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[VHFcontesting] Antenna Coupling Issues

To: "VHF Contesting Reflector" <vhfcontesting@contesting.com>, <vhf@w6yx.stanford.edu>
Subject: [VHFcontesting] Antenna Coupling Issues
From: "Les Rayburn" <les@highnoonfilm.com>
Reply-to: Les Rayburn <les@highnoonfilm.com>
Date: Fri, 11 Jul 2008 08:48:07 -0500
List-post: <vhfcontesting@contesting.com">mailto:vhfcontesting@contesting.com>
Some local VHF'ers have raised a concern about the proximity of my various V/U 
antennas mounted inside my attic. I have a total of five antennas mounted on a 
single 11 foot mast. The arrangement is very similar to the typical rover 
setup. Their speculation is that I should be careful about adding any 
additional TX power, as strong signals might damage pre-amps and/or the front 
ends of the various transceivers. 

I lack any sophisticated measuring equipment to accurately gauge the exact 
extent of coupling. SWR-wise, there is little to no interaction between the 
antennas, and it possible to operate both 6 & 2 Meters at the same time without 
any interference. 

Currently, I'm running 100 watts or less on each of the bands. But have newly 
purchased amps for 2 Meters and 432 that would take those bands up to 200 watts 
on 2 Meters and 300 watts on 432. 

I know this is asking a lot of generalities, when specifics would be needed to 
be certain, but here are my questions: 

1. At what power levels (typically) does this begin to be an issue? 

2. Are there steps that I can take to minimize the coupling, and protect the 
pre-amps and radios?

3. What do rovers in similar situations do to prevent problems?

As always, I'm in debt to those of you who are so willing to share their 
experience. Thanks!

73,

Les Rayburn, N1LF




Les Rayburn, director
High Noon Film
100 Centerview Drive Suite 111
Birmingham, AL 35216-3748 
205.824.8930
205.824.8960 fax
205.253.4867 cell
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