Topband: parallel wire verticals
Fri, 25 Oct 2002 18:12:47 -0500
Subject: Topband: parallel wire verticals
> I've been considering building a BC Trapper (the
> wire version of the Battle Creek Special) But I got
> to wondering if I could skip the traps and run three
> wires in parallel with a single feed instead ... The
> 40m element would be completely vertical the 80 and
> 160 elements would end up as inverted L's.
> Any thoughts ? what kind of spacing would be best
I tried this 30 years ago on 20 and 15. Maybe it would work the same way
At the time, I was in northern Thailand where available materials were very
limited. My house had a sheet metal roof which made a terrific
counterpoise. I tried cutting the two verticals to formula length. The one
for 20 worked just fine; on 15, the frequency was way off. I think it was
electrically longer. One of the few materials I had was scraps of coax. I
put a long piece of coax in series with the 15 meter element as a series
stub and cut off a few inches at a time until it resonated. Both bands then
worked fine. However, I was not using an amplifier and I suspect that the
coax dielectric (RG-59) would have melted at higher power. A vacuum
variable might be required to withstand the high rf voltage. It's the same
problem as feeding a gamma match on a shunt fed tower.
As for separation, I guess they were maybe 5 degrees apart.