[Discuss-gnuradio] Measure FM frequency deviation

[Tom Theisen]

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