[CQ-Contest] Need confidence....

[Jim Brown]

What radios and what separation?  What power level? Serious common mode 
chokes on each antenna at the feedpoint?  Some radios are a LOT better 
than others.

On our CQP county expeditions, we regularly run two  K3/KPA500 stations 
into two C3SS on the same band, one on CW and one on SSB, with spacing 
of about 200 ft, on 20, 15, and 10, and with no interference. The 
antennas are aimed to 70 degrees and are carefully placed with their 
driven elements co-linear. We've run two on 40 and two on 80 with 
dipoles separated by about 300 ft.

There's a review of multiple bandpass filter sets on my website, all of 
which are intended to run between the rig and the power amp.  SOME sort 
of harmonic suppression filter is needed on the output of power amps so 
that harmonically related CW stations don't wipe out the RX of the 
station on the higher band. Stubs work quite well for that.  See the 
piece on my website about that.

This doesn't answer your question about high power bandpass filters or 
triplexers, but there are other solutions, depending on your resources 
and the constraints imposed by your site.

Another point. Antennas resonant on a single band at a time inherently 
help with harmonic suppression because the antenna is badly mismatched 
to the feedline at the harmonic. For that reason, the small 2-el SteppIR 
is an awfully good choice. It's quite lightweight,and collapses rather 
well.

73, Jim K9YC

On Tue,10/4/2016 6:03 PM, Ray Day wrote:
>   to activate Santa Catalina
> Island (IOTA NA066) again in February 2017. In the past we've had problems
> with 2 radios simultaneously on 20/17, 17/15, 20/15, etc. We don't have the
> room to be completely "tip-to-tip" with our 2 hexes, nor can we get much
> physical separation between the 2 antennas for the 2 rigs. So - problems.