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Old January 31st 06, 10:14 PM posted to rec.radio.amateur.antenna
hasan schiers
 
Posts: n/a
Default Why did this work (160m antenna)?

Necessity being the mother of invention, bit me. Last weekend was CQWW CW on
160m. I stumbled on it and had no 160m antenna. I have a terrific performer
for 80m, an inverted L with 33, 60' radials stapled on the ground. I also
have a Carolina Windom 80 at 42' fed with perhaps 100' of RG8x.

Since it was a cw contest, I figured, brute force stuff with my tuner. Very
interesting results.

I tried the 80m inverted L, feeding just the center conductor, and also
tying the shield and center conductor together ...both cases feeding it as
an end fed wire. I got no band noise and very poor signals, but what the
heck, I worked 10 or 15 stations who were running S7 or better in spite of
things. I could tell I wasn't being heard very well. (I was also running
about 500w output).

Then I tried the same trick with the CW-80. I fed the center conductor
only...band noise jumped up to S-3, signals were amazingly loud, and I
started working everyone I could hear...first call. It didn't matter how
weak they were, I got answered immediately. I worked 44 states, France, and
two stations in Bermuda. My question: What is this antenna configuration and
why is it working so well, especially relatively low angle stuff like France
and Bermuda, West Coast, etc. I don't get it? (Feeding both shield and
center tied together, or feeding it "normally" did not work as well as just
feeding the center conductor)

This is an OCF Dipole, 85' on one side and 51' on the other. I have no idea
which side of the dipole was fed by the center conductor of the coax. My
coax runs underground (5' below the ground for 55' to the tower base), and
then up parallel to the tower (5 feet from the tower) for the 40' or so the
CW-80 is in the air). This really shouldn't work very well, yet it does.
VSWR bandwidth seems consistent with a somewhat efficient antenna (about 40
Khz before having to re-tune the tuner.

I'm at a loss to explain why it would seem to work so well as a DX antenna
for 160m. Pleased, but surprised. Any theories?

Am I somehow shunt/gamma feeding my tower?

I also had no tuner arcing, no rf in the shack, no RFI in the hi-fi,
.....zippo...all the RF appears to go where I would like it to, but I have NO
idea why. I prefer to understand things and not just rejoice in my dumb
luck. Ideas?

....hasan, N0AN