Gqrx and APT

[Martin Cooper]

I am running Gqrx 2.11.5 on Xubuntu 18.04 with an RTL-SDR v3 dongle. With the basics working well, I now want to try receiving from the NOAA APT satellites. The Gqrx homepage includes the bullet point:

* Special FM mode for NOAA APT

I have looked all over the place, but have been unable to find it. I've also seen a note in this forum that says "be sure to use the "APT" deviation", but have been unable to find anything like that either.

What am I missing? Where should I be looking for APT settings?

Thanks!

Martin.

[Simon Kennedy]

Hi Martin,

The settings I used to use are to set mode=NFM, filter width=45kHz, mode option Max Dev=APT 25kHz.

If you make a wav recording then to decode it (in wxtoimg at least) you need to resample the audio using sox, e.g. 

'sox inputfile resampledfile 11025'

Then to process in wxtoimg in cmd line mode: 

'wxtoimg -N -f 11025 resampledfile outputpicturefile'

Hope that helps 

Regards

Simon.

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[Martin Cooper]

Hi Simon,

Thanks very much. I've set those options and will see what happens when the next sat comes by in a few hours. I hadn't seen the APT options because I was setting the mode to WFM, per something I'd read elsewhere.

If the signal looks good as it's coming in, I'll feed it to wxtoimg via sox and see what happens.

Thanks,

Martin.

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