Building the Ultra Light EFHW Antenna Kit

Updated: Jul 27

I have written this article as a guide to building a Radio-Stuff Ultra Light EFHW antenna Kit.

The kit itself comprises of;

Single Fair-Rite T50-43 core
M3 fittings including wing nut and solder tab
100pf capacitor
Approx. 1m enamelled copper wire
BNC connector
Approx. 10.25m green SOTA wire
Kite winder and 30m nylon string

These kits are quite easy to assemble with the exception of the 49:1 transformer. Here are a few tips.

Firstly check everything is there. Then cut the wire in half so you have about 50cm to work with. Bend over the end on itself by about 12-13cm to give you a hoop.

You will then need to wind the bent section together to give you bifilar windings.

You will need to pass the bifilar windings through the core twice, then five more turns of the single wire to give you seven turns on the toroid. You then pass the wire across through the toroid centre, then six more windings to give you a total of 14 windings with 2 bifilar giving a 49:1 transformer, see below.

Then cut the excess of the wire. I use a soldering iron to then burn off the enamelling at the ends of the wires.

You then need to push the end of the wires through the holes. It is important to push the bifilar windings through marked bifilar.

It's then just a case of soldering all the components into place.

You can see above I have connected the antenna wire by making a not through one of the strain relief holes and then soldering the wire to the solder tab. All held together using the nuts and bolt.

P.S. there is one mistake on the circuit board. See if you spot it.

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