wrapping ssb antenna on kevlar backstay
 

Bruce in Alaska wrote in
:

day. A good compromise would seem to be a resonate 1/4 Wave at say
3200 Khz would allow for far efficency at 2182 Khz, by wrapping the
helical windings tighter at the top of the antenna, give a reasonable
length of wire on the lower part to resonate with the tuner at 12 Mhz,
16 Mhz, and 22 Mhz.

Bruce in alaska

I like the idea of the Kevlar as an insulator. But, instead of making it
into some kind of untuned RF choke, why don't we make it into a TRAP SLOPER
vertical by putting traps on the Kevlar, interconnected by straight
conductors, for the upper bands, above the natural resonant length of the
whole distance from feedpoint to mast, THEN use the tuner when the length
of the backstay becomes too short.

The coils in the traps will lower the natural resonant frequency below a
straight backstay. The trap capacitors are too small to be significant at
the low frequency bands. Below the natural resonance, the traps act like
loading coils for the tuner, drawing more antenna CURRENT up the too-short
radiator, which is never bad for good radiation.

On any marine or ham band the traps are set up for, no tuner will be
required and a resonant antenna is always a better radiator than this
stupid old marine base-loaded clothes line or flagpole we're using, now.

Larry
Above 40 meters, you could leave the lossy tuner in THRU....(c;

wrapping ssb antenna on kevlar backstay
 

In article ,
engsol wrote:

Oh boy..here we go...laughing.... see below....


snipped for brevity

Bruce has an excellent point re the windings...but I see a problem.
Given a kelvar backstay length, how would one compute the
pitch of the wrap? A turn every 6 inches for the first 2/3rds? Then
every 2-3 inches for the remainder? Ouiji board?

This topic is so interesting to me that short of buying a network analyzer,
(I'll be honest, I can't afford one), I'm determined to figure out what
simple test equipment I can use to evaluate various configurations,
and then test them.
Any ideas?
Norm B


Actually most of the work in this area was done by Ed Zanbergen, while
he was Principal Partner and Chief Engineer of MORAD Electronics in
Seattle, Wa. MORAD antennas are the defacto standard for commercial
vessels in the North Pacific. They build some of the most rugged and
effective antennas in the Marine Mobile Radio Service. Ed is long since
gone to the Great Radioroom in the Sky, but his legacy is still around
and being produced by MORAD today. When I was a beginner in this bizz,
I worked for Northern Radio Co. which had a shop next door to Morad,
and Ed and I became very good friends. I still have some custom antennas
that he built for me, specifically for MF/HF Coast Station installations
in alaska. I don't know if any of his notes were ever published, but
he spent 40 years designing antennas in these Radio Services.

One of the better designs that Ed built for me was a pair of matched
Helically Loaded Whips that were resonate at 3300Khz. I mounted them at
60 Ft in a Dipole configuration, with PhosBronze feedwire, connected at
the end of the 15 Ft Base tubes. Then feeding down to an Experimental
SEA 1612B Autotuner that has twin tuning boards driven by a single CPU/
Sensor System, so that both dipole legs are effectivly tuned by the
autotuner. This antenna can be heard, evey summer on the Marine Freqs
as KWO-70/WDT-59 and operations on all Marine Bands from 2003Khz
to 25 Mhz.

Bruce in alaska
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