TELEMETRY DESCRIPTION FOR PCSAT2                25 AUG 2005
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Updated 3 Dec 2005

PCSAT2 has 20 channels of telemetry becuse we used 4 pole
multiplexers on each of the available 5 analog channels built
into the KPC-9612 TNC.  So first, one has to realize that
at one frame every 10 seconds, it takes 40 seconds to get
a complete telemetry set and the only values sampled at the
same time are the 5 in each group.  The others are uncorrelated.
Also there are some subtle things to observe as well. Since we 
needed two additional data points after the system was mostly
designed, we fudged some additional data points:

FAIL-SAFE-120hour-TIMER:  There is a 120 hour binary counter
that counts up if it has not been reset by ground command.
This assures that after a possible worst-case lockup of
both TNC's and the 2 other methods of TNC reset, that a
reset of both TNC's will be forced.  We cannot read the 
timer, but the 60 hour bit is wired to short the 5volt
telemetry channel to ground.  Thus, on the 11 frame, if you
see the 5v bus showing near 0, then the timer has passed
the 60 hour point and the command station should get involved
and clear it.

POWER SHUNTS:  For man safety, we had to have a fail-safe
load on the batteries that could prevent overcharge of 3
cells if one of the 4 cells failed as a short.  But this
LOW-V-SHUNT also will run down a good battery of 4 cells
if it is not toggled off.  Again, we had no spare telemetry
channel, so if the LOW-V-SHUNT is on we had it short to
ground, the thermister on the battery.  Thus, a -30 or null
value on that channel indicates this LOW-V-SHUNT condition
which must be toggled ASAP by the command station.  These
conditions show up on the BATTERY TEMP chart.

RX HEATER CURRENTS:  If we ever turn on the RX heaters, the
current is drawn from the TNCA circuit and so you will see
the increased current there.  This current is dependent on the
temperature.  If it is hot, the heaters only draw about 50 mA
at 40C but 100 mA at -6C.  Also, the RX control circuit drops
out at 13.3v to avoid running the battery too low.

PSK-31 TRANSPONDER:  Not only will you see the high TXA
transmitter current when the PSK31 transponder is on, but also
the PSK-31 Receiver is powered by the TNCB circuit and so it 
will show about 15 mA added current when the receiver is on.
(The PSK-31 mode is currently inop).

MINOR ITEMS:  The RXA and RXB currents will show no change unless
the hardware fails.  Similarly, the TLM and RX temperatures as
well as the DECK and BATTERY temperatures will all be about the
same since they are all mounted to the same thick aluminum plate.
The cumulative battery CELL voltages are also of little interest
except to the power system manager, but the total BATTERY VOLTS
tells you the sum and says a LOT about the state of charge of the
battery.

de Wb4APR, Bob