Al:
I had asked a similar question of this reflector a few years ago when I
was considering installing mast-mounted pre-amps for V/UHF Yagis above my
tribander. I was concerned about HF RF frying the V/UHF front ends.
It was suggested to me that I install a power meter with appropriate
slugs in the V/UHF Yagis' feedlines and transmit on HF. I could then
measure the actual power coupled into the V/UHF array(s). Maybe this
technique would work for your situation. I don't see why not.
Once you know the magnitude of the coupled energy from one HF band into
another, you can decide whether additional isolation or filtering measures
would be necessary.
73 de
Gene Smar AD3F
----- Original Message -----
From: "Al Williams" <alwilliams@olywa.net>
To: <towertalk@contesting.com>
Sent: Saturday, March 19, 2005 12:11 AM
Subject: [TowerTalk] crosstalk between beams on a common boom (such as
c31xr)
> For example, transmitting on a 20 meter beam while listening on a 15 meter
beam.
>
> How great is the risk of damaging the front end of a receiver listening on
one beam while transmitting on a second beam
> when both are close spaced?
>
> I used EZNEC briefly and was surprised that a parasitic element of the
same dimension results in current in the parasitic
> almost as high as the driven element (for a spacing of about 4 feet)
.However, changing the parasitic length to another band
> dropped the current down to about 20 % of the driven element.
>
> But I don't have any idea of the relationship of current in the parasitic
element to that obtained when the parasitic element
> is actually the driven element on another beam. I tried putting a 50 ohm
load in the parasitic element and that dropped
> the parasitic element current even more.
>
> But, since the frequency of the signal on the 15 meter beam is 20 meters,
I presume that the SWR is high and a
> voltage amplification may result depending on the transmission line
length.
>
> BTW, I would be using Dunestar filters on both rigs, but am concerned
about inadvertently not having the filter turned
> on at some time.
>
> looking forward to explanations
>
> k7puc
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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