[CQ-Contest] SO2R Interstation Interference Issues

Martin Monsalvo - LU5DX lu5dx at lucg.com.ar
Tue Sep 6 09:15:39 EDT 2016

Hello Joe,

Your antenna setup looks pretty much the same as the one at LP1H in terms 
of antenna separation. Antennas are really close to each other. Specially 
10, 15 and 20 meters. (30 ft or less from each other).
40/80 and 160 are 100 ft away from the high bands, but very close to each 
other between themselves. (50 ft separating 40 and 80). The 160 m inverted 
V is placed at the top of the 40m tower, so there is only a few ft between 
All inter-station interference was over when we replaced the BP filters 
with the latest edition of 4O3A BP filters.
We use those at the output of the eight pack (also by 4O3A). This antenna 
switch exhibited better isolation than the six pack we were using before.
All in all, the new setup was tested during last year's CQ WW DX CW and 
No signs of RFI whatsoever, using any combination of bands.

Martin LU5DX

P.S. We didn't even have to connect the low power BPFs between the 
transceivers and the amps.

On Tue, Sep 06, 2016 at 8:50 AM, Joe Galicic < galicic at comcast.net 
[galicic at comcast.net] > wrote:
I am in the process of building a SO2R station and have a question of 
interstation interference and bandpass filters. I live on a very small lot 
and have no room for antenna separation. I only have wire antennas and a 
vertical for 20 meters. I have a set of bandpass filters for each radio. I 
still get quite a bit of phase noise hash on adjacent bands even with 
filters. It doesn't seem that the filters make any difference at all ? The 
biggest reduction in noise is between the dipole antennas and the vertical. 
Can I ever expect to get the noise to acceptable levels with antennas so 
close to each other ? Thanks -Joe N3HEE
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