Wavecom W61PC V7.5.0 - Manual (Page 212)

202  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
PRESS-FAX
The transmission of press fax images on short-wave is based on gray levels and specific IOC values. A
number of IOC assignments were modified for press image transmissions. These special characteristics are
taken into account in the PRESS-FAX software.
Parameter Value
Frequency range HF
Operation modes Graphic mode, Broadcast
Center frequency 1900 Hz
Speed 60, 90, 120, 180 and 240 RPM, IOC 288, 352 and 576
Receiver settings FAX, DATA, CW, LSB or USB
Input format(s) AF, IF
If the Auto function is selected the software waits for the IOC identifier and synchronization sequence.
Both parameters are only transmitted at the start of an image and hence capture will only start when the
next image occurs. By selecting PRESS-FAX, the decoding starts immediately and the drum speed and
IOC can be programmed manually via the Drum speed and IOC items in the Demodulator menu. The
selected parameters are displayed in the decoder status bar.
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 cor-
rect 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
image to opens the Zoom menu, and select a color scheme from the bottom part. A checkmark is placed
to the left of the selection.
PSK-10
PSK-10 is a very narrow-band and reliable mode developed by F6CTE. The aim of this experimental slow
mode is to allow a chat-type communication between hams.
Parameter Value
Frequency range HF
Operation modes Simplex
Modulation DBPSK
Shift/Bandwidth 40 Hz
Symbol rate 10 Bd
Receiver settings DATA, CW, LSB or USB
Input format(s) AF, IF
Additional Info 10.148 MHz, 14.075 MHz
The baud rate is fixed at 10 Bd and is optimized to transfer the data rate, which an operator can input on
a keyboard by hand.
To separate the transferred characters, the sequence "011" is inserted between every character. Thus the
characters can be clearly separated, as long as no "011" sequence appears in the character itself. This was
taken into consideration when designing the alphabet.
To optimize the data throughput rate of the system, an alphabet with a variable character length is used.
For frequently used characters a symbol is used, which has a short word length (as is done with the Huff-
man compression). This alphabet is called Varicode and differs from the alphabet used in PSK-31.