Build an Ultra-Portable End-Fed Antenna for QRP: Step-by-Step Guide

A ham radio operator running QRP field operations

Portable Ham Radio Antennas: The Best Lightweight End-Fed Build

Introduction

If you’re into QRP (low-power) radio operation, you’ll appreciate this ultra-portable end-fed antenna designed by David Del Torimo (DL1DN). It’s lightweight, efficient, and perfect for field use—ideal for operators who want to maximize performance with minimal gear.

Why does this matter? In QRP, every watt counts. A well-tuned end-fed antenna can mean the difference between a weak signal and a reliable connection, even at just 5 watts or less.

In this article, I’ll break down David’s build, go over the key components, and share a video at the end that dives deeper into optimizing your QRP setup.

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Creator Bio

David Del Torimo (DL1DN) is a passionate QRP operator and antenna experimenter. His QRP Lifestyle channel is packed with hands-on tips and DIY projects for ham radio enthusiasts, with a special focus on lightweight, efficient, and portable antenna setups.

🔗 Check out his channel for more QRP hacks: QRP Lifestyle on YouTube

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Key Takeaways And Notes

1. End-fed antennas are great for QRP. This build uses a 64:1 UNUN transformer for efficient impedance matching.
2. Portability matters. Weighing just 58 grams, this antenna is perfect for field ops and backpacking.
3. Tuning is everything. The right inductance and capacitance ensure your antenna works across multiple bands.

4. Some Notes About This Article

   1. 64:1 UNUN Transformer Misconception – The article states that the end-fed antenna uses a 64:1 UNUN, but this may not be suitable for all end-fed antenna configurations. A 49:1 UNUN is more commonly used for end-fed half-wave (EFHW) antennas, while a 64:1 is used for much higher impedance antennas (e.g., random wires requiring additional tuning).

   2. Toroid Core Selection – The FT50-43 toroid may not be ideal for a 64:1 transformer. This core is small and may not handle power efficiently. Larger cores like FT82-43 or FT140-43 are more commonly used in QRP applications.

   3. Inductor Value Issue – The article specifies a 34 µH inductor, but this value depends on the wire length and frequency range. If this is for a multi-band operation, the inductor value may need adjustment.

   4. Antenna Wire Length Inconsistency – The given lengths (0.95m + inductor + 2m) do not align with common resonant wire lengths for typical end-fed antennas. A traditional EFHW for 20m band should be around 10m (half-wave for 14 MHz) or a harmonic multiple.

   5. Capacitor Misplacement – A 100 pF, 1000V capacitor in the described position suggests it is being used for impedance matching, but EFHW antennas do not always require this. Typically, a capacitor (e.g., 150 pF - 220 pF) is placed across the transformer output to improve high-frequency performance.

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Materials You'll Need

Item	Purpose
SMA connector	Connects the antenna to your radio.
FT50-43 toroid	Acts as the core for the impedance transformer.
Insulated copper wire	0.25mm enamel wire recommended for winding.
Capacitor	100 pF, 1000V for circuit stabilization.
PVC pipe (28.5mm)	Used as a coil form for the inductor.
Glue or resin	Provides insulation and mechanical support.

Building The Antenna: 

1. Wrap the Toroid Wind two bifilar turns, followed by seven turns in one direction. Cross the toroid and wind seven more turns in the opposite direction. Keep the crossing wire slightly to the side to make SMA connector installation easier. 2. Add the Inductor Wrap 50 turns of wire around a 28.5mm PVC pipe. The inductor should measure 34 µH for best performance. 3. Connect the Antenna Wire Attach 0.95m of wire, then connect the inductor, followed by another 2m of wire. 4. Finalize the Circuit Install a 100 pF capacitor (1000V) between the center conductor and ground. Solder all connections and insulate them with glue or resin.

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Resources Mentioned

• FT50-43 Toroid – Ensures efficient impedance transformation.

• 100 pF, 1000V Capacitor – Helps balance and tune the antenna for a better SWR.

• 28.5mm PVC Pipe – Used for winding the inductor to add inductance.

Terms Explained

• QRP – A ham radio term for low-power transmission, usually 5 watts or less.

• End-fed antenna – A type of antenna where the feedpoint is at one end of the wire, commonly used for portable operations.

• 64:1 UNUN transformer – A type of impedance-matching transformer that converts high antenna impedance (~3200Ω) to a lower impedance (50Ω) suitable for radios.

• Impedance matching – The process of ensuring efficient power transfer between components, reducing signal loss.

• SWR (Standing Wave Ratio) – A measure of how well an antenna is tuned; lower SWR means better efficiency.

• FT50-43 toroid – A ferrite ring (toroid) with specific magnetic properties used for building transformers.

• Inductor – A coil of wire that stores energy in a magnetic field, affecting the tuning of the antenna.

• Capacitor (100 pF, 1000V) – A component that stores electrical charge, helping balance the antenna’s tuning.

• µH (Microhenries) – A unit of inductance used to measure the magnetic storage ability of a coil.

• Bifilar winding – A method of winding two wires together on a core to improve efficiency.

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Best Advice for QRP Operators

From my experience, tuning makes all the difference. Even with the best rig, a poorly optimized antenna will hold you back. Always measure your inductance, capacitance, and SWR before heading out. And when you’re running QRP, remember—every watt counts!

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FAQ

1. What is an end-fed antenna?

An end-fed antenna is a long wire antenna that is fed from one end, making it ideal for QRP and portable operations.

2. Why use a 64:1 UNUN transformer?

It helps match the high impedance of the antenna (~3200Ω) to your radio’s 50Ω coax input, reducing loss and improving efficiency.

3. Can I use a different toroid core?

Yes, but FT50-43 is optimized for this impedance transformation. If you use a different core, you may need to re-tune the circuit.

4. What bands does this antenna work on?

Primarily 20m, but with proper tuning, it can cover multiple bands.

5. How do I pack this antenna for transport?

David suggests using a rope ring to relieve stress on the connections and prevent breakage.

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Watch David (DL1DN) Build The Ultra Lightweight End Fed QRP Antenna System