Configuring Gpredict/interfacing with GQRX using Python Script

Gpredict
1

Hi all,

I’m writing a script to automate the recording process for my ground station. I want to accomplish the following functions from my script and I am not sure how to do it:

  1. Press the engage button in the GUI to engage GQRX and my SDR
  2. Press the track button to allow the signal to be adjusted for doppler shift
  3. Toggle the record option in GQRX.

Any and all information appreciated, even if it is just a pointer on where to look next. I’m so close to getting my ground station up and running I can taste it. Just need to vault these last few hurdles.

Thanks for your time,

Lorcan.

2

Hi Lorcan,

Just the other day, somebody posted on the gqrx list some trick to send keyboard messages:
https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/gqrx/dWHsvQyP4cM/vJJsax2UAAAJ

Perhaps you can use that.

Also note that gpredict has the “autotrack” option as well as AOS/LOS signaling, which gqrx can use to start/stop audio recording.

3

Thanks for getting back to me.

How do I enable autotrack and AOS/LOS signaling?

Thanks for your time,

L

4

Autotrack is enabled in the module menu, AOS/LOS signalling in the radio configuration dialog.

5

Hi Alex,

I’m trying to decode telemetry data from the STRaND-1 cubesat. The satellite I’m targeting is using a 9600bps ax.25 FSK modulated packet radio. Which demodulator do I use in GQRX? Is it the CW-L demod?

Thanks.

Lorcan.

EDIT: I can’t find the transponder in the drop down menu of the Gpredict radio control panel.

6

It depends on what the data decoder requires as input. I think normally they require the audio to be FM demodulated already, so you need to use narrow FM mode and select deviation 5 kHz or maybe more. Make sure the filter is wide enough (20+ kHz ?).

Otherwise USB can be considered as the “raw” demodulator.

7

Thanks for getting back to me. I’m assuming I will leave everything default until a bit of trial and error can determine if it works? I was under the impression that for such a weak signal I should turn the gain right up on the RTL but perhaps I am mistaken?

8

Adjust the gain for maximum signal to noise ratio, but avoid front-end overload, which normally manifests itself as reduced signal to noise ratio :wink:

1 Like
9

How do I adjust for maximum SNR? I tried setting to hardware controlled gain. Still not managing to pick up anything.

10

One more question for you. Which settings would I use for Meteor M2 signal recording? Specifically, which mode do I use?

11

There is no mode for LRPT in gqrx. So you can only record IQ and process that with some external software. I can’t help with that, sorry.

12

Thanks for getting back to me. Just to confirm, the IQ is the baseband right?

13

I suppose you can call it baseband, though what baseband is depends on the context. For instance, in voice communication the audio would be the baseband :wink:

Anyway, I am referring to the IQ recorder, which will record the samples coming from the device without any processing.

14

Understood. Thank you for your help!