Wavecom W-SPECTRA (Automatic Monitoring System) V1.1.0 - Manual (Page 147)

WAVECOM Monitoring System W-SPECTRA, W-SPEED Manual V1.1.0 Transmission Modes
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The orbiting satellites may be received with an active antenna and a high quality VHF-UHF receiver. An
optimal receiving station allows reception for approximately 20 minutes before the satellite has moved be-
low the horizon. The AF output of the receiver may be fed directly into the decoder, which converts it into
a weather image viewing station providing excellent image quality.
Polarization problems occur with orbiting satellites resulting in reception gaps of up to 2 minutes. A special
antenna may alleviate this problem.
Due to the Doppler effect the frequency of the received signal may change as much as 1000 Hz during the
reception period. The receiver should therefore have a built-in automatic frequency control (AFC) capabil-
ity.
NWR-SAME
NWR is the abbreviation for NOAA (National Oceanic and Atmospheric Administration [USA]) Weather Ra-
dio All Hazards, which is operated by the NWS (National Weather System). A similar system using the
same message format is operated as weather radio Canada by the Meteorological Service of Canada.
Parameter Value
Frequency range VHF/UHF
Operation modes Broadcast
Modulation FM, SUB FSK
Center frequency 1822.9 Hz
Shift 800 Hz
Symbol rate 520.83 Bd
Receiver settings FM
Input format(s) AF, IF
SAME is the abbreviation for Specific Area Message Encoding.
This feature is incorporated in information regarding severe weather conditions, which is distributed by the
NWS. The area to which such a message applies is restricted by the area code, thus avoiding false alarm
in areas which are not affected by the weather condition which causes the alarm.
The coded message is transmitted, using Audio Frequency Shift Keying, on the audio channel of the NWR
transmitter system. Seven channels on 162.400, 162.425, 162.450, 162.475, 162.500, 161.525 and
162.550 MHz are assigned to this task.
The baud rate is 520.83 Bd the mark frequency is 2083.3 Hz and the space frequency 1562.5 Hz, all val-
ues fixed.
The user cannot change the audio frequency by tuning the receiver.
For this reason the center frequency is preset, as well as the baud rate.
The display shows the information of the messages split into its meaningful parts.
A message contains a preamble (sync word), a data header part, an alert tone signal (if applicable), a
voice message part and an end-of-message part. The data part format is as follows:
ZCZC-ORG-EEE-PSSCCC-PSSCCC+TTTT-JJJHHMM-LLLLLLLL
ZCZC Start-of-message header block code
ORG Originator header block code
EEE Event header block code