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.

160 published engineering articles

Four fixed starting points

Start at the front bench

The story, the mission, the collaborations and the corner where the smoke is mostly intentional.

Measured, reviewed, published

The article library

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The Guru's Incredible Lab

Start at the front bench

The article library

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

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

Shared 868 MHz Airtime: The Commons Is Real, but Measure It Properly

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

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

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

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

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

Ferrite Sleeves vs Wound Cores: Compare the Measured Choke

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

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

The Transmission-Line Model Is Not the Whole Electromagnetic Reality

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

Build the Station Around the Bottleneck

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

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

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

When a Better Choke Makes the SWR Look Worse

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

Shack Counterpoises: RF Return Paths Without Defeating Safety

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

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

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

Do Antennas Attract Lightning? Geometry, Attachment and Risk

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