RTL-SDR / SoX help - White noise

[xantegh]

Community,

I heard @blantonl yesterday on The Scanner Guys YouTube channel mentioning that he is recently more focusing on SDR, so I'm hoping that any of the experts in his team or in this community, in general, can help me out with optimizing the quality of the audio files generated so I can get a clean stream later on.

here is a recording for airband where you can hear so much of white noise in the background although the communication was very clear and loud on my BC15X connected to the same Stridsberg coupler.

below is my full command line which I copied from one of the SDR blogs.

pi@rx01:~/dev $ more rec2.sh
FILENAME='recsox.wav'
rtl_fm -M am -f 123.9M -p 96 -s 16k -g 49.2 -l 200 | sox -r 16k -t raw -e signed -b 16 -c 1 -V1 - $FILENAME sinc 200-4500 silence 1 0.50 0.1% 1 2.0 0.1% : newfile : restart

Appreciated

 

[xantegh]

Oh and thank you @N9JIG and Jonathan Higgins for putting this live channel

 

[a417]

for brevity...and a first things first approach...I am only addressing the signal source part...not the audio path & subsequent processing.

rtl_fm -M am -f 123.9M -p 96 -s 16k -g 49.2 -l 200

You are dumping near absolute maximum gain in with the -g 49.2 flag. Try lowering that by half and see if the noise floor comes down. If you have good signal in other units on similar antenna sourcing, you might not need much gain at all. Remember, RTL-SDRs are cheap devices that don't handle too much signal too well...dial it back and see if it significantly improves the audio.

as for the squelch, that is controlled by the flag -l 200, which you have set at 200. Do you know why it is set at 200? Was this intentional? Start with it at 0 and go up until you get something more like your desired output.

Lets see if the issue is not completely iatrogenic and can be easily remedied.