RE: [Discuss-gnuradio] GNU Radio 0.3 Released

[Ettus, Matt]

> This release includes Matt's new SCA FM demodulation,

If anyone can find an audio SCA station and tell me if it sounds ok, it sure
would help out a lot.  I can't find any.  Or if anyone has a small FM
transmitter which can generate SCA, and could lend it to me for a few days,
that would solve it.

hifi_fm also has deemphasis on the FM audio.  It sounds muffled to me, but
the spectra look right.  I have a very bad ear for these types of things, so
if someone could try it out and let me know what they think, it would be
appreciated.

There's also a big DC frequency-offset term (that should be removed) which
is emphasized by the deemphasis filter.  Removing that will compromise on
the bass response a little, and allow for more gain.  This could be the
cause of the muffled sound.

Next step is stereo.  Then RDS.

Matt

P.S.  I know most people don't have the MC4020 board, so are mostly limited
to soundcards.  There's still a lot you can do -- stereo soundcards (in IQ
mode) could handle 45 kHz wide channels using 48k complex samples per sec.
The Midiman delta 44/66 could do two 90kHz wide channels or 4 45kHz wide
channels since its 96Khz/4 channel/24bits.  That would cover the entire
weak-signal portion of each HAM band, and significant portions of the FM and
HF bands.  The Delta 44 should be available for less than $200.

We'd need to add ALSA support for the Delta 44/66, but should anyway, since
that is going to be the new sound driver in kernel 2.6/3.0.  So if someone
has ALSA experience, that would be quite a good way to help out.  I have a
Delta 66, but no ALSA experience, so I could help if someone were to get it
started.