AX25 Decoder

 

Availability

SkySweeper Lite : NO
SkySweeper STD : YES
SkySweeper STD+ : YES
SkySweeper PRO : YES

 

General Description

The SkySweeper AX25 (packet) decoder has two main operational modes (300 baud (HF) and 1200 baud (VHF). SkySweeper AX25 decoder doesn’t support the automatic tone search. So, the frequencies for space and mark has to be set manually. In 1200 baud (VHF) mode the tones are typically located at 1200 Hz and 2200 Hz (shift 1000 Hz). In HF mode the tones can be located more randomly, but the shift is typically 200 Hz.

In AX25 you can set the lower frequency by double clicking the mouse on the required frequency position, and then SkySweeper allows you to set a second (=higher) frequency, that can be set by a mouse click. The values of frequencies and the frequency offset are also shown on the screen.

 

'Lock' is not used in AX25 (the tones stay where they are, because there’s no automatic frequency search). ‘Reset’ resets the decoder and the received text can be saved by using ‘Save’. The parameters can be modified by pressing the ‘Config’ button.

 

SkySweeper supports both FFT and waterfall display modes for decoder tuning. The Decoder Spectrum Dialog chapter gives more information about spectrum display options.

Parameters can be modified by pressing the ‘Config’ button. Note: you can install several decoders in one configuration, if required.

 

Configuration

Pressing the ‘Config’ button opens the following Configuration dialog box.

 

 

Parameters

 

Baud Rate

This selects the baud rate: 300 baud (HF) or 1200 baud (VHF)

 

Print Raw Data

The received raw data (data without protocol information) print format can be selected from four options:

'Binary' prints the data as bits

'Hex' prints the data in hex format

'Decimal' prints the data in decimal format

'Characters' prints the data in character format

 

Decoded Frame Types

The AX25 packet frame types to be decoded can be selected. The possible choices are: Information, Supervisory and Unnumbered frames.

 

Decoded Frame Fields

The decoded fields in a frame can be selected from six options:

'Flag' fixed character in the start and end of the packet

'Address' call signs of source and destination etc

'Control' frame type information

'PID' the protocol type

'Info' user data

'FCS' frame check sequence

Field Number Print Format

This selects the print format of field numbers (hex/decimal).

Control Field Mode

This is the length of control field (8 or 128 bits). The most common value is 8.

 

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.