ORBCOMM OG2 Modem Integration Manual
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3.2
VHF Receiver
3.2.1
Receive Modulation
The transmitter uses Symmetric Differential Phase Shift Keying at 4800 bits per seconds.
3.2.2
Minimum Detectable Signal
The modem receives ORBCOMM downlink signals with at -120 dBm or better under all operational
situations with a BER no worse than 1 x 10
-5
.
3.2.3
Acquisition Frequency Range
The modem acquires ORBCOMM downlink signals over all operational situations in the frequency
range: 137.1250 to 137.8750 MHz. This includes all effects of internal oscillator uncertainty in
addition to Doppler effects which may be as much as ±3200 Hz during times when satellite is visible
to the modem. Further, the Doppler rate of change may be as high as ±28 Hz/second.
4.
Power Supply
The power supply is designed to operate in an efficient mode at all times. The processor has power
available continuously. When the processor is in a low power mode, the quiescent current can be
as low as 3 uA. Power sections required for frequency generation, receive modes, and transmit
modes are turned off until they are required. The integrated accelerometer can be programmed to
interrupt the processor during a pre-defined shock/vibration event, this allows a low power usage
in typical “stop and go” mobile applications. Power to the GPS circuit can be switched ON and OFF
if a ‘cold fix’ is acceptable. If a ‘warm fix’ is required, providing 22 uA will allow GPS fixes in only a
few seconds.
4.1
Power Usage Profile
The ORBCOMM OG2 modem input voltage range allows for several battery chemistries and parallel
configurations.
Input Voltage:
6.0VDC to 15 VDC
Input Current:
Transmit Mode:
1.37 A @ 12VDC
Duration: typically <300ms, 700 ms max.
GPS On:
35 mA @ 12VDC
