Howto: Listen to FM broadcasts on Dreamcatcher

  1. Install software (it’s only necessary to install once, but re-installing will not damage the unit):

sudo apt update

sudo apt install rtl-sdr sox

  1. Enable sound output through the 3.5mm TRRS connector:

        

alsamixer

        

Enable every column except the second and third by pressing “m” (for mute/unmute) when the column is selected. Use the keyboard left-arrow and right-arrow keys to move among the columns. For the second column, use up-arrow and down-arrow keys to adjust output volume. Be careful to not set it too high; if the column color changes to white, it has been set too high. Leave the third column muted.

You may have to reset theseAon every boot. Alternatively, you can save and restore them using:

sudo /usr/sbin/alsactl store

sudo /usr/sbin/alsactl restore

  1. Connect a TRRS (tip-ring-ring-sleeve) headset cable - the kind you might use with an Android phone - to the 3.5mm connector on Dreamcatcher that is labelled “headphn”. This has 4 conductors - a “normal” set of headphones has 3.

  1. Run this:

rtl_fm -f 104M -M fm -s 340k -A fast -r 32k -l 0 -E deemp | play -r 32k -t raw -e s -b 16 -c 1 -V1 -

  1. More information about the various command line options is at the rtl_fm homepage at http://kmkeen.com/rtl-demod-guide/

  1. Obviously, the most important one is the -f option for selecting the tuned frequency. You may also have to play around with the -s if the output is noisy.

  1. FM broadcasts tend to be quite powerful signals, and I have not needed an antenna for receiving any of the local stations, but in case of bad reception, just adding a sub-1M SMA cable at the LNA_BYPASS RF input of the Dreamcatcher should improve reception dramatically.