Topband: elevated vs buried radials

[Michael Sapp]

Hello Bill (W4ZV) and Group:

Bill wrote: > For some
reason K3LC did not model the 2 elevated radial case
but it would have been interesting to have seen that.

        That would be interesting for me as well. I use a short top loaded 
ground plane antenna
on 160m (MFJ-1793) with two 1/8 wave radials and two 1/16 wave radials up
15 feet. An LC parallel trap provides
160m resonance at the base of the antenna. One observation I would like to
contribute is that changes in ground resistance are very noticeable  on
this antenna. The annual rain fall last year was 30 inches above normal and
several times after heavy rains the
antenna resonance shifted 40 to 50 KHz down in frequency. As the ground
water slowly drained off the antenna resonance
would drift back to its original value. The last few snow-freeze-melt
cycles here the resonance point moved about 30 to 35 Khz
between frozen ground and snow versus thawed-wet ground. Fortunately my
base LC network is adjustable, else the resonance
shift would put the 1:1 match below 1.800 MHz.  Yet on 80 meters, I see
little or no resonance shift with varying ground moisture content. 
The shortness of these elevated radials may be part of the cause of the
resonance shift.  Even so, I can't imagine trying to get a 
phased array working in this situation. On occassions I've been able to
work EU stations with 100W on cw, so the antenna does
work reasonably well for its small size. But without feedpoint tuning it
would not be very practical.

                                                        Mike WA3TTS