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[AMPS] True Or Not True #2

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Subject: [AMPS] True Or Not True #2
From: (Tom Rauch)
Date: Sat, 8 Sep 2001 15:35:07 -0400
> Many years ago, as weak-signal 2 meter CW was becoming popular,
> a chap (I forget his name/call) could copy a signal 2 db below the
> noise level. This was confirmed by testing him, and seemed to be the
> record at the time.
> (((73)))
> Phil, K5PC

Good CW ops can hear well below noise. It is common. -2dB is 
really not anything exceptional at all Phil.

I can clearly hear a tone and copy CW when the noise power is ten 
dB greater than the tone power, even when the bandwidth of the 
noise is restricted to 500Hz. It becomes more and more difficult 
however if the noise is "filtered" so it becomes more and more like 
a tone. I do very poorly with near unity S+N/N and 80Hz filters 
because noise power is concentrated on the same frequency as 
the desired tone.

That's why DSP filters were such a big hit for casual operators. I'd 
watch people oooh and aaaah when a filter was switched in on a 
demo tape, yet it made very little difference to me. The brain really 
can filter the CW with quite a narrow bandwidth.
73, Tom W8JI 

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