Wavecom W61PC V7.5.0 - Manual (Page 204)

194  Transmission Modes WAVECOM Decoder W61PC/LAN Manual V7.5
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 “ CRC Recogni-
tion ” on page 30.
Using Options | CRC Table a certain CRC mask can be defined, see “ CRC Table ” on page 31.
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.