Re: [Discuss-gnuradio] Measure FM frequency deviation

[Tom Theisen]

Hi Anders,

On 02/25/2016 09:41 AM, Anders Hammarquist wrote:

Thanks a lot for your suggestion, sounds good! I'll try to implement that.

> If it's a steady sine wave a
> while is a cycle, if it's a broadcast FM station without RDS and other
> subcarriers, probably a few minutes to get both speech and music).

It's an FM broadcast station with RDS and stereo by the way, so quite a
few things going on in the baseband.

Would RDS (or stereo) change anything? I'm guessing not since everything
still needs to fit into that max +-75kHz deviation window.

If I understood that correctly these +-75kHz, together with 25kHz guards
on both sides form the 200 kHz channel width allocated to an FM
broadcast station.

> Once you have that, figure the bandwidth (bw) of the FM signal, and the
> maximum frequency (fmax) in the demudulated signal.


Hmm, now that I think about it, with RDS fmax would always be 57kHz no?
(RDS at these 57kHz would be the highest frequency in the baseband.)
I guess I'm mixing a few things up here :/. Could you elaborate on where
to get fmax from please?

It makes sense to me if the signal is mono without any subcarriers, but
not anymore with all that thrown into the baseband.


Many thanks,
Tom