Multiband End Fed Half Wave (EFHW) Antenna for 40-20-10m or 30-17m

Multiband End Fed Half Wave Antenna

The design of the antenna comes from Frank N4SPP, who presented it originally on his web page Multiband End Fed, which is now unfortunatelly archived. Click on the link to visit the Internet Wayback Machine version to read about his extensive tests.

The antenna is to be wired as follows:

The key benefits of this antenna are:

• You do not need too much of radials if any (high voltage feed point)

• It is end-fed reducing the need for lengthy coax at a potentially unpractical feedpoint

• Can be tuned to work without a tuner on multiple bands

• Can be used in horizontal or vertical configuration

The Loading Coil

I have created a 3D model of the loading coil former that has following benefits:

• It has a thread which helps winding the wire and which separates the turns from shorting,

• It has a center hole which exactly fits my DX-Wire fibreglass mast so that I do not have to secure it in any other way,

• The wire terminals are standard Wago 221 wire clamps.

The Wago clamps are holding in place only by pressure, there is a little notch helping this. That is the method even the original Wago clamp holders are using.

The screws do not tap to the plastic material, there is a nut inside of the coil former. It has to be held in place by small pliers before the thread taps.

Coil inductance: 34uH

The 1:64 Impedance Transformer

The transformer is converting the high-impedance of the half-wave antenna to 50 ohm impedance good for your coax and transceiver. Frank originally used FT240-43 core to bifilarly wind the transformer, claiming it will withstand 50-60W continuous. I have built smaller and bigger core versions, for portable QRP or digital 100W usage at home.

The transformer is to be wound like in the figure above. Reffer to the diagram at the very top for wiring. You can add a short counterpoise wire for the antenna to be more gentle when tunning (by cutting the antenna wire). Also if you install it at a permanent location it makes sense to ground it via 1M resistor to bleed any static which builds up during rainy days etc.

The Antenna Wire

40-20-10m version

Wire between 64:1 balun and the coil: 10.1m
Wire between coil and antenna tip: 1.85m

30m-17m version

I wanted to have coverage of 30m and 17m with the same concept of an antenna. I have just simply tried in the backyard empirically and it turned out that with the same coil, I could cover 30m and 17m!

Wire between 64:1 balun and the coil: 7.48m
Wire between coil and antenna tip: 0.83m