Tuner frequency incorrect with rtl_fm command + stream bandwidth used

Need help installing or figuring out something about your SDR? Ask here.
Post Reply
Posts: 4
Joined: Sun Jan 21, 2018 5:12 pm

Tuner frequency incorrect with rtl_fm command + stream bandwidth used

Post by keukenrol » Sun Feb 17, 2019 5:55 pm


I have a raspberry pi setup with two dongles (1 for ADS-B and 1 for regular SDR use).
Until today, when I wanted to listen to a certain frequency (FM or AM mainly) I used the command line over SSH to start the device using the rtl_tcp command.

Instead of needing a device to decode the stream, I would rather like the pi to send audio over the network and only use the command line to change parameters.
I followed this guide to do that: https://medium.com/@luigifcruz/listenin ... 49c5abe878

I noticed that when using the rtl_fm command it does not tune the device as well as the rtl_tcp command. There is a serious frequency deviation (more than commanded), while the tcp command is spot on.
What is going wrong?

Secondly, I would like to stream the audio using minimal bandwidth, I currently have this command:
rtl_fm -g 44.5 -f 120775000 -M am -s 250000 -E deemp -d 1| sox -traw -r8330 -es -b16 -c1 -V1 - -t flac - | cvlc - --sout "#standard{access=http,mux=ogg,dst=}"

However it is far from efficient. I have been looking for the commands of sox and cvlc but I cannot seem to get the hang of it.
Best would be to get voice codecs as the output would be voice, I dont need the high bitrate of flac.

Best regards
SDRproblem.PNG (21.13 KiB) Viewed 1331 times

Post Reply