TopBand: 160m shunt feeds

[Robert Kile]

In response to questions.

I use short aligator clip lead with 1-2 turns on GDO coil to find the
1/4 wave resonance which is the lowest frequency that you will get dip
in meter.

With trial and error methodology I choose natural resonant frequency of
1-1.2 Mhz because the feedpoint attachment point will +Xj + R and the
series capacitor at the feed point will be 200-300 pf range to give
impedance of 50 Ohms (R + -Xc).

Models show some gain. However, the losses in ground return will negate
this. The take off angle without optimum ground system will be in 25-30
degree range. For my application in the city the current distribution
will be higher above the ground and I'll have low loss matching. One
values are determined I install fixed capacitors and either use parallel
heavy drop wires in cage or 1" tubing to cross arm point.

Admittedly feeding a grounded top loaded tower against real earth
involves a bit of Voodoo Black Magic!

73

Bob KG7D

--
GIF89aI!



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