[CQ-Contest] Re: Choice of CW Narrow filters

Bud Hippisley k2kir at telenet.net
Fri Apr 16 17:18:48 EDT 1999

Well, there's a name for this effect, which has been documented
previously in other fields.  In my advanced years I can't remember it,
though.  The essence, as I recall, is that the "right" amount of
background noise can enhance your perception of the desired signal.
I, too, find it easier to pick weak CW signals out of the noise with
the 2 kHz SSB filters (stopped down to about 1.2 kHz with the VBT
control) than with the 500 Hz CW filters at full BW, but I've also
used the effect (and in fact first noticed it) when trying to analyze
a strange noise from the car while driving.  Turning on the radio and
having some background music actually enhanced my ability to hear the
alien noise from the engine compartment.  Talk to the psycho-acoustics
specialists -- they'll know the name of it!

Bud, K2KIR

At 11:07 AM 99/04/16 -0600, you wrote:
>n6tr at teleport.com wrote:
>> I recently discovered the power of this DSP when doing moonbounce
>> work on six meters.  I have always thought that you had to use really
>> narrow filters on your receiver to hear weak EME signals.  However,
>> what I found was that it was EASIER to copy weak EME signals using
>> the SSB bandwidth positions!
>I've observed the same thing on HF.  In the absence of strong QRM, a weak
>signal is just as easy, or easier, to copy with a wide bandwidth.  Since wide
>filter bandwidth clearly must reduce the S/N ratio, the effective bandwidth
>organic DSP must be much smaller.  Quite amazing.
>Scott  K9MA
>Scott Ellington
>sdelling at facstaff.wisc.edu
>Madison, Wisconsin    USA
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