ARRL

ARRL Satellite Bulletin ARLS002 (2008)

SB SPACE @ ARL $ARLS002
ARLS002 AO-16 Satellite Serves as Voice Repeater

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Space Bulletin 002  ARLS002
From ARRL Headquarters  
Newington, CT  January 23, 2008
To all radio amateurs

SB SPACE ARL ARLS002
ARLS002 AO-16 Satellite Serves as Voice Repeater

Launched in January 1990, AMSAT-OSCAR 16 (AO-16) -- a digital
satellite -- has been unavailable for use while the command team
dealt with a serious computer problem.  The satellite has since been
recovered, and is now a voice repeater, at least for an unspecified
"test period" using FM voice on the uplink, but SSB voice on the
downlink.

Since AO-16 was recovered approximately six months ago, the command
team -- Bruce Rahn, WB9ANQ, Jim White, WD0E, and Mark Hammond, N8MH
-- attempted to reload the satellite software almost a dozen times
without success.  The team performed a series of memory tests that
pointed toward a hardware failure that prevented the spacecraft
software from restarting successfully.

AMSAT Vice President of Operations Drew Glasbrenner, KO4MA, said,
"After concluding that the spacecraft computer system was damaged,
and as discussions about decommissioning were taking place, Jim
recalled a series of low-level commands that Tom Clark, K3IO,
included in the spacecraft design during construction.  One of these
commands allows an uplink receiver to be directly tied to a downlink
transmitter.  The twist is that the uplink is regular FM, but the
downlink via the BPSK transmitter is DSB (Double Sideband).  Mark
placed the satellite in this mode early this week and did some
testing."

Glasbrenner also said the satellite hears very well; the reduced
bandwidth by using either USB or LSB on the ground station receiver
"allows for a very robust downlink.  Tuning the downlink is just
like on a linear transponder, meaning it is tight and with fast
Doppler.  Uplink tuning is not required, just as with the FM mode
V/U satellites.  My personal observations include being able to
access and hear the satellite within one degree of the horizon, much
lower than any other current bird for my location [in Florida]. This
should be an easy satellite with omni antennas and a 70 cm preamp."

Glasbrenner said that he would like to open the satellite to general
use for a test period.  The uplink is 145.920 MHz FM, and the
downlink is 437.026 MHz SSB +/- Doppler shift.  He asks that users
restrict their uplink power to a reasonable power level, and do not
transmit without being able to hear the downlink; all general
single-channel guidelines apply.  Please submit reports via e-mail
at, ao16@amsat.org.  "Enjoy this bird's new life!" Glasbrenner
said.
NNNN
/EX