|From:||Darrin John Eden|
|Subject:||Re: [Discuss-gnuradio] cable modem tuner now integrated|
|Date:||Mon, 26 Nov 2001 01:15:20 +0100|
I've now got a very nice cable modem tuner module (eval board) hooked
into GNU Radio. From a hardware point of view it was a zero glue
operation. Just a couple of cables and rigging up a power supply.
FYI, it's a Microtune 4937DI5 3x7702 module. Tunes from 50M to 860M
and has about a 6MHz wide IF centered at 5.75M. Very convenient for
our 20M sample A/D board. Cables right up. You control it by bit
banging it over the parallel port. It has a I2C interface plus a few
I've attached some FFT graphs from various parts of the spectrum.
Lots of good stuff to work with. The center of the IF is indicated at
5.75MHz. The displayed frequency axis values don't currently take
into account where the module is tuned.
Here's what they are:
Lots of broadcast FM stations. Should be able to cook up a
cool demo that demods more than one station at a time without
retuning the RF front end. This will show something that you
can't do with a regular radio. Existing code demods the
channel that is tuned to 5.75M
Local TV channel 35. Should be able to extract the audio.
Not too exciting in the snap shot, but in real time there are
all kinds of signals coming and going. Some are conventional
push-to-talk FM, but some appear to be burst transmissions.
Narrow band FM. Note close channel spacing. Some are FM, some
Right hand side of graph is spread spectrum lump.
Conventional narrow band on left hand side.
One thing I've noticed out of watching the FFT for a while is we need
software that "finds interesting signals".
I plan on reworking the spectrum display so that there are a few
markers available that can be positioned to show signals of interest,
select this one to demod, etc. Annotations into a data base might be
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