1200 Bit/s BPSK AX.25 soundcard demodulator

Warbler is a piece of software made by Wouter Jan Ubbels (PE4WJ) which can be used to demodulate a 1200Bit/s AX.25 BPSK signal (e.g. from AMSAT-OSCAR 16/PACSAT or ITAMSAT-OSCAR 26), using the PC’s soundcard. Here’s a screenshot, showing
PACSAT (AO-16) downlink.

Warbler Screenshot

Operating instructions

Warbler expects an audio signal with a carrier frequency between 1400 and 1800Hz. Limited Doppler correction is provided within this range. Connect the audio output of your SSB transceiver / receiver to the line or microphone input. Set the audio level such that the “Audio Level” bar is in the green range. The Costas loop will now attempt to lock onto the received signal, in case of lock, the “Sync” flag is displayed in green. Recovered carrier frequency is displayed by the slider and in numerical form. By default, the AX.25 INFO field is displayed in ASCII. By checking the “Display INFO in HEX” checkbox, it will be displayed in Hexadecimal notation. Warbler logs to a KISS file named “warbler.kss”, in the directory from which Warbler is run (usually the “\dist” directory). Warbler appends all received frames to this file every time the program is run. Another file, named “warbler.asc” is also created, this is for a future implementation of logging to an ASCII file. In the current version, nothing is written to this file.

Installation instructions

Warbler requires you to have the latest JAVA Runtime Environment (JRE) installed.

To run Warbler, unzip the file, open the “\dist” directory and double-click the “warbler.jar” file


Download Warbler v1.0.3 Beta version
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Source: Original article PE4WJ