[CQ-Contest] WPX QRM - Time For A Re

Ken McCormack zl1aih at gmail.com
Tue Mar 29 01:56:11 PDT 2011

Hi Brian,

You wrote:
"Increased usage of amplifiers  is  the major part of the problem. On the
few occasions I dared to tune the band portion mentioned there were in fact
not that many contacts going on. There were some piles for dx stns but most
room was taken up by wide big signals de-sensing all other signals around
that area or splatter making adjacent
 frequencies unusable and an endless wall of noise from 21.200 to the 21.450
band edge. I think the problem is far worse in EU than any place else."

I listened to WPX SSB from time to time during the contest and heard the
splatter from many stations EU and US, some of which were 15kHz wide here in
ZL - BW 2.1kHZ, attenuator on, RF gain low, AGC off, K3 transceiver, 2-el
quads etc

The splatter from the most obnoxious signals was a nuisance but there was no
de-sense at all.   OTOH while working in the shack I monitored a S9+30dB
Multi-op Hawaiian station with a very clean signal running JA and Eastern
EU, while a strong VK4 was doing the same only 2kHz below with no problem to
either station.
I could hear the stations that they were working, armchair copy.

Increased use of amplifiers, whether commercial or "home-brew" is not the
major part of the problem - it is amplifiers over-driven by incorrectly
adjusted transceivers that is the 'major part of the problem'.

The minor part of the problem is incorrectly adjusted receivers - full RF
gain, AGC slow, not to mention wide-open front ends.   'Up-conversion' is
the design handicap for those manufacturers who must cater for a much wider
market than ham radio.

However, obnoxious signals will splatter, amplified or not.<G>

73, Ken ZL1AIH

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