[amsat-bb] ISS Beacons (APRS-FAQ!)
bruninga at usna.edu
Tue Apr 19 14:55:00 UTC 2016
Re ISS beacons: Here is the beacon gouge for APRS via ISS
APRS was designed for channel sharing using the ALOHA protocol. That is,
peak success occurs at around 20% channel capacity. For 1 second packets,
that's only 12 packets per minute per digipeater area. This usually means
maybe 5 mobiles at a 1 minute rate and 30 other home stations and weather
stations, etc at a 10 minute rate using 1 hop and 60 other assets
beaconing every 30 minutes when using the maximum of 2 hops.
But on ISS, the digi neighborhood covers the entire USA at once!
So, it is a travesty that people transmit unattended beacons via the ISS
at such high rates causing nothing but interference with those trying to
actually operate the pass.
See the original APRS-ISS FAQ: http://aprs.org/iss-faq.html
It recommends 1 beacon per minute for LIVE keyboarders,
1 beacon per 2 minutes for active special live mobiles engaged in travel
or special operations,
and one beacon per 5 minutes for unattended status/position reporting.
The goal is to optimize the channel for live operators during a pass but
for non-moving remote unattended position/status packets to be successful
only about once a day (NOT every pass!) on http://ariss.net
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