# PSK demodulation of a sub-carrier sent over FM **URL:** \ **Category:** GNU Radio\ **Created:** [October 22, 2014, 5:32pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690 "2014-10-22T17:32:01Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [October 22, 2014, 5:32pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690/1 "2014-10-22T17:32:01Z")
Hello, I had experimented with simple PSK reception with GNU-Radio when the carrier is directly phase modulated. However I would like to know how can I demodulate a PSK transmission which is carried over a typical FM signal. Kind regards, Raydel ---
**Author:** ![Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aeb1de/32.png) [@Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/u/Raydel_Abreu_SCM2ES)\ **Post date:** [October 22, 2014, 11:32pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690/2 "2014-10-22T23:32:05Z")
Raydel Abreu (CM2ESP) wrote > However I would like to know how can I demodulate a PSK transmission which > is carried over a typical FM signal. IIRC you would just do the WBFM demod, then the PSK demod. See the gr-rds: > **[GitHub - bastibl/gr-rds: FM RDS/TMC Transceiver](https://github.com/bastibl/gr-rds)** > > FM RDS/TMC Transceiver Lou – View this message in context: [http://gnuradio.4.n7.nabble.com/PSK-demodulation-of-a-sub-carrier-sent-over-FM-tp50986p50991.html](http://gnuradio.4.n7.nabble.com/PSK-demodulation-of-a-sub-carrier-sent-over-FM-tp50986p50991.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aeb1de/32.png) [@Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/u/Raydel_Abreu_SCM2ES)\ **Post date:** [October 23, 2014, 2:34pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690/3 "2014-10-23T14:34:05Z")
On 10/22/2014 11:27 PM, madengr wrote: > Raydel Abreu (CM2ESP) wrote > > > However I would like to know how can I demodulate a PSK > > transmission which is carried over a typical FM signal. > > IIRC you would just do the WBFM demod, then the PSK demod. See the > gr-rds: [GitHub - bastibl/gr-rds: FM RDS/TMC Transceiver · GitHub](https://github.com/bastibl/gr-rds) That sounds correct. I know hams sometimes do this to get better transmissions when using their HF gear. M ---
**Author:** ![Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aeb1de/32.png) [@Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/u/Raydel_Abreu_SCM2ES)\ **Post date:** [October 23, 2014, 3:47pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690/4 "2014-10-23T15:47:52Z")
Thank you Lou and Martin. Will try and take a look. One more thing is there any extra to do if the PSK signal is ±67 degrees instead of nomal 90 degrees or the PSK demodulator just handles it as usual. Thanks, Raydel 2014-10-23 8:32 GMT-04:00 Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid): ---
**Author:** ![Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/aeb1de/32.png) [@Raydel\_Abreu\_SCM2ES](https://www.ruby-forum.com/u/Raydel_Abreu_SCM2ES)\ **Post date:** [October 24, 2014, 12:14pm UTC](https://www.ruby-forum.com/t/psk-demodulation-of-a-sub-carrier-sent-over-fm/232690/5 "2014-10-24T12:14:50Z")
On 10/23/2014 03:36 PM, Raydel Abreu (CM2ESP) wrote: > Thank you Lou and Martin. > > Will try and take a look. One more thing is there any extra to do if the > PSK signal is ±67 degrees instead of nomal 90 degrees or the PSK > demodulator just handles it as usual. I’ve never seen this before, but you’ll have to play around with the constellation objects. Look at the Python code for PSK for some pointers. M