On Tue, Oct 13, 2015 at 8:26 PM, Stephen Hicks, N5AC <steve@flexradio.com>
wrote:
>
> The only AGC that exists is to map the total dynamic range (in excess of
> 100dB) into the available "comfortable" dynamic range of your ear (the ear
> has a total dynamic range of something around 130dB, but for comfortable
> listening we assume something in the order of 40dB. It is not comfortable
> to strain to hear a weak signal at the bottom volume level only to have a
> strong signal blow your earphones off).
This is a slight skew in topic but wanted to make a quick comment on the
dynamic range figure Steve. I hope the Flex 6K AGC provides
configurability for the user to exceed 40dB audio dynamic range if desired.
Back in 2006, there was much interest in understanding why some receivers
seemed to homogenize multiple signals in a calling pileup (use case: you're
calling CQ in a contest or on a dxpedition and many are responding on
frequency). K3NA in particular published article(s) promoting a technique
to use highly isolating headphones to drastically lower the audio noise
floor, together with high dynamic range receiver audio to provide the
greatest perceived amplitude difference between weaker and stronger calling
stations. The idea was to have the band noise/weakest signals close to the
hearing threshold and the strongest signals right below the ear's
attenuation reflex level. I believe the resulting dynamic range that was
targeted was approximately 60dB. Several contesters implemented K3NA's
technique with good results and improved pileup readability. But my main
point here is that a high end xcvr vendor should hopefully not hamstring
the receiver AGC with a lower dynamic range and prevent such techniques.
Thanks for listening & 73,
Barry N1EU
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