[Elecraft] K2 with DSP, big NO NO!

[James R. Duffey]

Daniel - I disagree with you that the DSP is not needed or useful with
Elecraft radios. The frequency response of a series of circuits, such as
comprise a receiver, is the frequency response of each individual unit
concatinated together, assuming that each unit is linear.

So, if the DSP has a better frequency response than the circuits that
preceed it, the frequency of the whole will be improved by the addition of a
DSP. Again, assuming all the circuits are operating in a linear region. For
the K-2 with AGC off this is a good assumption under most operating
conditions. In fact, since the K-2 is less subject to the non linear effects
of second and third order intermodulation, a good DSP unit will be more
useful with it than with other receivers.

I do not have a K-2, but I do have a K-1, and have played around with it a
good deal on a spectrum analyzer with various audio filters. The frequency
response of the K-1 has a very gentle slope on the high side and, on the
wide settings  is somewhat ragged to boot. Rod, N0RC, had some  good
spectrograms on his web site that demonstrate this quite vividly. I think
the extraneous bumps on the high side are due to IMD in the audio output. An
audio filter, either analog or DSP cleans these up very nicely, and makes a
dramatic difference both to the ear and the spectrum analyzer.

Your mileage may vary, but a good audio filter is a useful adjunct to nearly
every receiver, assuming, of course, that good narrow IF filters have
already been fitted. Selectivity early in the receive chain is preferable
due to potential non linearity problems. But if the early stages have been
taken care of, audio filters can be of great utility. - Dr. Megacycle
KK6MC/5
______________________
James R. Duffey KK6MC/5
Cedar Crest NM 87009 DM65