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

Justin Snow justin at g4tsh.demon.co.uk
Sat Apr 17 11:26:25 EDT 1999

I think this is what is called Stochastic Resonance.

At 21:18 16/04/99 , Bud Hippisley wrote:
>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
>>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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Justin Snow  G4TSH
justin at g4tsh.demon.co.uk

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