PS: The PA is a H bridge, using 4x IRFP460A, switching directly at 320
VDC (230V AC mains voltage here).
73, Stefan
Am 26.09.2013 00:33, schrieb Stefan Schäfer:
Hi Bob,
Am 25.09.2013 21:13, schrieb Bob Raide:
Stefan;
The voltage is terrible! I can draw a 2.5 inch flame off the ant input.
I know hwat you mean. Similar problems here when i was setting up the
system here is 2011, see
https://dl.dropboxusercontent.com/u/19882028/LF/20111106-20h02m13s-FF7_8470.jpg
That was not even half the voltage i have to deal with now (a sphericas
electrode solved the problem,
https://dl.dropboxusercontent.com/u/19882028/LF/Electrode.JPG
).
More top loading would be great but also use this
ant
for 80 and 160 meters.
And what is the problem? It is not Lambda/4 for these bands so you need
a matching network anyway, don't you?
You are probably using a much bigger ant than what I
have here.
No, my antenna is smaller. It is an INV-L, 30m up and 70m long. The
effective height is 25m, about. The wire is 10mm diameter steel wire
(was designed to withstand a direct lightning strike). You see from the
image above that the isolator is quite heavy (takes 60 kN). 50 kV rms
in rain is no problem, however there are other regions where corona
discharges become visible, depending on the temperature and humidity.
What i do is keeping the earth losses extremely low! And i took RF litz
wire with 729 strands for the coil which has a Q of about 1000. Power
levels are rather moderate here, also because i'm running the TX all
the time when sleeping :-) You know, the best results to the west are
achieved at night!
73, Stefan/DK7FC, TXing WSPR-15 on LF again this night.
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