Wandjina - A software implementation of Frequency Difference Keying (FDK) suitable for HF paths
First entry 03/12/01 - Last update 03/05/08
General Philosophy of Wandjina (FDK for HF):-
Looking at the characteristics of VFSKCW signals transmitted from here in VK and received in the US, I considered that a special variation of FDK would be suitable to allow transmission and reception of beaconing signals over that path. The signals showed considerable smearing from multi-path and unstable path lengths also causing a doppler effect on the signals.
The Wandjina software had been developed to the point where it has been used to decode 2mW Wandjina transmissions emanating from Sydney Australia and received in the US.
The software is still under development (some 6 years later...) including tidying up dialogs, re-vamping of the Auto variant of the SmartScan algorithm and inclusion of a Wandjina beacon message WAV file generator.
The variant of Wandjina used on 22m band uses the output of the excellent spectrographic program by Alberto di Bene called Argo. There is a function in Argo which allows the saving in *.CSV format (used by spreadsheets) of the output of the FFT function. Argo is set to a 'Mode' of 3 second dots (and usually a speed of normal or slow). The logging function is set to '1 second'.
Argo is usually set to do a run during the expected time for a propagation opening (for the VK - US trip this is about 0600 - 1330 UTC on 13Mhz) and the logging function enabled. After the logging run is completed the output file is then converted by Wandjina to its native binary format. Wandjina can then display or decode the file to extract the Wandjina mode signal and output the resulting message.
Below click on thumbnail and see a screen shot of Wandjina which has decoded a *.CSV file sent to me from Lyle Koehler (K0LR) who received my 2mW Wandjina signal in Minnesota USA (14509kms).
At a later date the decoding software was sent to Lyle and the decoding was done at the US end for the same result.
Wandjina Character Coding
See Table below for encoding of characters in terms of the difference (in Hz) between the two tones.
| SPACE | 6.8 |
/ |
5.3 | > | 3.8 | M | 2.3 |
| ! | 6.7 | 0 | 5.2 | ? | 3.7 | N | 2.2 |
| " | 6.6 | 1 | 5.1 | @ | 3.6 | O | 2.1 |
| # | 6.5 | 2 | 5.0 | A | 3.5 | P | 2.0 |
| $ | 6.4 | 3 | 4.9 | B | 3.4 | Q | 1.9 |
| % | 6.3 | 4 | 4.8 |
C |
3.3 | R | 1.8 |
| & | 6.2 | 5 | 4.7 | D | 3.2 | S | 1.7 |
| ' | 6.1 | 6 | 4.6 | E | 3.1 | T | 1.6 |
| ( | 6.0 | 7 | 4.5 | F | 3.0 | U | 1.5 |
| ) | 5.9 | 8 | 4.4 | G | 2.9 | V | 1.4 |
| * | 5.8 | 9 | 4.3 | H | 2.8 | W | 1.3 |
| + | 5.7 | : | 4.2 | I | 2.7 | X | 1.2 |
| , | 5.6 | ; | 4.1 | J | 2.6 | Y | 1.1 |
| - | 5.5 | < | 4.0 | K | 2.5 | Z | 1.0 |
| . | 5.4 | = | 3.9 | L | 2.4 |
Last updated Sunday, 11 May 2008