80/40 m Station
Read article ↗
+1
Type 316 Stainless Steel in Outdoor RF Hardware
Read article ↗Understanding Antenna Gain and Radiation Patterns
Read article ↗
+2
Understanding Current Taper in Receive Antennas
Read article ↗
+2
Understanding IP3: What It Is and What It Isn’t
Read article ↗Understanding Polarization: Why It Matters for Your Antennas
Read article ↗
+2
Understanding the Null of a Shielded Active H-Field Loop
Read article ↗
+2
UNUN or Current Balun? Let the Installed Load Decide
Read article ↗
+1
UNUN Types: Ratio, Topology and Common-Mode Control
Read article ↗
+1
Vergunningsvrij is niet regelvrij
Read article ↗
+1
Vertex-Fed Delta Loop or V-Dipole for Inter-European Paths?
Read article ↗
+2
Vertical Antennas for DX: Why Size and Shape Matter Across the Bands
Read article ↗
+1
Vertical Antennas: Horizontal Clearance and DX Success
Read article ↗
+1
Vertical E-Probes for DX and NVIS: Choose the Useful Pattern
Read article ↗
+1
Vertical Radiator Diameter: When Tubing Beats Wire
Read article ↗
+1
Vertical-Antenna Ground Systems: Radials, Earthing and Lightning
Read article ↗
+1
VertiCore 1/4th: The Reliable Workhorse for 15, 17, and 20 m
Read article ↗
+2
VertiCore 5/8λ for 4, 6, 10 and 12 m
Read article ↗
+2
VertiCore Monoband Series: 1/4λ and 5/8λ — Technical Overview
Read article ↗
+2
VertX Fan Vertical: Why Matching Is Not Pattern Control
Read article ↗VertX Technical Architecture: Fewer Resonators, Better-Controlled Currents
Read article ↗VHF/UHF Hotspot and PCB Noise: A Hands-On EMC Investigation
Read article ↗
+1
Wait—Aren’t Those the Same Antenna?
Read article ↗
+1
Weatherproofing Outdoor RF Connectors
Read article ↗What a 50-Ohm Load Can Tell You About a Ladder-Line Balun
Read article ↗
+1
What a “40 dB Choke” Number Actually Means
Read article ↗What an Inline SWR Meter Actually Measures
Read article ↗
+1
What Ben Witvliet’s NVIS Research Shows About Circular Polarisation
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+2
What Happens When the Ferrite Core Stops Being a Standard Shape?
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+1
What Is the Biggest Effect of a Line Isolator?
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+1
What the Ground Lug Changes When a Transmit Antenna Receives
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+1
When a Dedicated Receive Antenna Helps
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+1
When a Robotic Lawn Mower Reaches Your Receiver
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+1
When an External Antenna Tuner Helps a Short Wire
Read article ↗When Does CAT5 Start to Radiate?
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+1
When Ferrite Runs Hot: Core Loss, Flux and Real Power Limits
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+1
When Is a Rotator Useful on an Active Magnetic Receive Loop?
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+2
When Lowering an Inverted-L Feedpoint Barely Moves SWR
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+1
When Receive Arrays Help More Than a Big Yagi in Contesting
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+2
When Required Bonding Carries RF: Keep Safety, Control Current
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+1
When Size Matters Less: Receive Antennas Below One-Twelfth Wavelength
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+2
When the Better SWR Curve Lost the Field Test
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+1
Where Does the Noise Come From?
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+1
Where the Current Flows, the Signal Grows
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+2
Why 10 and 12 Metres Move When a Wire Becomes an Inverted-L
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+2
Why a 6:1 UNUN Is Not Our Default for High-Power HF
Read article ↗Why a MMIC Can Look High-Impedance Below Its Intended Band
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+2
Why a Perfectly Symmetric Loop Often Isn’t—Especially When It’s Low
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+2
Why an Active Antenna Still Needs a High-Dynamic-Range Receiver
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+1
Why an LNA Won’t Fix Your Receiver’s Dynamic Range
Read article ↗Why Coax? The Practical and RF-Physics Advantages of Shielded Feedline
Read article ↗Why I Choose the EFOC17 for 40–10 m Operation
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+1
Why I Prefer an EF-OCF for Many Camper Installations
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+2
Why I Prefer EFOC29 over an All-Band EFHW or Long Wire
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+1
Why I Start With a 4:1 UNUN for Non-Harmonic Multiband Wires
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+1
Why I Won’t Trust a Ferrite Stack to Casual Glue or Tape
Read article ↗Why IP68 Enclosures Can Still Develop Moisture Inside
Read article ↗Why Is There a Gap on My RF.Guru Enclosure?
Read article ↗Why I²R Matters: Where RF Current Becomes Heat
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+2
Why Low-Band EFHW Installations Can Be Touchy
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+1
Why RF.Guru Builds Narrower-Band EFHWs for High Power
Read article ↗Why RF.Guru EFHWs Do Not Use Shunt Compensation Capacitors
Read article ↗Why RF.Guru Focuses on HF Receive Systems, Not Beams
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+1
Why RF.Guru Uses a 4:1 UNUN and a Separate Choke
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+1
Why Some EFHWs Eat Your Signal—and Why I Favour EFOC
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+1
Why Transients Matter in an Amateur-Radio Station
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+2
Why We Avoid Heavily Helical-Loaded 40 m Antennas
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+2
Why We Designed EchoTracer3 Instead of Copying the MiniWhip
Read article ↗Why We Love Doublets—and When a G5RV Becomes a House of Cards
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+2
Why We Prefer an Inverted-L for Low-Band EFHW Antennas
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+1
Why We Stepped Back from the 80–10 m EFHW
Read article ↗Why We Still Use 600 Ω Open Wire—and When Window Line Is Better
Read article ↗Why We Use Polycarbonate for Our QRO Enclosures
Read article ↗Why We Use Simplified Antenna Models—and When We Use NEC
Read article ↗Why You Might Not Need NEC for the First Active-Array Model
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+1
Wideband RF Phasing Networks: Materials, Balance and Calibration
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+1
Wilkinson Dividers for RX: Isolation, Loss and Alternatives
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+1
Wim’s OT8M Inverted-L: Fitting 160/80 m to the Contest Station
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+2
Wire Antennas on Sloped Terrain: Level, Follow the Ground or Aim the Pattern?
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+2
Wire Length and Wavelength: Sloper, Flat-Top or Inverted-L?
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+2
Your Body Is Not a Line Isolator
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+2
µPaddle Setup, Calibration and Care
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+1
“Ground Is a Myth”—Until You Name the Current Path
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+1