SB SAT @ AMSAT $ANS-229.01
ECHO Update - 16 August 2004

AMSAT News Service Bulletin 229.01From AMSAT HQ
SILVER SPRING, MD.  August 16, 2004
To All RADIO AMATEURS
BID: $ANS-229.01

Why do we use PL mode on Echo?

There are several reasons to use PL mode (CTCSS Decoding) on Echo.  First,
and simply, power.  Recent data collection shows that on average, Echo's FM
repeat transponder is on for less than 40% of an orbit.  There are orbits
where that number is as high as 65%, but the average is below 40%.  We are
conserving over 60% of the power that would have been consumed by TXB by
using PL mode.  We are working on software to maximize the power available
by turning up the transponder output power level when our solar panels are
illuminated and we have charged the batteries after eclipse.  When that is
completed, we will be able to take advantage of our conserved power.

The second reason is QRM.  In PL mode we don't have to listen to the
illegal traffic on our amateur bands or any other signal not intended for
the satellite.  We still have to compete with them to capture the receiver,
but at least we don't have to hear them in our downlink.  Echo will not
pass a signal to the transmitter in PL mode if it does not have the correct
tone sent.

Another reason is by closing the audio path when no PL is present, the
unmodulated carrier is heard for the duration of the squelch tail.  This
can be used as a good measure of how well we are hearing the satellite.
Without PL filtering uplink noise is heard which is sometimes difficult to
differentiate from the case where we are not hearing the satellite at all.


Experimenters Wednesday

Thanks to all the participated in the 11 August Exp Wed PBBS test.  Close
to 50 messages were sent to the PBBS system by over 25 stations.  It was
noticed that many other stations accessed the bird that did not upload a
message.  TXA was operating at 1 watt output during the PBBS test window.

Experimenter's Wednesday will not be scheduled for this week, 18 August.


Telemetry Gathering

I would like to encourage stations to continue to gather and submit
telemetry from Echo.  During the week of 16 Aug to 20 Aug the WOD data
collection package on Echo will not be running. Therefore the only TLM data
we will have for that time will be from the users.  So, please continue to
copy the digital downlink when you can.  The TLM rate will be increased up
to 10 seconds over that week period.  It normally runs at 30 secs to keep
the WOD files a reasonable size.

[ANS thanks Mike, KE4AZN and Jim, WD0E for the above information]

/EX