Here is the latest on PSK-31 on a Pocket PC


Hi gang.

I made progress on my PSK31 on PocketPC project. See the screenshot:

The program displays a waterfall between 1 and 3 kHz in the upper part of the screen and received text in the lower part. The received frequency is set to 2kHz and it could not be changed now. AFC does not work either.

I have compared my demodulator against MixW32, TrueTTY, WinPSK31 and Zakanaka. I used WSCGen from ae4jy to generate testing signal burried into noise, . I was quite surpirised by performance of the listed programs. The best worked Zakanaka. The programs were run side by side on my PC. MixW32, TrueTTY and my program on PPC work a bit worse than Zakanaka, but still good enough. The worst was WinPSK, which is striking, because its algorithms are supposed to be most advanced. The reason could be different sampling rates of sender and receiver. I please the authors of the named programs not to take it as an offense. Maybe someone else could repeat the testing?

Anyway. The program is based on two linux projects: GMFSK by Tomi Manninen OH2BNS and twpsk by Hansi Reiser DL9RDZ . They both are based on the legendary code from Peter G3PLX, the inventor of PSK31.

I rewrote the PSK31 decoder of GMFSK to fixed point arithmetics. A bit of floating point arithmetics is still used for precalculations, but not for waterfall (FFT) or decoding. The load of my rusty IPaq 3600 is 30%.

If you want to test the program yourself, send me an e-mail. I will be glad to receive reports of decoder quality and compatibility problems. I am willing to share the source, but I would like to make a clean skeleton without the bells and whistles.

I will work now on frequency selection by clicking on the waterfall, on spectrum display and on AFC.

73, Vojtech OK1IAK