Re: [Discuss-gnuradio] NBFM

[James Cooley]

I'm having a bit of trouble getting this one to work...

I'm running the input through a microtune 4937 frontend, so that the IF 
is 5.75e6. I've changed Matt's nbfm script just to adjust this IF_freq.

Is there anything else that needs to be done? I'm trying to tune to a 
known station, the weather, 162.475.

-jamie




Chuck Swiger wrote:

> At 11:54 AM 2/17/2005 -0800, you wrote:
>
>
> > I realized about an hour before a demo last night that we didn't have 
> > narrowband
> > FM (like ham and public safety), so I coded it up.  Its in the
> > gnuradio-examples package, and it is commented rather liberally.
> >
> > It will require an update on the gr-wxgui stuff too.
>
>
> Love it - picked up the local noaa weather (162.4 here) wx right off.
>
> I get some kind of strong 1Kz 'noise peak' that's pretty annoying, almost
> a constant whistle - have no idea where it's coming from (maybe my
> hardware) - it's on local police too.
>
> Anyway, quick software mod: add a notch (comb) filter!
>
>         # notch filter, 1Khz at 16K sample rate
>         taps = [1]              # original signal, no delay
>         for i in range(1,8):    # .5mSec ( 1/2 cycle at 1Khz ) = 8/16000
>             taps = taps + [0]
>         taps = taps + [1]       # signal delayed .5mSec cancels self 
> at 1Khz
>         notch = gr.fir_filter_fff (1, taps)
>
> then wire it in - end of problem.
>
> --Chuck
>
>
>
>
>
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