[Elecraft] K3 pwr out on digimodes

[Julian, G4ILO]

Joe Subich, W4TV-4 wrote:
> 
> 
> the purpose of ALC is not to control the 
> shape of the passband across the SSB filter it is to prevent a 
> SSB signal in total from overdriving the power amplifiers.
> 
> 

I agree with you. As applied to a voice SSB signal or even a wideband data
mode that is completely correct.

But in practise with a narrowband signal like PSK31 the effect will be to
keep the output RF at the same power, whatever audio frequency the signal is
being generated at, because only a narrow band of frequencies is being used
at any one time.

If the filter response varies across the passband, which it does, the ALC
will vary the amount of gain used to try to keep the RF level to the amount
it is set at, whether the signal is being generated near the edge of the
passband or at the center. This is important to the PSK31 operator who does
not want to tune every signal to the center of the passband sweet spot
before hitting TX in order to get maximum power out.

-----
Julian, G4ILO. K2 #392  K3 #222.
http://www.g4ilo.com/ G4ILO's Shack   http://www.ham-directory.com/ Ham
Directory    http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3 
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