Updated NBFM Recorder

Hi all,

I updated my multi-channel, narrow-band FM recorder, tested with B200
and
N210, and put it on GitHub.

https://github.com/madengr/nbfm_rec

Features:

Parallel demodulation and recording of NBFM radio channels
Up to N channels limited by CPU and bandwidth of SDR (tested to 25 

MHz)
Squelched audio blocked from recording
Mixed audio for real-time monitoring
Channels recorded to individual *.wav files

Tested with:

GNU Radio 3.7
Ettus N210 + WBX
Ettus B200

Lou
KD4HSO


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On Sat, Jun 14, 2014 at 8:23 PM, madengr [email protected] wrote:

Up to N channels limited by CPU and bandwidth of SDR (tested to 25 MHz)

Lou
KD4HSO

Nice work.

I recommend seeing if you can replace the bank for xlating_fir_filters
with
a pfb_channelizer_ccf block. This should be more computationally
efficient
than all of the xlating filters, so I’d really like to see if that’s
true
for you app.

Tom

I actually started with that, but the US 2 meter “suggested” channels
are
either 15 kHz or 20 kHz spacing depending on location. It’s interesting
to
dump all the 2 meter repeater traffic in my city to disk for several
days.
Even the busy ones are only active about 2 hours/day. Unfortunately the
800
MHz public saftey band is so wide it’s difficult to capture many
channels,
and they are P25 anyway. I patched in the DSD P25 decoder, but it can
only
handle two channels simultaneously. The public safety channel spacing
may
work well with the pfb_channelizer.

Thanks,
Lou
KD4SHO

Tom R.-2 wrote


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On Sun, Jun 15, 2014 at 12:28 PM, madengr [email protected] wrote:

Thanks,
Lou
KD4SHO

Gotcha. That makes sense. Thanks for the explanation.

There are ways to handle this situation of non-equal bandwidths, but I’d
wonder if it’s more complicated for this project than it’s worth (using
the
concept of the reconstruction filters). Could be a good testing ground,
though, to build a system that channelizes the entire band, does some
signal detection for those channels that are active, figures out their
channel bandwidth, and pulls them out or reconstructs them as necessary.
It’s a pretty advanced use of the PFB channelizers, though, so it’s not
a
trivial experiment to just run.

Nice work!

Tom

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