[amsat-bb] PSAT Igates needed
bruninga at usna.edu
Thu Jun 18 16:14:28 UTC 2015
We need PSAT IGates in Hawaii, India, China and anywhere in the Southern
We did a look at the IGates that are successfully injecting PSAT packets
and did a map of them on the PSAT page:
Notice that this map of stations are not all of the IGATES on 145.825 which
includes the ISS, but this is because the ISS is 14 dB stronger than PSAT.
So a station with an omni terrestrial antenna that picks up the ISS just
fine may not hear PSAT at all.
So if you have ever thought about being a satellite IGate, now is the
time. And the ideal OMNI antenna for PSAT is a simple 19.5” vertical whip
over a large metal ground plane. An even better one (+2 dB) is a ¾ wave
vertical whip (58”) over a large metal ground plane. And it is OK to keep
this antenna lower to the ground since it will not hear anything below 25
degrees anyway and in fact, the lower it is, with surroundings blocking it,
the less interference it will have.
IGATES that hear weak signal PSAT show on http://pcsat.aprs.org
All 145.825 IGATES show on the http://ariss.net page but they may not hear
Another reason to keep your Space IGATE antenna low is because they create
DONUT Hole Data NULLS. Anyone who transmits a packet on the UPLINK TO one
of these sateliltes and is heard by an IGATE direct, will be ignored on the
downlink, since the packet has already been heard. Therefere the digipeat
will not be recorded by the above FINDU.COM pages…
*From:* Robert Bruninga [mailto:bruninga at usna.edu]
*Sent:* Thursday, June 18, 2015 7:34 AM
*To:* amsat-bb at amsat.org
*Cc:* bruninga at usna.edu
*Subject:* PSAT digipeating and Position Knowledge
PSAT continues to work well, both APRS and PSK31. The downlink capture on
the PCSAT.APRS.ORG page captures most PSAT packets, but does not capture
any digipeated users if they use the ARISS path. Although PSAT supports
the VIA ARISS alias so that users can use both ISS and PSAT without
changing parameters the FINDU page does not recognize it.
At this point it is unclear what paths that FINDU recognizes.
These paths are supposed to be digipeated by PSAT:
Here is what we know:
ARISS is not recognized by FINDU.
We are not sure if FINDU recognizes APRSAT
We are not sure if PSAT recognizes PSAT
We have seen VIA WIDEn-N work on FINDU
We have been busy with deadlines on our next satellite, but yesterday we
figured a workaround on the PSAT ORBIT and MA clock. This morning we sent
the commands and will be watching to see if they work. If they did, then
PSAT will be able to know where it is, and then we can activate its APRS
POSITION packets plus individual beacons over individual continents.
Although the S#OOOMM… telemetry was supposed to be ORBIT number and MINUTE
of that orbit, the clock is totally off. SO instead of going from 0 to 95
minutes per orbit, the actual count is more like 0-61 minutes per orbit.
So, if this works, then MM is not real minutes, but is a number between 00
to 61 on every orbit. And 0 should be when the satellite crosses the
equator (actually 5 South latitude) on every orbit northbound.
Once we get that under control, then PSAT will know where it is, and it
will be able to report its own position. And we can activate its attitude
control, and we can activate different bulletins over each continent.
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