[Elecraft] KDSP2

[Lyle Johnson]

> Have been playing with the KDSP2 now for a few hours. I have found an
> additional perk with the DSP which really adds to the utility of this
> option. You can now increase the audio gain though the KDSP there by
> increasing the rigs audio output to a level much greater than through the
> stand alone K2.

Note that there is a danger to doing this.

It is possible to increase the gain so much that you hit limiting (clipping)
inside the DSP.  This is manifested as really loud, distorted signals.  If
you increase the gain through the filters and then switch AGC OFF, you might
get an unpleasant surprise.  Similarly if your AGC is somehow adjusted such
that really strong signals make it through, you might also get clipping in
the DSP.

The intent of the gain adjustments was to allow *balancing* of the audio
levels across the modes (CW, SSB and RTTY).

> In addition, you can adjust the audio gain of the denoiser
> to balance the audio output to the output without it engaged.

Yes.  This was made available for exactly this reason.  However, be aware
that cascading too much gain in the DSP to try to increase overall K2 system
gain might yield the same clipping problem mentioned above.

The level is adjustable because more aggressive denoising levels result in
greater loss of desired signal.

Finally, remember that different signals have different qualities from the
perspective of the denoiser.  A good example is to set the mode to SSB, tune
in an SSB signal with the denoiser and set the gain to make the signal
appear to be the same level with noise reduction on or off.

Then, tune to the 4 MHz test signal in your K2 with denoiser and notch OFF.
Turn the denoiser ON.  You'll hear a much louder heterodyne.  Continuous
tones have much better "autocorrelation" properties so the denoiser ignores
them pretty well.

This is also the reason that CW denoise has a separate gain adjustment than
SSB denoise.  And why the CW denoise default is 0.0 dB :-)

73,

Lyle KK7P