Topband: Good or bad conductivity

K4SAV RadioIR at
Sun Apr 26 08:12:24 PDT 2009

allan1 wrote:
> I've got all the materials for an 160/80 EWE including a commercial 3:1 matching xmfr with pre-amp which I am thinking of installing.  My soil is red clay.  Will this soil's conductivity make for a good rcvg ant or a poor one? ........

Here in Alabama we have real red clay.  It turns to slippery goo when it 
gets saturated with water, and turns to pottery in the summer.  Even 
though it has a lot of iron content, it isn't very conductive (at least 
near the surface).  An EWE will work fine, but I would recommend an 
eight ft ground rod at each end.  I tried four ft ones and it worked OK 
with a 4 element EWE (two element used at a time), but it worked better 
when I changed to eight ft ones.

When you analyze this you will find that a very good ground is not 
needed for the EWE, however a 4 element version is a lot pickier than a 
two element one, and is dependent on both elements being matched.  A 
poor ground (greater than about 200 ohms) makes that more difficult.  A 
poor ground usually results in some loss of forward gain and some loss 
of front-to-back.   With a single element EWE you can juggle the 
termination resistor and get that F/B back even with a poor ground but 
things are difficult to control with a poor ground.  Each direction may 
be different, small changes like rain may make a difference, and the 
effect is different at different frequencies.  So if you have a ground 
that is 100 ohms or less, things are a lot more controllable.

A three to 1 transformer isn't a very good match for the feedpoint 
impedance of the EWE.  Normally for 50 ohm lines you need about a 12 
to1, and for 75 ohm lines you need about 8 or 9 to 1.  However with a 
transformer/preamp it may work OK if it has enough gain and it is 
located at the EWE.  Also the preamp needs to have very good intermod 
characteristics.  Local AM stations put out some pretty strong signals 
and short wave broadcasts stations can be a problem too because the gain 
of the loop increases by maybe 25 dB for those stations.

Jerry, K4SAV

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