SAL-E 5-04-2026
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Got strong signals for the first time today, uploaded 20 packets between 13:55 and 13:59 UTC and of course filled out the form for a QSL card.
I’ve noticed that the PID of the AX.25 packets is always 0xcc (ARPA Internet Protocol).
Since the decoder (cp16.ksy) discards the 29 bytes of IPv4 and UDP information, is the implementation of a layer 3 protocol by any purpose?
Daniel
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Hi Daniel,
Yes, as you noticed, we use the IP stack. All of our packets, both for uplink and downlink, use IPv4 and UDP. For downlink, this information is used for our ground segment to determine where to send responses (based on the ip and port). Our communication processes (both onboard and on the ground) are built around the IP stack, so we use the same for the beacons for commonality.
In the case of beacons, we know it is a beacon if the destination IP is 224.0.0.1 and we also verify that satellite (source IP) is correct (the same as the satellite our ground station is tracking). I discarded the bytes since there is no need to actually store them, but I could modify the decoder to also verify those two IPs. Let me know if that would be beneficial.
Alex
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