Gpredict format which sends doppler correction to a listening port in GNU Radio


I would like to ask in which format does Gpredict use to communicate with gnu radio.
I’m using predict_doppler block in gnuradio as a receiver ( I have the following configuration in Gpredict:

Radio type RX only
Rest is empty

I would like to manually control frequency via rigctld/rigctld. I tried following commands but it doesn’t work properly.

rigctld -m 2 -t 4532 -T -s 9600 -vvvvv

I would like to point out, that Gpredict works perfectly and correction is really awesome and accurate. Is it possible to simulate a similar output as Gpredict does?

Thank you for any response and suggestions about this topic.


I’m not sure if this helps, but you don’t need rigctld to use Gpredict with GQRX… Have you tried simply not initiating rigctld?


Thank you Roy for Consulting.

I would like to send packets to GNU radio manually in terminal as it would send Gpredict. I found in Gpredict manual quite a bit ifnormation about rigctl and rotctl, so I assume it uses those 2 commands.



It’s a bit confusing… rigctld is the server and rigctl (without the d) is the client. So, if I understand you correctly, you have to use rigctl (not rigctld) to send commands to a GNU Radio program. rigctld is the server that e.g. gpredict sends comands to. However, a GNU Radio program using gr-gpredict-doppler implements this server functionality.


Hello Alex,

I’m aware of the server and the client differences in those commands. I tried both, but I wasn’t successful with the connection to the doppler block in GNU radio which is waiting for the right input signal.Usually, I got this response:

[doppler] Waiting for connection on:
[doppler] Connected from:
[doppler] received unknown command: \dump_state
[doppler] Disconnected from:

I’m not quite sure what Gpredict does when I hit the Engage button in the Radio Control tab. I assumed it opens a server, and then sends updated information about doppler frequency to the block in GNU radio.


I don’t remember the exact sequence, but I would guess that when you hit Engange in gpredict, it will connect to the server and send set/get frequency commands, nothing else.