Wavecom W61PC V7.5.0 - Manual (Page 87)

WAVECOM Decoder W61PC/LAN Manual V7.5 Analysis Tools  77
The software proceeds to create a list of modes to check, which is displayed in the Code Check window.
The content of this list depends on the selection of the Fast Scan or Full Scan options.
 In Fast Scan mode, the list only contains the modes which are known to use the measured baud
rate, to reduce the evaluation time.
 In Full Scan every mode which is suitable for an FSK code check is listed, and all possible combi-
nations are checked.
FSK Code Check DIR
FSK code check is started in automatic mode by selecting the Analysis | Code Check button or from
VHF/UHF-DIR | Analysis | FSK Code Check. This function has a high degree of accuracy when deter-
mining baud rate, frequency shift and center frequency of HF FSK systems.
As an additional help FSK code check also offers an option to start the analysis manually after user entry
of baud rate, frequency shift and center frequency. To utilize this option the Auto button must be dese-
lected. The software will then start data acquisition using the pre-selected parameters. If a pre-selected
parameter has been changed data acquisition is atomatically restarted.
The selection of baud rate, frequency shift or center frequency is done by clicking on the status bar fields
or using the Demodulator menu.
If the FSK code check cannot identify a mode, the code check should be repeated. Data acquisition is con-
tinuously performed as a background task. Heavy fading or other disturbances during data acquisition
may prevent the identification of a mode.
You can also restart data acquisition by pressing the Resync button.
Because this kind of signal is not continuous, there is a need for a Noise Gate. The status of the noise
gate is displayed in the status bar; it examines the input signal and tries to determine if a valid signal is
available which can be processed, or if the input consists only of noise.
Steps:
 After starting the FSK code check the frequency shift, center frequency and the baud rate are de-
termined. The values of these parameters are displayed in the appropriate fields after the meas-
urement has completed.
 The software then proceeds with code and system analysis. The incoming bit stream is tested and
compared against known modes.