Decoding the new AX.25 packet satellites
I have several raw IQ captures from last few days with the new satellites passing and am trying to decode the AX.25 packets from two of them. I'm using SDRSharp to reply them and pull the signals out using USB mode. I've already replayed them successfully and decoded both JY1-Sat and AO-95 using their respective software packages, but I'm having trouble figuring out ITASAT and MOVE-2. I'm using Virtual Audio Cable to loop back the audio and UZ7HO Sound modem in an attempt to decode them. For ITASAT, it's set to 1200 bps BPSK and for MOVE-2, I'm using the 9600 baud variant of BPSK Sound modem from his site. However, efforts have been fruitless to get it to resolve any packets. Any pointers for these satellites would be appreciated.
73s Loren K7IW
Hi Loren!
On the DK3WN status page ( http://www.dk3wn.info/p/?page_id=29535 ), Move-2 is listed with 12k5 BPSK modulation. I'm not familiar with a software modem for that, but would love to get setup for it if anyone knows where it can be found.
You're right that ITASAT is listed with 1k2 BPSK AX.25 modulation, so you'll need the 1k2 BPSK version of UZ7HO's "SoundModem" from:
http://uz7.ho.ua/packetradio.htm
... in the "Other-Versions.zip" file download. Don't forget to use USB demod in your playback and be sure to center the packet right in the middle of your audio output -- and in the exact same spot that you have the brackets set in the SoundModem app. For 1k2 BPSK, I normally output 3k of audio bandwidth and adjust the RF tuning to center the packets right on the 1500 mark. Of course, you have to jump back slightly in your recording while making small RF tuning adjustments so that the output audio is in the "right" place.
Here's a tweet that I posted tonight regarding the playback of PW-Sat2 which also uses 1k2 BPSK. In the first screenshot on that tweet, you can see how I'm doing that in HDSDR. (Never touch the audio output or SoundModem settings... do all your adjustments on the RF tuning to center the packet)
https://twitter.com/scott23192/status/1070522065646706688
-Scott, K4KDR
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On Wed, Dec 5, 2018 at 8:04 PM Loren M. Lang penguin359@gmail.com wrote:
I have several raw IQ captures from last few days with the new satellites passing and am trying to decode the AX.25 packets from two of them. I'm using SDRSharp to reply them and pull the signals out using USB mode. I've already replayed them successfully and decoded both JY1-Sat and AO-95 using their respective software packages, but I'm having trouble figuring out ITASAT and MOVE-2. I'm using Virtual Audio Cable to loop back the audio and UZ7HO Sound modem in an attempt to decode them. For ITASAT, it's set to 1200 bps BPSK and for MOVE-2, I'm using the 9600 baud variant of BPSK Sound modem from his site. However, efforts have been fruitless to get it to resolve any packets. Any pointers for these satellites would be appreciated.
73s Loren K7IW
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Loren M. Lang -
Scott