New antenna at ON7YD
Fri, 14 Aug 1998 06:40:52 -0400
Rik Strobbe wrote:
> >From Rik, ON7YD :
> Yesterday I got my new LF antenna ready. With the previous one I had problems
> with breaking wires all the time, for some reason (Murphy ?) the trees im my
> garden always move in opposite directions when it is windy ...
> The new antenna is a more conventional 'T', vertical part is 11.5 meter, the
> horizontal part is 4 parallel wires of each 21 meter long and spaced 0.8
> meter. The new antenna is also little furher away from the trees, the old one
> was partially hanging over some smaller trees.
> Last night I just connected the loading coil and 'tuned up', no detailed
> measurents done on the antenna. I can get 0.52 Amps antennacurrent (vs. 0.37
> Amps in the old antenna), so that is already an improvement. Since I need
> less inductance in the loading coil the topload should be better.
> TX output power is about 60 Watt (estimated from 85 Watt input and an
> efficiency of 70%), but a new 400 Watt PA is in the pipeline.
> Quick calculations give the new system an ERP of about 10mW and a loss
> resistance of 220 Ohm (was 4.5mW and 270 Ohm with the old antenna).
> 73, Rik ON7YD