Running WSPR and WSJT with VOX-type PTT under Linux

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oz1pif
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Running WSPR and WSJT with VOX-type PTT under Linux

This has only been tested on Ubuntu 8.10 with a strong likelihood of being true for other Linux's as well. What the situation is in Windoze land I wouldn't know.
The facts are: you can't just leave "PTT Port" empty, as the programs won't Tx in that case, something needs to be entered that looks sufficiently like a serial port to satisfy the PTT function of the program. Since the ports of WSJT and WSPR I've dealt with for Linux already had "/dev/ttyS0" in that field, and they "worked" even though there was no actual HW behind that, everything looked healthy to me. (I'm using a SignaLink USB since I'm using (mostly) a computer with no built-in RS-232c ports, I could use a USB<->RS232C converter at the price of adding to the cable fest, but I choose this route instead)

If you want to know how to modify the SignaLink USB to decent specifications look here: http://www.frenning.dk/OZ1PIF_HOMEPAGE/SignaLinkUSB-mods.html

The thing which has been giving me the willies, is that either program would invariably fail after a longer (several hours) or shorter period of time - shorter if a failure has already happened on the boot of the OS. Failure mode is invariably "address out of bounds in array indexing".

This finally let me onto the theory that although the kernel would accept the port manipulation commands, it would just stack them away somewhere until it couldn't handle any more, whereupon the application would be given a bogus reference and wham.

I then tried an old trick from my Unix days: in every *nix like OS there is a "/dev/null" device, a character device that can't ever overflow, because all commands and data sent to it are immediately discarded, "sent to the grounding rod" so to speak.

I'm happy to report that WSPR has just survived my 24 hour torture test (25% Tx/Rx ratio), using "/dev/null" as the bogus "PTT Port", and that I've just started the same test of WSJT7 in WSPR QSO-mode.

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Vy 73 de OZ1PIF/5Q2M, Peter

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