I would like to detect the phase (only) of a standard FM transmitter carrier over the air while it is modulated, while at the same time avoiding receiver threshold effect.
Typical commercial FM transmitters use +/- 75 kHz carrier deviation and modulating frequencies of 15 kHz or higher. I need to lock to the FM carrier and track it while it is modulated, and recover just the steady-state carrier phase. I'd also like to avoid the usual 10 dB threshold effect in order to achieve maximum sensitivity under weak signal conditions.
Can I do all this using a PLL detector and an SDR? If I understand correctly, the loop bandwidth would be made narrow (say, 1 Hz), therefore removing the modulation and leaving only the carrier itself. Eliminating the limiter should eliminate the threshold effect and allow the PLL to track the carrier down into the noise for maximum sensitivity.
Any thoughts or suggestions will be appreciated.