[Elecraft] AGC Setting for PSK-31

[Joe Subich, W4TV]

> I can honestly say I have not noticed any 
> difference either on TX or RX in ordinary sound card 
> operation. 

With the K3 the Line Out level is sufficient for nearly any sound 
card as long as care is taken to avoid obvious wiring errors that 
would introduce noise.  However, with some rigs that have limited 
outputs (some early Kenwood transceivers or the K2 without the 
W3FPR modification) the signal level is in the noise floor of the 
soundcard.  

> Although the K3's receiver may have the dynamic range to 
> handle working with the AGC off I think you would increase 
> the risk of clipping or distortion somewhere in the audio 
> path that would result in "ghost" signals.

Without AGC the dynamic range at Line Out is sufficient to drive 
most soundcards into clipping with an S9 signal if the "no signal" 
noise floor is set 10 dB above the noise floor of the sound card. 
Some level of AGC (compression at S9 or above) is beneficial but 
can also result in blocking by strong signals in a wideband 
decode mode as you point out. 

73, 

   ... Joe, W4TV 
 

  

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Julian, G4ILO
> Sent: Thursday, January 22, 2009 5:40 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] AGC Setting for PSK-31
> 
> 
> 
> I recently purchased an SB Live 24 card to use for datamodes, 
> so I could use the built-in Realtek sound for normal computer 
> purposes. I can honestly say I have not noticed any 
> difference either on TX or RX in ordinary sound card 
> operation. I imagine there might be a benefit if I was using 
> it with an SDR (SoftRock, etc.) but I haven't tried that.
> 
> Although the K3's receiver may have the dynamic range to 
> handle working with the AGC off I think you would increase 
> the risk of clipping or distortion somewhere in the audio 
> path that would result in "ghost" signals. I prefer to 
> operate with AGC on and use the filtering to exclude other 
> signals that would affect the AGC to the detriment of the one 
> I am trying to copy.
> 
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack   
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