[Elecraft] Elecraft technology >> K2+

[Lyle Johnson]

Hello Charles!

> Say, did any of you guys look at the audio spectrum of the DSP NR audio
> using Spectrogram?  It's pretty weird, and I need someone to explain what
> is actually going on.

The KDSP2 uses an adaptive LMS algorithm.  This is DSP-speak to say that it
is adjusting an audio filter.  When it sees what it thinks is noise, it
tires to suppress it, and because noise is spread out over the whole audio
spectrum, you will see what looks like a "comb" effect of a number of
filters.  Maybe "lumpy" is a better description of the resulting passband
when there is only noise.

As signals appear, the filter elements adjust to try and pass the signal
content, so you'll see the response peak up on the signals.  Since voice is
a complex waveform, the filter adjusts itself to pass the part of the voice
response that it thinks is a signal, and to continue to try and suppress the
frequencies that it thinks are noise.  The resulting audio characteristic is
somewhat "hollow" sounding.

73,

Lyle KK7P