Hi,
after i got rtl_fm run on Raspi 2 with Debian Jessie .. now i have some additional noise in the FM demodulated audio!
With a "raw" recording (see attachment) i can see an additional carrier at the DC frequency of the demodulated output. That corresponds to the tuned frequency (= 433.25 MHz) parametrized to rtl_fm. Due to calibration error, the FM carrier has some offset: ~ -1.3 kHz as visible in screenshot. The DC carrier does demodulate to some distortion!
Option "-E dc" does not help, cause that removes a DC in the demodulated output. An additional option to filter DC before demodulation does help a bit .. but does not solve the problem, which looks to be introduced earlier ..
I would not have expected such a DC, cause IMHO it's produced whilst downconversion or filtering. It's not the RTL dongle's DC, which should be far far away by 1/4 of the high samplerate.
Someone else seen this problem? Does anyone have a useful solution?
kind regards, Hayati
