domenica 11 agosto 2013

1/2 Lamba end feed Fuchs Antenna Tuner

The Fuchs Antenna was introduced by Arwed Fuchs, an Austrian Radio Amateur in 1928. 
It was used as a high efficiency single band half-wave endfed antenna by many radio amateurs over a long period, but it was more or less forgotten when most radio amateurs started using coax-fed dipoles. 

In 2000, Frank, DL7AQT, did lots of experiments with the Fuchs, and was happy to end up with a multiband version for portable use.

QRPproject  sell an obtmized version of the tuner in a kit, it is based on Franks’ design with
some small modifications we made because the variable used by Frank is no longer available.

The antenna is a monoband endfeed half wave dipole. The length of the antenna should be a λ/2 or a multiple of it.

For 3.5 MHz you need about 41 m. But you can match these wire length with Frank's development also on all others bands between 10 and 80 m! 

The length of about 41 m is a good compromise. With the Fuchs circuit it is possible to use these 41 m wire on all bands between 10 and 80 m.

The alternative is 21 meters of wire for the bands from 10 meters to 40 meters

Having all the necessary parts on my junkbox I've assemble my version the only different parts is the variable capacitor, mine has a maximum value of 160 pf.

First tests are really encouraging, I was able to tune a 10 meters radial laid on the floor from 80 to 15 meters.

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