I have no dedicated WARC antennas, except a pseudo-vertical on 10 MHz (used
aluminium that was too soft!). Here are my findings; nothing measured or
concrete, just that "it works".
I force-feed the C3 on 12 and 17, and also occasionally on 30. It's mounted
at about 17 m (50'). SWR is around 4:1, 1,8:1 and 3:1 respectively.
There's very little F/B on 12 and 30, but probably around 10 dB on 17. I
normally use the amplifier (2 x 3-500Z, GG) as an Active Antenna Tuner, and
make sure that the grid current is in limits.
It works well enough. Comparisons with a Cushcraft A3WS showed little
difference on 12 and 17. It is several dB worse than the vertical on 30,
although it sometimes hears better (polarisation, I guess). I've never had
a situation when it was a better transmit antenna than the vertical on 30.
Given that I'm a contester, and only occasionally play some DX on the WARC
bands, it does everything I need on the WARC bands. I have an average of
over 250 countries on each band, with very limited operating.
One caveat: With the severe mismatches that you'll see, you need to think
carefully about the choice of balun. If you use a ferrite core transformer,
you will come to grief. I use a simple coax choke (about a dozen turns of
RG213), and it hasn't failed in almost five years of usage. A friend used a
commercial balun with his C3, and blew it up in short order.
Short version: It works, if you can handle the SWR and you don't use a
fancy balun.
Chris R. Burger
ZS6EZ
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