216
Transmission Modes
WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0
The bandwidth of the spectrum can be switched between 500 Hz, 1000 Hz, 4000 Hz and 24000 Hz. The
upper and lower frequency boundaries of the signal are the selected with the right and left cursors. With
the center cursor, the center frequency may be set more precisely.
The precision of the center fre-
quency is very important and directly influences the performance of the decoding
.
To ensure, that the system can handle drifting signals or a coarsely adjusted center frequency,
AFC
may
be enabled in the
Demodulator
menu. The carrier tracking function is now activated. If the deviation be-
tween the tracked and the adjusted center frequency is too large, the center frequency should be correct-
ed. The carrier tracking only works over a range of the center frequency ± 10 Hz.
The deviation of the adjusted center frequency and the tracked frequency is shown in the tuning display.
If a PACTOR-II signal was not found, the bar of the tuning display moves randomly. If a valid PACTOR-II
signal was detected, the bar is frozen during the entire frame and shows the deviation. Now the center
frequency may be manually adjusted to fit the correct frequency if necessary.
If a valid PACTOR-II signal was found the detected modulation type, frame length and the polarity is dis-
played. If it was an error free frame, the detected compression type, the status and the decoded text is
displayed.
Options | CRC Recognition.
The detected CRC is displayed in the decoder status bar, see “
” on page 39.
Using
Options | CRC Table
a certain CRC mask can be defined, see “
” on page 39.
Options | Auto Decrypt.
If enabled, the mode tries to calculate the key of encrypted connections. It may
take a few seconds until the key has been determined correctly. This function can not be used together
with CRC Recognition.
PACTOR-II-AUTO
Fully automatic switching between PACTOR-II (ARQ) and PACTOR-II-FEC may be achieved by selecting
PACTOR-II-AUTO
mode.
PACTOR-II-FEC
With PACTOR-II-FEC, a modern, narrow-band and reliable two-channel PSK mode is available, which co-
vers the needs of professional users for a secure and fast data transmission system. The good perfor-
mance during disturbances and a small bandwidth of 500Hz are achieved by the use of a two channel
DPSK modulation.
