Wavecom W61PC V7.5.0 - Manual (Page 50)

40  First start WAVECOM Decoder W61PC/LAN Manual V7.5
SUBTONE
The same as DSP, but the parameters are optimized for low frequencies.
PB Center...
Click on the PB Center menu item to adjust the center frequency of the passband filter.
For more details see “ Passband Filter Support ” on page 65.
PB Bandwidth...
Click on the PB Bandwidth menu item to adjust the bandwidth of the passband filter.
For more details see “ Passband Filter Support ” on page 65.
Center...
Click on the Center menu item to adjust the demodulator center frequency within 1 Hz accuracy. For
modes utilizing direct FSK this button is not available: in this case the offset frequency is equal to the ef-
fective center frequency.
Shift...
Click on the Shift menu item to adjust the frequency shift in 1Hz steps. In HF modes the range is 50 Hz –
3500 Hz, and in VHF-UHF modes using direct FSK the range is 50 Hz – 16000 Hz.
Baudrate...
Click on the Baudrate menu item to enter a new value. Depending on the mode, the baud rate dialog box
contains preset values which may be directly selected. The new value is selected by double-clicking on the
preset value or clicking on OK.
Polarity...
Click the Polarity menu item to toggle between normal and inverse polarity.
Offset...
Adjusting the offset frequency and the center frequency will adapt the decoder input to a receiver IF out-
put.
The minimum offset frequency resolution available with the decoder is 1 Hz. The effective center frequen-
cy is the sum of the offset frequency and the center frequency. The function is similar to the mixing of the
signal frequency and BFO of a receiver.
An exception is the FFSK demodulator for direct frequency modulation: in this case the indicated offset
frequency is equal to the effective center frequency.
An example for an HF receiver and ARQ-E mode:
 Receiver IF 455,000 Hz
 Offset 453,300 Hz
 Center 1700 Hz
The advantage of this method is that the user only needs to know the center frequency.
Another example for a VHF-UHF receiver and POCSAG mode:
 Receiver IF 455,000 Hz
 Offset 455,000 Hz
 Center 0 Hz
In this case the offset frequency is equal to the center frequency.