[Discuss-gnuradio] Measure FM frequency deviation

Hello everyone,

I'd like to measure FM frequency deviation and modulation index of an FM
radio broadcast radio station. Unfortunately I can't use the bessel null
method as I can't influence the modulation of the transmitter.

I've tried a patched version of rtl_fm [0] with an rtl-sdr dongle to
maybe find out how it's done there to implement it in GNURadio.
Unfortunately, while working well with narrowband FM it seems to have a
very large error when used with wideband FM signals. (I don't know if
it's even meant to be used with wide band signals..).

Could you please give me some hints on how I could implement this in
GNURadio? Modulation index would be nice to have, but I'm really after
the freq. dev.

Many thanks & best regards,
Tom Theisen


[0] http://comments.gmane.org/gmane.comp.mobile.osmocom.sdr/814

Hardware I have: USRP N210, hackRF compatible CCCamp15 badge & various
RTL-SDR dongles


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