[TowerTalk] remote control of antenna switch via "wired" UHF

[Kelly Taylor]

Hi Pete,

It seems to me: you're attempting to couple both your two-way HF energy and
the UHF energy required for switching onto a common feedline, is that right?

It seems it would be doable, but the difficulty to me appears to be
isolating one from the other at both ends of the feedline. You don't want
your HF energy to fry the switch and I'm pretty sure it would be some kind
of rules violation to radiate that UHF energy through your antennas.

You probably are looking at some type of duplexer/diplexer arrangement,
where one port at the shack end accepts HF, the other accepts UHF and at the
switch end, only UHF comes out of one port and only HF comes out the other.

If you're running power, the question then becomes: is this cheaper than
just running another length of feedline?

Because both are RF, it seems more difficult to me than injecting DC (a la
RCS4). Perhaps if you built identical tuned circuits resonant at UHF, these
could couple/uncouple the UHF energy (appearing as an open circuit to HF)
and then put a low-pass filter north of the uncoupling circuit? Perhaps you
also need a low-pass filter south of the coupling circuit, I don't know.

Of course, the feedline is going to be just as lossy at UHF with the couple
HF/UHF signals as it would with just UHF, so you'd have to know that you're
getting enough UHF out the other end to work.

73, kelly
ve4xt

On 1/1/12 9:18 AM, "Pete Smith" <n4zr at contesting.com> wrote:

> I am planning to build, in the next couple of days, the couplers needed
> to test this idea.  To revisit it, I have qn inexpensive RF-controlled
> 8-way band switch, and several people suggested that I should couple the
> RF from the "remote" to my feedline, and pick it off the other end, to
> eliminate path losses over the ~300 foot range.
> 
> This seems plausible to me, but as usual I'm having trouble figuring out
> the specifics.  Say I take a piece of RG-59, remove the jacket and the
> shield braid, and then couple the output from the remote to the center
> conductor moni-match style.  Should I lay the coupling wire parallel to
> the center conductor, or should I wind it around the insulated center
> conductor?  What sort of total length for the coupling wire would give
> best results at ~315 MHz?  Any difference in the design of the coupler
> on the receiving end?
> 
> I assume I should pull the braid back over the "coupler" section - is
> that right?  If I have common mode chokes (#31 toroids) on both ends of
> the feedline, will it be better to have the couplers between the chokes,
> or doesn't it matter, since the UHF RF will presumably be going by
> differential mode?