[Elecraft] K@ DSP Audio Filter Product Suggestion

[Lyle Johnson]

Hello Fred!

> ...  When setting up the audio filters, I would
> like to be able to select GAIN settings for each filter 
> bandwidth...
> If I could have different Gain settings for each filter
> bandwidth, then I could set up a variable CW PEAKING filter
> that could have progressively higher Gain for progressively
> lower bandwidth. This would allow me to take a small slice 
> of the band and amplify the signal for really....really weak
> signals!!!

This is an interesting idea.

A potential problem is that the KDSP2 is not really intended to provide 
gain in the normal sense of amplification.  The gain adjustments are 
intended solely to to provide equalization, so the apparent insertion 
loss of the KDSP2 should be about 0 dB.

Here's why.

The input analog-to-digital converter has a certain maximum voltage that 
it can accept from the product detector in the K2.  The output 
digital-to-analog converter has the same voltage limit.  If you apply 
too much internal gain in the DSP to a weak signal, and a strong signal 
comes in, you may overdrive the digital-to-analog converter, resulting 
in loud and unpleasant distortion.

The K2 AGC normally mitigates this by limiting the input signal to the 
analog-to-digital converter, but some operators turn the AGC off.  With 
the AGC off, the risk of unpleasant acoustic consequences increases!

Thus, I recommended setting the gains solely for equalization.  As you 
narrow the DSP, just turn up the AF gain control on the K2 :-)

Enjoy!

Lyle KK7P