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1.Weather Charts via Short-wave (Marine Fax)
The transmission mode used for weather charts on short wave are
transmit line by line.
To correctly receive the chart you must have the same drum speed (RPM) (for correct
slanting), and the same index of co-operation (IOC) (for vertical resolution) as the
transmitting station.
Usual RPM speed is 120 with a IOC 576. RPM 60 and 90 are often in use by CIS stations,
also some Charts are transmit with a IOC 288.
Press Photo Fax transmissions use RPM 60 and IOC 352
Weather Charts on Short-wave are transmitted as Frequency Modulation
(FM).
That means that the transmitter is keyed between two frequencies, which 1500 Hz
corresponds for Black and 2300 Hz for White
For half tone (grey scale) Satellite pictures, the transmitter frequency shifted between
the frequency for black (1500 Hz) and the frequency for white (2300 Hz).
The difference/2 between the frequency for white and the frequency for black is called
Deviation. The standard deviation on Short-wave is 400 Hz (2x400=800 1500 to 2300 Hz).
For Long wave transmissions the standard Deviation is 150 Hz.
To receive Weather Charts on Short-wave you need a Single Side Band
(SSB) Receiver to receive the FM modulated audio Sub-carrier
Select the Upper Side Band (USB) and tune in the (carrier) frequency 1.9 kHz lower as
listed
The audio frequency output (Record/Speaker) is then fed to a interface or the Sound Card
input, that converts the different audio frequencies into digital format that can be
processed by the computer.
Automatic Picture Transmission (APT) is used to enable a fully automated unattended
reception of the transmitted pictures.
At the start of the transmission a start tone is transmitted for some seconds, which is
recognised by the receiving unit.
At the end of the transmission a stop tone is sent that switches the receiving unit back
to standby mode.
Weather Charts have only Black and White contours, for good resolution 2 Bit decoding
is the best way for clear charts
SATELLITE REBROADCAST ON HF SHORTWAVE TIME STATION
FREQ_1 FREQ_2 FREQ_3 FREQ_4 FREQ_5 FREQ_6 ---------------------------------------------------------------------
0030 Honolulu Meteo 9982.5 11090 16135 23331.5
0045 Honolulu Meteo 9982.5 11090 16135 23331.5
0100 CF Halifax 122.5 4271 6496.4 10536 13510
0110 Tokyo Meteo 3622.5 7305 9970 13597 18220 23522.9
0120 Tai-pei Meteo 4616 5250 8140 13900
0248 USCG San Franci 4346 8682 12730 17151 22527
0259 USCG San Franci 4346 8682 12730 17151 22527
0301 CF Halifax 122.5 4271 6496.4 10536 13510
0351 USCG Boston NMF 6340.5 12750
0512 Delhi Meteo 4993.5 7403 14840 18225
0630 Honolulu Meteo 9982.5 11090 16135 23331.5
0645 Honolulu Meteo 9982.5 11090 16135 23331.5
0700 Seoul Meteo 5385 5857.5 7433.5 9165 13570
0710 Tokyo Meteo 3622.5 7305 9970 13597 18220 23522.9
0720 Tai-pei Meteo 4616 5250 8140 13900 0908 USCG San Franci 4346 8682 12730 17151 22527
0944 USCG San Franci 4346 8682 12730 17151 22527
0951 USCG Boston NMF 6340.5 12750
1001 CF Halifax 122.5 4271 6496.4 10536 13510
1230 Honolulu Meteo 9982.5 11090 16135 23331.5 1245 Honolulu Meteo 9982.5 11090 16135 23331.5
1310 CF Halifax 122.5 4271 6496.4 10536 13510
1310 Tokyo Meteo 3622.5 7305 9970 13597 18220 23522.9
1320 Tai-pei Meteo 4616 5250 8140 13900
1438 USCG San Franci 4346 8682 12730 17151 22527
1449 USCG San Franci 4346 8682 12730 17151 22527 1503 USCG Boston NMF 6340.5 12750
1830 Honolulu Meteo 9982.5 11090 16135 23331.5
1845 Honolulu Meteo 9982.5 11090 16135 23331.5 1900 Seoul Meteo 5385 5857.5 7433.5 9165 13570
1910 Tokyo Meteo 3622.5 7305 9970 13597 18220 23522.9
1920 Tai-pei Meteo 4616 5250 8140 13900 2108 USCG San Franci 4346 8682 12730 17151.2 22527
2151 USCG Boston NMF 6340.5 12750
