Esteemed reflectees:
I missed some of this when the local server was down. Forgive if
some is a repeat, but I thought my experience along this line might be of
interest.
For 2 160 seasons I used a 1/4 sloper of #12 wire, fed 73 feet up
my tower. The tower has 9 guys and no insulators. The desert ground here is
rotten to worse, depending if any moisture came thru. I replaced the wire
with 450-ohn ladder line, installed as one conductor of broad cross section
(ie the ends soldered together) After pruning for the change in L/D vice
the single wire, I got an increased bandwidth (at 2:1 points) of about 65
kHz. With my mighty 100w and no Beverages, this is the best system I have
come up with. The Zo is low, maybe 18 ohms, and I have no figure for the
ground loss.
Anyway, I worked some of the top EU guys with the better ears, but
with difficulty.
Last year I read an old handbook, and in it I saw the "twinlead
Marconi", using 300 ohm line and fed against a counterpoise or good screen.
Realizing a good thing here, I installed one made from the 450 ladder line
(all I had) and put the feed up on the tower where the sloper was; so now
it is an "inverted twinlead Marconi". Anyway, the Zo went up to near 65
ohms, and the 2:1 SWR points went to 30 khz wide. BUT... the increase in
performance, as reflected in the better DX results was striking. No
question it inproved things, IMO.
I was later able to borrow a 400w amp, and was then able to
(almost) compete in the piles with the buch better-equipped stations, and
worked the 9X, V51, and ZS4TX with ease (big thrill in this, thanks
gentlemen!) But with 100w there was no question it worked better.
BTW, I know of no one using this antenna, and have heard no one
speak of it. Whether or not the math stands up is academic to me, as
everyone knows the bumblebee can not fly...the proof of the pudding is in
the eating, as it were. Anyway, I made no other changes in the system other
than the antenna. Same placement, same (lack of) moisture, etc. The
improved results came with the change.
I tried going back to the old #12 wire sloper, and the results went
back to poor. Tried the 450 line fed as one conductor, got the same BW
improvement but nothing noticable in the performance. Put the Marconi back
up, and I got the better results immediately.
Since I have never seen this arrangement written up in any
publication, nor heard of anyone using the idea, I'd like to hear from
anyone that has. And also from anyone that may try it.
73 de Jim, KF7E
"May the Flux Be With You."
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