Topband: Improving the performance of a subpar vertical

Tom Rauch w8ji at
Mon Oct 24 21:13:43 EDT 2005

> Adding two more radials causes very large changes in
> the impedance of the overall system, as measured at
> the base. The R component went from 58 ohms to 105
> ohms (Can't remember the X, it was raining and getting
> dark quickly). I was incredulous, checked all of my
> connections, and sure enough, 58 to 108 (verified by
> disconnecting, measuring, reconnecting).  Presents
> about 1.8:1 before tuner.

Four radials .02 wavelength above ground does not make a
good  groundplane.

When the radials are .5 wave above ground it is an almost
perfect counterpoise (except for common mode current issues
on the shield and some pattern distortion from radial
radiation), but when the radial is 100 feet long and ten
feet high it is pretty tightly coupled to all that lossy

Weird interactions with soil shouldn't be a surprise.

73 Tom

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