[CQ-Contest] 10/15 interaction
Randall K Martin
rkmassoc at comcast.net
Thu Nov 6 10:18:35 EST 2014
Over the years, I've managed to clean up most of the cross band
interference that occurs when I operate my SO2R station running high
power. The one exception is that I cannot use my 10M monobander to
transmit while receiving on my 15M monobander. This is not surprising,
since they are only separated vertically by about 8 feet. Transmitting
on 10M must be dumping significant power back into the 15M transmitter
(an elecraft K-3) since it causes the COR relays to click and I get the
"HI RFI" error. When this happens, I immediately stop transmitting and
flip the 15M rig over to a tribander on a second tower. Normally, I'm
able to remember not to do this, but in the heat of a contest, I forget.
What I find odd is that I can transmit on the 15M monobander while the
second radio is connected to the 10M monobander and there is no "HI RFI"
problem. In fact, very little interference.
Here's my question. I'm contemplating purchasing a high power band pass
filter (4O3A) to prevent the interaction. I'd prefer not to buy both a
10M and a 15M filter if I don't have to. My intuition tells me that I
should be able to add the filter to the 10M transmitter. Any thoughts on
this? Is there some other path in which the RF could be reaching the 15M
rig that would render the band pass filters ineffective?
I have dunestar 100W band pass filters on both rigs, placed between the
rig and the amp. I know that adding separation between the monobanders
would help, but my tower configuration isn't really amenable to adding
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