NAL SHOUT ts, User Manual, Page: 58 / 62

SHOUT ts User Guide Version B
Document Number: 451-92854-001B 58 of 62
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PPENDIX
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OWER
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ONSUMPTION
The SHOUT ts has an internal 1.95 A-Hr Li-ion rechargeable battery. When both the Iridium
and GPS antennas have a clear view of the sky and the battery is fully charged, the SHOUT
ts is capable of sending more than 1,500 tracking reports with the following settings: (1)
report rate of less than two hours, and (2) mailbox check rate and the report rate are the
same. Blocked or partially blocked antennas force the SHOUT ts to retry multiple SBD
transmissions for each report and, as a result, can significantly reduce the overall number of
reporting cycles.
The SHOUT ts saves valid ephemeris data after each 3D fix. The data is used to reduce
acquisition time in the next reporting cycle from cold-start to hot-start. If the ephemeris
data is older than two hours (time between reports is set for more than two hours), the GPS
receiver goes through cold-start each time it wakes up to send a report. As a result, the
SHOUT ts configured for report rate of more than two hours can only send ~750 tracking
reports.
Important: Data presented here are only estimates and are highly dependent on the
operating environment and antenna type. Data are based on measurements made with
multiple ts devices placed on the roof of NAL Research’s facility with no blockage.
Each time the SHOUT ts wakes up to send a report, it has two minutes to acquire a GPS fix
and send an SBD message. Assuming the ephemeris data is valid (less than two hours old
or time-between-reports is less than two hours), the GPS receiver takes about 5 seconds for
a position fix drawing approximately 55 mA. The Iridium transceiver takes about 15 seconds
to transmit an SBD message drawing an average current of 190 mA. The SHOUT ts circuit
draws about 60 mA during a 20-second reporting cycle. The entire reporting cycle consumes
~1.12 mA-Hr of battery power. If the Iridium antenna is blocked or an overhead Iridium
satellite is not available, the Iridium can potentially stay on for another 100 seconds in
attempting to send a report. This results in additional consumption of 9.7 mA-Hr or 11 mA-
Hr total. A missed report consumes ~8.5 times more power than a ‘normal’ transmitted
report.