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Re: Topband: Flags and loops in restricted space

To: <topband@contesting.com>
Subject: Re: Topband: Flags and loops in restricted space
From: Björn Mohr <bm@broadcast.se>
Date: Sun, 30 Dec 2007 03:25:41 +0100
List-post: <mailto:topband@contesting.com>
Thanks Carlos,

Lots of useful information here;

> You can have any non resonant antenna close to each other, like several 
> EWE's or Flags, they are the same class no resonant antenna.

My RX antennas are non-resonant, except for the 20ft coax loop. This seems
to be the good news. Terry N6RY pointed out that modelling these antennas
show very little interaction. 

The TX antenna is located about 50-75 meter away from the RX antennas and I
am not sure if I would gain anything by detuning it. What is the simplest
way to find out?

> Common mode noise is very important to keep it very low, RF chokes and
good 
> ground is very important to receive only the signal from your RX antenna, 
> Beverage, EWE or flag and not from the feed line, the external cable coax 
> shield can pick up a lot of signals too. 

I find this interesting. My coax picks up a lot! It is laying on the ground
running parallel with coax and rotor cables from the tower, so I need to
clean this up. Again, I don't have much space to occupy... How far would I
have to separate cables to reduce common mode noise? I can't bury the coax
as the terrain is all rock. What other actions should I consider?

73 de Björn /SM0MDG (7S0X in SP contest)


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