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PCsat Critical



PCsat critical.
The good news is that at about 0152z on 16 Nov we did get connected and
did get both UHF receivers  off and both redundant transmitters isolated,
and the DIGI turned off for maximum conservation of critical power.
Battery volts were down to 1.0 volts per cell but picked up a bit.

The bad news is that when we disconnected the command channel, an
individual decided to try his hand at it.  The ensuing 10 retries of the
PCsat command channel to this individual at 4 lines a piece (40 lines) ran
the batteries down to a damaging .84 volts per cell and will probably
cause a reset and loss of all settings during the remainder of the
eclipse..

Users must understand that the health of PCsat depends on all of us.  It
is a simple design and does not have all the protections that a good
satellite design should have.  Its mission is as a UI digipeater.  There
is no reason for any user at any time to ever attempt a CONNECTION either
VIA PCsat or TO any of the callsigns on PCsat.  It is for UI packets only.
CONNECTIONS are a tremendous waste of very limited  power.  Help us to get
this word out to HAM's worldwide...

PCsat runs on a simple set of 12 AA nicads like in your HT.  But when it
goes to SAFE mode for maximum probablility of command, it turns on dual
redundant receivers and dual redundant transmitters.  The backup receivers
consume more than twice the receiver load and the transmitters in this
mode draw a whopping 12 Watts for every packet.  When this happens there
are 3 things that need to happen soon:

1) The command station must connect and turn off unnecessary receivers (if
the primaries are working) and Isolate the transmitters if they are
working.

2) Users should eliminate any additional load on the transmitters, by
ceasing all UI transmissions VIA PCsat or any of its callsigns.

3) Users must NEVER attempt any "CONNECTIONS" either TO or VIA PCsat at
any time, safe-mode or not, ever.  Retries and ACKS are killers and can
quintuple the load on PCsat far over its power budget.  THis forces SAFE
mode and we are back to square one again...

We have been trying to teach users that typical CONNECTIONS are *bad* for
the last  10 years of MIR, SHuttle and ISS operations.  But they had LOTS
of power.  PCsat doesn't and cannot survive the resultant loads.

I am sharing this with everyone, because PCsat is a simple satellite, easy
to understand since it is no different from your TNC in your shack.  The
only difference is that we can never ever get back to "fix" it if
anything goes wrong.  So help us by operating via PCsat only in accordance
with recommended operating procedures and it should last...

Thanks!
de WB4APR, Bob

On Thu, 15 Nov 2001, Bob Bruninga wrote:

> Sorry PCsat users,
> On the next opportunity I am going to have to turn digi OFF.  Seems like
> on every pass over the northern hemisphere in the  prime-time evening
> hours while in eclipse, PCsat is running outta juice  before it gets back
> to sunlight..
>
> I want to max conserve batteries until Saturday nights LED test.  So
> please, no operations for the next 2 days (or more) and in any case, lets
> get the word out that if you ever see 11111111 in the telemetry and
> unless otherwise told, do NOT use PCsat.
>
> de WB4APR@amsat.org, Bob
>
> PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
>
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> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

de WB4APR@amsat.org, Bob

PCsat WEB  page     http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ:       http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs     http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages     http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES     http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite  http://www.toad.net/~wclement/bruninga/mic-lite.html

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