Wavecom W61PC V7.5.0 - Manual (Page 198)

188  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
Parameter Value
Submodes 250 Hz / 8 Tones / 31.25 Bd
500 Hz / 8 Tones / 62.5 Bd
500 Hz / 16 Tones / 31.25 Bd
1000 Hz / 32 Tones / 31.25 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info 7038.5 MHz, 10133.65 MHz, 14075.65 MHz, 14107.5 MHz,
18102.65 MHz, 21086.5 MHz, 28076.0 MHz
Olivia focuses on robustness against signal-path disturbances, especially fading and multipath propaga-
tion. This requirement results in a low data-throughput and in a standard configuration five characters are
merged into one block and transferred in two seconds, i.e., 2.5 characters per second.
The signals are MFSK-modulated, mostly with a baud rate of 31.25. In this way all transmitted energy is
concentrated in a single tone of relatively long duration.
The standard center frequency depends on the chosen bandwidth, i.e. it is 500 Hz plus half of the selected
bandwidth. The user can tune the receiver so that the signal has a center frequency according to the
standard, or change the center frequency manually. The bandwidth can be changed manually as well.
The polarity of the signal is being detected and the demodulator set accordingly.
For each character a confidence value is calculated and evaluated. Data with a confidence value of at least
90% are displayed in black, with a confidence-value of at least 50% they are shown in red - otherwise a
red underline character is displayed. A block with a confidence value of less than 75% is not shown at all.
ORBCOMM
The ORBCOMM System is a wide area, packet switched, two-way data communication system. Communi-
cations to and from Subscriber Communicators (SC) to ORBCOMM Gateways are accomplished through a
constellation of Low-Earth Orbit (LEO) Microstar satellites. ORBCOMM Gateways are connected to dial-up
circuits, private dedicated lines or the Internet.
Parameter Value
Frequency range VHF, 137 – 138 MHz
Operation modes Downlink to Subscriber Communicator
Modulation SDPSK
Symbol rate 4800 Bd
Bandwidth 10 kHz
Receiver settings FM BW = 15 kHz
Input format(s) IF
The ORBCOMM System consists of a Network Control Center (NCC) that manages the overall system
worldwide and three operational segments:
 a space segment consisting of 36 LEO Satellites
 a ground segment consisting of Gateway Earth Stations (GES) and control centers located
throughout the world
 a subscriber segment consisting of communicators used by ORBCOMM System subscribers to
transmit and receive information to and from the LEO Satellites.
RF communication within the ORBCOMM System operates in the very high frequency (VHF) portion of the
frequency spectrum between 137 and 150 (MHz). The ORBCOMM Satellites have a subscriber transmitter
that provides a continuous 4800 bps stream of packet data. Each Satellite also has multiple subscriber re-