Hi All
I am thinking of sending a few AX25 test packets up to some satellites,
Currently I run APRS and similar so I am familiar with the workings.
Believe it or not I dragged out an old AEA PK88 from out of the cobwebs and it still works , This was running on UI-View .
My question is what are you guys running to send AX25 packets up to the sats ? I would be interested to hear about hardware and software, Whatever it is, it cant be as old as the PK88 !
My preferred modem is Direwolf. When I started with satellites, I also tried for a short time a TNC2multi, DLC7 and SCS Tracker.
As client software I started with Paxon and WPP and now I’m using Paracon, UISS and PyttiAPRS.
Thanks for the info,
Yes, Direwolf worked well on an Igate I used to run.
I assume the information for the uplink has to be assembled correctly or does the info get sent up as a beacon text, where can I obtain more info on how the uplink data should be formatted ?
Thanks.
To generate a valid AX.25 frame, please refer to the AX.25 protocol specification.
For example, to send an APRS (UI) packet via LASARsat (OK0LSR) holding my Mic-E-encoded position, I use the following command.
c000 at the start and c0 at the end is the KISS framing, necessary for the modem you are talking in KISS to (for example Direwolf).03 (yellow) says send it as an UI frame beacon.
Direwolf also allows messing with the protocol, return messages like this, but sends them out anyway.
Station address, in position 0, is empty! This is not a valid AX.25 frame.
Destination Address “” is empty.
*** The origin and journey of this packet should receive some scrutiny. ***
Hi, I’ve been wanting to experiment with satellite packet stuff, and I’ve just tried to make my own mic-e frame following the APRS/AX.25 spec. However, I noticed at the end of your frame you have the three bytes 79 2f 22. I can’t find what their purpose could be. The speed/course section seems to be optionally followed by either some telmetry or a status message, but these bytes don’t seem to be one of those.
Hi Leo,
According to
the three bytes (79 2f 22) at the end are the symbol code, symbol table ID and the Mic-E status text.
y/ (79 2f) means Yagi @ QTH.
However, I don’t remember why I chose 0x22 for the Mic-E status text.
There is no meaning. Perhaps it was just decoded correctly by Direwolf.
Thank you for the response.
I don’t know how I missed the symbol bytes. I’ve added them to my mic-e frame now.
Also, about LASARsat: I was able to see get pretty strong packets on its frequency during a pass yesterday. I’m assuming those are telemetry packets that aren’t ax.25, as direwolf doesn’t decode them. But how exactly does the digipeating work? The uplink frequency isn’t stated anywhere, so i’m assuming it’s on the same frequency as the downlink, and the satellite retransmits the received packets between the telemetry packets. Is that correct?
You are right. LASARsat sends also non AX.25 packets between regular AX.25 encoded telemetry packets.
Yes, it’s half duplex. So up- and downlink are on the same frequency as the telemetry is (436.925) and LASARsat will retransmit right after it hears you.
Just put OK0LSR into the digipeater (via) path.
Be aware that, compared to the ISS, LASARsat is not so easy to work. You’ll need much more power.
Please also check the Digipeater Dashboard.
I think power should be fine, I’m using an Arrow II antenna with an FT897D, so I can do up to 25 Watts on 70cm. I will try to contact it in a pass later today. If it doesn’t work, I’ll try another satellite. Thank you very much for the information! 
