> >From what I've read, the characteristics of WD-1x may vary quite a bit.
> It's interesting to read the results of the comparison that Herb did
> between some and open wire line back in 2008:
> http://lists.contesting.com/_topband/2008-12/msg00016.html
>From that link:
<<< In theory two parallel 600 foot Beverages even 65 feet
apart should allow some additional enhancement if fed properly.>>>
Only if staggered to allow end-fire. The myth close-spaced Beverages (or any
antenna) fed broadside have any advantage is easily debunked once we look at
how and why antennas work for receiving. We have to approach 1/2-wave
spacing broadside before pattern changes become worthwhile.
End-fire allows close-spaced improvements, but not broadside.
> As for low velocity factor, I think maybe that can actually help you if
> you
> don't have room for a full-size Beverage.
A reduced velocity factor can help, but it is very limited. Kraus covers
this in Thin Linear Antennas near the end of the chapter. The problem is
delay can tilt the pattern forward, but the effect is limited and can never
align response with the antenna axis. For a half-wave, HPBW from a veloctiy
factor of 1 is 60 degrees and 25 degrees off broadside. Slowing velocity to
.6 changes HPBW from 60 degrees to 51 degrees, and makes the main lobe angle
40 degrees from broadside in a half-wave.
I had some data when I worked with slow-wave structures, but the method paid
such small rewards I abandoned it. Using a multiple small inductors in
series works just as well as a helix, and can be mechanically superior.
Shunt capacitance to ground would also work, which is really what the
dielectric increases, but is very difficult to accomplish in any meaningful
amount in real life on 160.
All in all, it the insulation doesn't matter much in antenna mode. It
matters far more in transmission line mode.
73 Tom
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