Some (current) APRS Amateur Satellite history:
CONSTRUCTION: For what it is worth, After 20 years, both PCSAT side A and B transponders (digipeaters) remain semi-operational as the longest running student project satellites in space.. Further they were built desk-top style using simple off-the-shelf Kantronics KPC-9612 TNC's and Hamtroncs kit TX/RX boards. All parts are.COTS and chips are in sockets. Batteries are AA NiCd's. There are no CPU's on board. All command/control/telemetry is just what is inherent in the TNC's. Only thing we did was replace all electrolytic caps with tantilums. Having no clean room, we just used kem wipes and alcohol to wipe off all the fingerprints and dust before bagging for delivery.
NOTE: No one should be so cavalier if their mission is REAL and costing great amounts of expectations and money. Back then it was just a free ride with no expectations other than student involvement.
SAFE MODE (NOT): The only thing wrong was stupid thinking on the power budget. As our first satellite, we put on dual A/B systems AND additional 9600 baud DUAL UHF backup link receivers so that we had QUAD backup command RX capabilities in case of failures. The problem was we decided that all systems must come up on power-up in order to have access to all the redundant backup reset and command capabilities if needed and (DUH!), if all was OK, we would turn off the unnecessary backup-UHF receivers and un-crossconnect the transmitters.
TOO-COMPLEX LOGGON: That is what kills it (on every orbit). If the reason it reset is because of low battery, then the last thing you want is for EVERYTHING to be ON when you are coming into the sun and trying to charge back up. There is not yet enough power to get the command in to command off the unnecewssary systems! Further, the commands required a full two-way AX.25 connection requiring 5 packets to exchange the password challenge and password response. All of which fully loaded the cross-connected XMTRs while trying to recover. power.
NO CPU or OPERATING SYSTEM: PCSAT had no programmable CPU. Just two-dual-port TNCs and 2 VHF XMTrs and 2 VHF RCVRS, and 2 UHF 9600 baud RCVRS. There was nothing in which to put SMART-safe-mode power-up thinkinng. Hence the fatal flaw to just power up everything and command later... duh...
WITH LUCK: But luckily, the orbit occasionally has short eclipses and longer sun side (about 1 hour) which gives it enough time to sometimes have enough power to do a few user digipeats. Though after only a few, that usually kills the battery for the rest of the orbit.. We long since gave up trying to go through the entire secret logon process to try to turn off the extra UHF receivers, only to have it last another' 10 minutes or so until the next eclipse. and so that is why it just does its thing and sometimes people are successful, or not.
MISSION: Side A of PCSAT (AKA W3ADO-1) remains operational on 145.825 digipeating when power permits. Same for side B which has a digipeater with a 144.39 MHz downlink for use over North America which at the time was thought would be useful for communicating *TO* normal 144.39 travelers who may be traveling outside of range of the terrestrial network for a while.
TODAY, one of our sysops tested the side "B" and confirmed it remains operational. That is why you might occasionally see PCSAT-11 in the APRS logs. Although within the rules at the time of launch, in the last decade, the IARU has officially made notice that operation of satellite downlinks in the old 144.30-144.40 are no longer authorized. Besides, we never came up with a good use of the side B anyway. (Broqdcast an APRS message to all North American mobiles, or special traffic to a specific mobile).
Of course, we learned those lessons and had 6 successful followon APRS satellites with only the last two (PSAT and PSAT2) had programmable CPUs. (Basic Stamps). See http://aprs.org/sats.html
On Thu, Jul 8, 2021 at 9:54 AM McKinley Henson <ke4azz> (PcsaT sysop) wrote:
I was able to digi off PCSAT-11 this morning, but no Igates picked it up… I have to turn my Igate off, otherwise it makes the network dump the packet picked up by others… tried filtering but it still dumps.
Fm KE4AZZ To APRS Via PCSAT-11* <UI pid=F0 Len=36 >[08:44:42] =2702.06N/08209.93W` KE4AZZ EL87
Fm KE4AZZ To APRS Via PCSAT-11* <UI pid=F0 Len=36 >[08:44:47] =2702.06N/08209.93W` KE4AZZ EL87
Fm KE4AZZ To APRS Via PCSAT-11* <UI pid=F0 Len=36 >[08:44:52]
73 McKinley Henson KE4AZZ