PCSAT2 ACTUAL POWER REQUIREMENTS                           15 APR 2003
----------------------------------------------------------------------
                                                                WB4APR
15 July 2005 revised to better detail beacon mode dutycyles
15 Nov  2005 updated due to TLM only on one side at a time

The measured currents for the PCSAT2 Comms system full-up Prototype:

120 mA (12 to 16 v)  RX Critical power (EVA plug in place)
190 mA (12 to 16 v)  TX Power after both ARM relays are enabled
                     This is the nominal ON condition minimum
                     power assuming no transmissions and all
                     user transmit loads are off.
430-580 mA (13-16v)  With TXA on  (460 @ 14v), (540 @ 15v)
450-560 mA (13-16v)  With TXB On  (490 @ 14v), (530 @ 15v)
410-660 mA (13-16v)  With TXC on  (510 @ 14v), (590 @ 15v)

These are the stock transmit currents and have not been reduced
to the exact 2 Watt limits proposed at CDR.  If we are forced to
limit our transmit powers to the exact 2W requirement, then the 14 volt
values will be used.

But all transmit powers are low dutycycle.  The nominal duty cycles are as
follows and the resulting AVERAGE transmit currents at 14 volts are shown:

PC2 1200 baud TLM 1 min A or B only     2% orbit average =  10 mA
PC2 1200 bd tlm 10 sec one side only   10% orbit average =  50 mA
FTSCE Beacon 11 sec evy 200 sec 1 side  6% orbit average =  30 mA
Digital Packet Users only (worst case)  4% orbit average =  20 mA
Crew Repeater (if used)                10% orbit average =  50 mA
PSK-31 Transponder (if used)           10% orbit average =  50 mA

Worst Case Voice Repeater always on:   50% orbit average = 250 mA

Add to this the 190 mA constant load of the receivers and TNC.  This
190 mA is independent of battery voltage.  The FTSCE DC current is about
125 mA in addition.  The PCSAT2 Transmitter currents are somewhat reduced 
at lower battery voltages the full 16 volt value will be assumed here.   
This yields the following whole orbit averages for the conditions shown:

125 mA  Full time load of FTSCE system
PLUS
120 mA  Lowest power mode of PCSAT2 with ARM relays OFF
190 mA  Armed and operational but with no transmitter activity
200 mA  Basic 1 minute 1200 baud telemetry on both A or B sides
230 mA  FTSCE beacon and 1 min 1200 baud telemetry on one side
270 mA  FTSCE and one side at 10 sec rate
320 mA  FTSCE and both sides 10 sec 1200 baud telemetry and beacons
340 mA  Nominal mode And Digital Users
390 mA  Nominal mode and Digital and typical PSK31 users 
390 mA  Nominal mode and Digital and typical Repeater 
535 mA  Worst case scenario

Add 80 mA if RX heaters are turned on in any mode.

Thus, we can manage our PCSAT2 power from a minimum of 1.9 Watts (all off) 
or 3.2 Watts while on, 4.3 W nominal up to a maximum of 8 Watts  if we turn 
on everything...  But always there is the additional 2W of the FTSCE
experiment.

Bob Bruninga
USNA Satellite Lab