[RTTY] G0MGX SARTG

[Don Hill AA5AU]

Mark, G0MGX wrote: 

>>>Some very bad and overdriven signals all over - 20M so packed at times,
filers in overdrive and still not able to cope.

I read this all the time and I admit that I do, on occasion, hear some
overdriven signals but not very many.  Maybe the problem is worse in Europe, I
don't know.  But I think I only heard two bad signals all weekend and only one
was on 20 meters.

I just wanted to comment that many times in the past I had thought that signals
were badly distorted and splattering on 20 meters when it got crowded only to
find out it was my receiver that was having the problem.  I experimented this
weekend on this very subject.  I tested the receiver on my IC-775DSP compared to
the receiver on my Kenwood TS-870 on 20 meters when it was crowded.

The receiver in the Icom seems to have much better sensitivity than the Kenwood,
but on the crowded 20 meter band this past weekend, the Kenwood with the AIP
function and IF Noise Reduction enabled, outperformed the Icom with its audio
noise reduction when it came to copying weak signals with adjacent strong
signals.  The Kenwood, with the AIP function turned off, had a hard time pulling
out the weak ones and at times made it sound like just about everyone with a
strong signal was splattering when they weren't.  Whereas the Icom held its own
and performs quite well under these conditions, but just not as good as the IF
DSP and AIP of the Kenwood.  Actually, I think the Icom has the overall better
receiver and now use it as my main radio outside of contesting.

Narrow filters do help in crowded band conditions (I ALWAYS leave my on 250 hz
filter in line - never turn it off during a contest except to check if there is
a nearby station), but there are other factors which can cause a receiver to
become overloaded.  One thing that can cause the receiver to become overloaded
is having the Noise Blanker turned on.  Always turn your Noise Blanker OFF in
crowded band conditions with strong signals.  The Noise Blanker will make it
sound like EVERYONE is distorted.

And another very valuable asset to my station is the JPS NIR-12 dual DSP audio
filters on each radio.  They are worth their weight in gold when it comes to
cleaning up audio before it ever reaches the sound card and headphones.

Again, I'm not saying there aren't stations overdriving their audio using AFSK
or that there aren't distorted signals, but I just don't hear very many of them
for some reason.  Another trick under crowded band condx is to use your radio's
attenuator.  I don't have to do this on 20 meters because the Kenwood is nearly
always my 20 meter radio and the AIP function acts similar to using an
attenuator.

Just some thoughts on the subject that came to me as I read Mark's comments.
Maybe these tips will help someone.

73, Don AA5AU