Knowledge Base: Guides & Technical Resources

Welcome to the Knowledge Base, your comprehensive resource for improving your understanding of antennas, RF systems, and station optimization. Whether you’re new to amateur radio or an experienced operator, this collection of articles is designed to provide practical advice, technical insights, and solutions to common challenges faced in antenna design, installation, and performance tuning.

The articles are divided into key categories to help you easily navigate through the topics that matter most to your station’s setup and operation.

Wire Antennas

1. Advice on Wire Antennas for Those with Limited Space
2. Does feedline length matter?
3. Fold-Back Tuning for Antennas: Guidelines and Best Practices
   
4. Tuning a Doublet Antenna: Methods and Considerations
5. Why a 600-Ohm Open-Wire Doublet with a Z-Match is More Efficient Than a 450-Ohm System with an Asymmetric Tuner
6. QRP Z-Match vs QRP Autotuner with Doublet and 600-Ohm Open Wire – Is a Z-Match More Efficient?
7. Comparing a Linked Dipole vs a 13-Meter Doublet Antenna with 600-Ohm Ladder Line
8. Understanding Radiating Wire Length vs Wavelength in Sloper, Flat-Top, and Inverted-L Antennas
9. Optimal Mast Height for NVIS Transmission Antennas

End Fed Wire Antennas

1. End-Fed Antennas Explained
2. Using an Antenna Analyzer for End-Fed Antennas with Coax as a Counterpoise
3. Feed Point Impedance vs. Feedpoint Height Above Ground for End-Fed Antennas
   
4. Why the EFOC29 Design Outperforms the EFHW8010 and EFLW37 in Multiband Operation
   
5. Why the EFOC17 is the Better Choice for 40M to 10M Operation
6. Why a (External) Tuner is handy to get more out of your (too short) wire antenna
7. Optimizing End-Fed Antennas with High-CMR Chokes
8. Why an Antenna Tuner Is Essential When Using Multiband Wire Antennas with Solid-State Amplifiers
   
9. Why a Near-Resonant Antenna Like the EFOC29 Is Preferable to a Long Wire: EFOC29 vs. EFLW22
10. The EFLW51: A Quick-and-Dirty Compromise for 160m
    
11. The EFLW37: A Quick-and-Dirty Antenna for 80m Local Work
    
12. Understanding the Role of the Counterpoise in 4:1 and 9:1 Antennas
    
13. Why We Prefer a 4:1 UNUN for Wideband Multiband Wire Antennas Without Harmonic Relationships
14. The Hidden Truth About the Counterpoise: It's Not What You Think!
15. EFHW, EFOC, and EFLW Explained: Which End-Fed Antenna Is Right for You?
16. Understanding Antenna Current Distribution and Impact on Performance

EFHW End Fed Half Waves Explained

1. The End-Fed Half-Wave Myth: Why Most EFHWs Are Doing It Wrong
   
2. The Hidden Trap of EFHW Transformers: How "Magic Capacitors" Fix One Problem But Create Another
3. Why Wideband EFHW Transformers Like the 49:1 Are Not Truly Wideband
4. The Back-to-Back EFHW UNUN Transformer Measurement Myth
5. EFHW vs. EFOC: Two Voltage-Driven Antennas, Two Smart Solutions
6. The Challenges of Multiband End-Fed Half-Wave (EFHW) Antennas and Ferrite Losses
7. Comparing a 15m and 20m Mast for a Dual-Band 160/80m EFHW Inverted-L
8. Why RF.Guru Pushes Dual-Band EFHW for High-Power (3kW-4kW)
9. Why RF.Guru Recommends Only Inverted L for 160/80M and 80M/40M with 68-70:1 Transformers for end fed antennas
10. Why an EFHW Inverted-L for 160m/80m outperforms a 20m long vertical with a Tuner
    
11. Why an EFHW Inverted-L for 80m/40m Outperforms a 10m or 13m long Quarter-Wave Vertical
    
12. Why We Primarily Use Full-Wave and Half-Wave End-Fed Antennas
13. EFHW vs. EFOC: Two Voltage-Driven Antennas, Two Smart Solutions
14. The FullHalfWave Series (EF FHW): Dual Half-Wave EFHWs Reimagined for Real-World DX
15. Comparing 80/40 Meter EFHW Antennas: Inverted L vs. Sloper/Flattop for DX and NVIS Operations
16. These Two Inverted L End-Fed Antennas Will Crush DX on 160/80m and 80/40m
    

Non-resonant Traps

1. The Power of Non-Resonant Traps: A Smarter Way to Multiband Dipoles
   
2. Nextgen Non-Resonant Traps: Engineering Performance through Frequency Means and Symmetry
3. The FullHalfWave Series (EF FHW): Dual Half-Wave EFHWs Reimagined for Real-World DX
4. Non Resonant Trap Calculator for Dipoles and EFHWs
   
5. Non-Resonant Traps (NRTs) and Their Simulation in NEC Tools

Vertical antennas

1. Why Clever Antenna Trickery Doesn’t Always Pay Off – A Real-World Test
2. Multiband Fan Verticals and Why Mutual Coupling Isn’t a Big Deal
3. Reducing Mutual Coupling in 1/4-Wave Fan Verticals

Why We Won’t Offer What Everyone Else Does

1. We’re Done with the EFHW4010 and EFHW8010
2. In Praise of Doublets (And Why the G5RV Is a Card House Made of Apple Cake)
   
3. Why We Don't Build a 6:1 UNUN for High Power Applications
4. Coiled Into Compromise: The Truth About Loading Coils in Shortened End-Fed Antennas
5. Trapped in a Trap: (Coaxial) Traps in Multiband Antennas
6. The FD4/Windom Antenna: A Deprecated Classic and Why the EFOC29 Is a Better Choice
   

Active Receive Antennas

1. Is a TX antenna (with high radiation resistance) always a good RX antenna?
2. Is radiating resistance as important for RX antennas as it is for TX Antennas?
3. Comparison of our Active RX Antennas
   
4. RX vs TX Antennas: A Fundamental Difference
   
5. Why an Octaloop is Superior to a Square or Circular Loop Antenna
   
6. Understanding the Null of a Shielded Active H-Field Loop Antenna
7. Height vs. Performance: Optimizing the OctaLoop Active Magnetic Loop Antenna
   
8. Active RX and TX Antenna Proximity: Safe Distances and RF Protection
9. Safe Distance for Active Antennas from the Home
10. Why MMICs Behave as High Impedance Below Their Intended Frequency Range
    
11. Mounting the Vertical Vortex
    
12. When Is a Rotator Useful on a Active Magnetic Receive Loop?
    
13. Why Most RX Antennas Excel at DX Reception Compared to Multiband Wire Antennas, Verticals and even Yagis
    
14. The Future of RX: aRFoF vs Coax in QRM-Challenged Environments
15. Why You Still Need a High Dynamic Range Radio—Even with an Active Antenna

Engineering Choices: The What, Why & How Behind Our 'Build to Last' Products

1. Why High Quality Polycarbonate Enclosures
2. Understanding the Visible Gap on Our Enclosures
   
3. Why IP68 Enclosures Still Suck Up Water – And What You Can Do About It
   
4. Why Cheap ABS Plastic Is Bad for High Power RF Baluns and Chokes
   
5. Why Does RF.Guru Use PTFE-Tinned Stranded Copper Wire for Baluns Instead of Enameled Wire?
6. Why We Don't Use Resin Potting for Our Baluns
   
7. Why Gluing Ferrite Cores with Super Glue or Taping Them is a Bad Idea
   
8. Stainless Steel Type 316: Properties, Benefits, and Applications
9. Correct Use of RF.Guru Antenna Tuner Baluns
10. Mounting Flanged Enclosures on a Boom, Mast, or Support Tube
    
11. RF.Guru Coating Process: Why It Matters and Why It Can't Be Rushed
    
12. Why We Use ASA for Outdoor Structures
13. Want to refer to us ?

Baluns and Ununs

1. The History of RF Transformers
2. A brief overview of BALUN types and their applications
3. A brief overview of UNUN types and their applications
4. The Guanella transformer (Current Balun/UNUN) explained
5. The Ruthroff transformer (Voltage Balun/UNUN) explained
6. The Autotransformer (Voltage Unun transformer) explained
7. The Hybrid transformer explained
8. Autotransformer vs. Ruthroff Transformer in UNUNs and BALUNS
9. Don’t Make This Mistake: Why RG402 is the Worst Choice for Common Mode Chokes
   
10. Understanding Ferrite Coupling Efficiency Across Coaxial Cable Shield Types
    
11. Why Measuring Your Coax Shield with a VNA Still Doesn’t Prove Your Choke Works
    
12. Debunking Common Myths in Common-Mode Choke Measurements with a VNA
    
13. Proper Grounding and Choking to Eliminate Common Mode Noise in the Shack
    
14. The dual roles of a 1:1 UNUN vs Line Isolator or Choke
    
15. Currents on the Coaxial Cable – A Multi-Lane Highway of RF Behavior
16. Unlocking Wideband Phasing in Amateur Radio with Modern Ferrite Materials

Grounding and safety

1. Grounding Practices, Safety, Performance, and Regulatory Compliance
2. Ground, Grounding and SWR
3. The Use of INOX Stakes as High Impedance Termination Points for RX Shielding and EFHW Counterpoise
4. RX vs TX Grounding — Totally Different Games

General Technical Articles

1. The Importance of a High-Quality Common-Mode Choke or Line Isolator
2. Understanding Power Specifications: ICAS, CCS, and DIGITAL in Amateur Radio
   
3. Minimizing RF Noise in the Radio Environment
   
4. Optimal Common-Mode RF Current and Noise Elimination for TX antenna
   
5. Propagation Characteristics of Ham Radio Bands (2200m-2m) Mid-Europe
6. Why is Targeting Zero Reactance (X = 0) Important When Tuning an TX Antenna?
7. Reducing RF Interference from Solar Panels: How to Mitigate Noise on Your Beam Antenna
8. Why You Need At Least Three Chokes in Your Antenna System
   
9. Remote Tuners: Stop Putting Them Where You Don’t Need Them
10. General Antenna Tuning Advice, where to place the resonance dip?
11. Tuning Your Antenna System Using Coax Cable Length
    
12. VSWR vs dB Loss (S11 and S21): Cutting through the common confusion
    
13. Reflected Power Isn’t Lost Power: Debunking the SWR Myth in Tuned Antenna Systems
    
14. Why You Need a 1:1 BALUN or UNUN on Every Antenna: The Forgotten Role of Skin Effect
    
15. Why Your Windom Antenna is Holding You Back — And What to Use Instead
    
16. The 5 Silent Killers of Your Power Amplifier (and How to Avoid Them)
    
17. The Perfect SWR of 2:1 on an Inductive Load? Or Not?
    
18. Why the 21st Century Belongs to Active E- and H-Antennas (and the Yagi Might Be Dead)
    
19. Yagi Antennas: Common Mode Listening Machines

Operating Advice

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

RFI - Radio Frequency Interference.

1. Hidden Noise Machines: Understanding EMC in Everyday Electronics [NL]
2. EMC Nightmare: When Solar Inverters Become Illegal Transmitters [NL]
3. When Your Lawn Mower Becomes an Interference Source: EMC Warnings for RF Enthusiasts

Ham Radio 101: The RF Engineering Behind the Signals

1. What Common-Mode Really Means — And Why Hams Get It Wrong [NL] [FR]
2. It all starts with Lambda ... [NL]
3. Why I²R Matters [NL]
4. DC Grounded vs Open Antennas
5. #1 Mistake Hams Make During Thunderstorms—Fix It Before It's Too Late
6. The Inductive Load: Why It’s the Convenient Radiator in RF Systems
   
7. RF in the Shack: It's Skin Effect, Not Common Mode
   
8. Why Resonance Isn’t Always the SWR Sweet Spot
   
9. Radio Weather: K-Index, Solar Flux, and More
   
10. Physical Length vs Electrical Length — What's the Difference?
    
11. The Truth About SWR, Resonance, and Efficient Radiation
    
12. Antenna Tuners Don't Tune Antennas: The Transmatch Misconception

Debunking Myths in Ham Radio

1. The Back-to-Back EFHW UNUN Transformer Measurement Myth
2. Debunking the 4:1 Balun Myth for Open-Wire Feedlines into Asymmetrical Tuners
3. SWR Demystified: Understanding the Real Impact of SWR on Your Station
4. Reciprocity Is a Mathematical Theorem
   
5. ON6URE PoTaSupreme™ eats POTA Performer for breakfast
6. The Hidden Truth About the Counterpoise: It's Not What You Think!

Frequently Asked Questions and their Answers

1. Common Misconceptions in Ham Radio
2. Common Issues and Their Solutions
3. Are There Any Truly Efficient Multiband 160M-10M or 80M-10M Wire Antennas?
   
4. Why Do I Need a Kilowatt-Rated BALUN If I Only Run 100 Watts?
   
5. If You Could Choose Only One QRO Multi-Band Antenna, Which One Would It Be?
   
6. Debunking the Height Myth: Why a 20M Yagi May Not Be Your Best Choice
   
7. What Is the Biggest Effect of a Line Isolator?
   
8. Why Choose a +45 dB Line Isolator? The Benefits Over Standard Chokes
   
9. Why a LineIsolator at the Transceiver and a Balun on a Dipole Are Always Necessary
   
10. To Resonate or Not to Resonate – That’s the Ongoing Question… [NL]

Smoke & Mirrors: Tales from the RF Underworld

Where theory meets creative interpretation — and common sense takes a coffee break. Dive deep into the shadowy alleys of the RF underworld, where coax gremlins whisper sweet SWR lies, endfeds defy physics (barely), and every backyard guru has a “proven” method involving coat hangers, moon phases, and unicorn baluns. A must-read for those with a wicked mindset, a soldering iron in one hand, and a raised eyebrow in the other.

1. The 10 Worst Ham Radio Antennas of All Time
2. The Magical Mystery Wire: Confessions of the End-Fed Believers
   
3. Reciproke or Go Broke: Why Your "Universal" Antenna Belongs in a Museum
4. NECtasy and the Myth of the Perfect Polar Plot
5. The Cult of Reciprocity™ – CMR is a Conspiracy, RDF is Elitism and Patterns are Truth

ON6URE on the road ....

1. ON6URE Visits SNW: innovative 80-meter ARDF receiver

Collaborations

At RF.Guru, many of our products and designs begin with a simple question or suggestion from fellow radio amateurs. Whether it’s a unique installation challenge, a request for better multiband coverage, or just a creative idea sparked in an email exchange — these conversations often evolve into full design studies, prototypes, and sometimes even commercial solutions.

This section highlights such collaborations: real-world problems, smart operator input, and the technical journey we took together to create practical and performance-driven solutions. Your input doesn’t just matter — it shapes what we build next.

1. Dual-Band 10m / 60m Inverted-L with NRT: A Collaborative Design with F1QM

EndFed Antennas Installation guides

1. EFOC29 Antenna Installation Guide
   
2. EFOC17 Antenna Installation Guide
   
3. EFOC8 Antenna Installation Guide
   
4. Optimizing the EFOC29 for 160m-10m Band Operation with additional Radials

Doublet Antennas Installation guides

1. Mounting a 44m Doublet on a 16m Pole with 16m 600Ω open-wire feedline
   
2. Mounting a 31m Doublet on a 10m Pole with 16m 600Ω open-wire feedline
   
3. Mounting a 80m Doublet on a 16m Pole with 16m 600Ω open-wire feedline
   

UNUN and BALUN Installation guides

1. General UNUN user installation guide & safety instructions
2. General BALUN user installation guide & safety instructions
3. General LINE ISOLATORS user installation guide & safety instructions
4. General ANTENNA TUNER BALUN user installation guide & safety instructions

PCB Products Installation guides

1. 2023-P-811 PowerPole Power HAT for Raspberry Pi  Installation Guide
   

Hotspot, Transceiver, Receiver and Repeater modules troubleshooting 

1. Troubleshooting Man-Made Noise on Hotspot, Transceiver PCB's and Devices (VHF/UHF)