Wavecom W61PC V7.5.0 - Manual (Page 247)

WAVECOM Decoder W61PC/LAN Manual V7.5 Transmission Modes  237
Parameter Value
Shift/Bandwidth 300 Hz
Symbol rate 81.3, 120.9, 123.5, 125 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info ITA-2
The unusual baud rate of 120.9 Bd is very typical for this mode. Synchronization is done at the beginning
of every burst transmission. The unencrypted calling sequence with tactical call signs has an autocorrela-
tion of 12 bits and all bits are interleaved. All traffic is encrypted. Occasionally operator chat in plain text
is transmitted.
WEATHER-FAX
A number of stations world-wide transmit weather charts on a regular schedule. During the transmission
of an image a characteristic and easily recognizable audio signal is heard. A specific frequency deviation
may also be seen on a tuning indicator.
Parameter Value
Frequency range HF
Operation modes Graphic Mode, Broadcast
Center frequency 1900 Hz
Speed 60, 90, 120, 180 and 240 RPM, IOC 288 or 576
Receiver settings FAX, DATA, CW, LSB or USB
Input format(s) AF, IF
Most transmitters work with a wide shift (± 400 Hz) and a few with narrow shift (± 150 Hz).
By selecting the Auto function, the software waits for the IOC identifier and synchronization sequence.
These signals are only transmitted once at the beginning of an image implying that capturing of the signal
will only take place at the start of the next image.
By selecting WEATHER-FAX the application starts immediately. The drum speed and the IOC may be en-
tered manually using the Drum speed and IOC items available from the Demodulator menu. The se-
lected values are displayed in the decoder status bar. In the short-wave band, weather charts are trans-
mitted almost exclusively with speeds of 60, 90 or 120 rpm. In the case of 60 rpm the drum rotates once
per second, for 90 rpm at one and a half time and for 120 rpm at a speed of twice a second. The index of
co-operation (IOC) is readily recognizable from the screen display when images are spread out too wide.
An IOC of 576 is mostly used on short-wave.
The decoder allows a continuous and smooth alignment of the image as it is being received from Op-
tions/Fine Speed. By using the Phase item in the Options menu the image can be shifted into the correct
position. Flip Left-Right and Flip Top-Down will reverse the image or turn it upside down.
To enhance the interpretation of gray-scale images, a false color option is available. Right-click on the im-
age to open the zoom menu and from the bottom part selects a color scheme. A checkmark is placed to
the left of the selection.
X.25
X.25 can be monitored in the VHF and UHF bands. This mode uses indirect FM (sub carrier) modulation.
Parameter Value
Frequency range VHF/UHF
Operation modes Duplex FEC TDMA