Re: [Discuss-gnuradio] Hi

[Eric Blossom]

On Fri, Feb 01, 2002 at 01:48:35PM -0000, Philip Mackenzie wrote:
> Thanks for that info.
> 
> I've tried your code with my hardware, it worked really well. I changed the
> tuning parameters, etc in the microtune_fm_demo example and its running at
> ~30% CPU time on a P4 2GHz. Sounds good too!

Glad to hear that it's working for you.

> Unfortunately I think you're correct about windows virtual memory control,
> although I'm trying to see if theres an easy way to get around this. I'm
> using the computer boards driver at the moment and its sort of restrictive.
> E.g. you have to call a special function to 'copy' the data from kernel to
> user space. Not good at all for swradio.

<free-software-plug>
Part of why we like software where we have all the source is that we
don't have to put up with other people's design decisions.
</free-software-plug>

> That Microtune unit sounds interesting.  My IF amplifier is limiting our B/W
> to only 300KHz at the moment. This allows us to use bandpass sampling at
> 2MHz to obtain a nice signal, but its still quite restrictive. I think I'll
> try to get a microtune unit instead. Are you able to fill the full 12 bit
> range (1 or 5 volts) from the output of your tuner?

Yes.

> Have you been able to
> use an antenna on the unit to get live signals or are you feeding it a test
> signal?

We're using live signals.  No preamp.  We're currently using either a
cheap FM dipole or a set of TV rabbit ears with UHF loop.  The screen
shots on the web page were all taken with that set up.
http://www.gnu.org/software/gnuradio/screenshots

Now that we understand more about tweaking the tuner AGC, we've
actually got better SNR than indicated in the screen shots.

Eric