General description
The PACTOR decoder supports the listen mode for both PACTOR-1 ARQ and FEC transmissions. The Huffman coded and 8-bit ASCII coding is supported (Huffman set as a default).
ASCII coding is normally used in selective calls and Huffman coding in other types of PACTOR transmissions.
The decoder uses the most modern digital PLL synchronization technology for bit synchronization and neural network for detection and prints characters on the screen. It searches the PACTOR transmission in the range of the given frequency boundaries. Also you can set the the first FSK frequency by doubleclicking mouse on the wanted frequency position and then SkySweeper allows you to set the second frequency (can be set by the mouse click). The numeral values of frequencies and the frequency offset are shown also in the screen. When PACTOR transmission has been detected in the given range, the decoder will then lock itself to that frequency. When locked, the decoder draws the bolded blue line on the spectrum display on the currently locked frequency. If the decoder is not locked, then the blue line is not shown as bolded. After locked the frequency the decoder starts to estimate the keying parameters of the transmission. When all the parameters have been estimated then the decoder starts to print characters on the screen. In the locked state, the carrier frequencies are automatically monitored in the given frequency boundaries and if the carrier frequency changes, then the decoder moves to a new frequency. If 'Lock' is pressed in the user interface, then decoder will not automatically change it's frequency. ‘Reset’ resets the decoder and received text can be saved using ‘Save’. The parameters can be modified by pressing the ‘Config’ button. Note, that you can install several decoders in one configuration if needed.
Configuration
Pressing the ‘Config’ button opens the following configuration dialog.
Parameters
Mode
With this switch you can select the coding to be received (Huffman/ASCII). If needed, you can add two PACTOR decoders in your configuration (other decoding ASCII and another decoding Huffman).
Tone scan area
The PACTOR transmission has two tones mark and space. The scanned frequency range for mark and space will be given with two values low and high. The mark and space tones are searched only inside this frequency window.
Offset
If fixed offset check box is selected the user can give the fixed frequency offset between mark and space carrier frequencies. The fixed frequency offset is used in automatic scanning mode. In PACTOR fixed offset has 200 Hz as a default value.
FFT
The FFT button opens and closes the power spectrum window. You can for example close the power spectrum window when the decoder has locked into correct frequency in order to get more space for text window
Save
The save button opens the log file control dialog, which is used to open or close a log file. The detector text window can be also saved into file or sent into socket.
Lock
The lock button locks or unlocks the decoder frequency. Decoders have the automatic frequency scanning feature. Push the lock button when you want to lock decoder into selected frequency. Push Un-Lock button when you want to release the frequency locking.
Reset
The reset button resets the decoder and clears the text window.
