I have worked out a simple circuit that accurately converts 2Tone pseudo FSK
into a keying signal.
It uses a LP2950 5v regulator fed from a 7 to 15v supply, 74HC123 (dual
retriggable monostable), two NPN transistors (I used BC546) plus a handful
of C's and R's. Using stereo output from a sound card this will key two rigs
so ideal for SO2R.
In testing with 2Tone on my set up it produced a perfectly timed 45.45 baud
RTTY signal with 22mS long bit times, stop bit at 33mS and no timing jitter.
It will also work at 50 and 75 Baud.
However before I do a general release of the circuit, I need some people to
build the circuit and test it with their set up to ensure it is reasonably
hardware independent. It would be an idea if you had an oscilloscope to
ensure the keying signal is clean plus some electronic construction
experience.
The electronic components are about two US dollars. However the sockets, box
and board to build it on will cost a lot more. I built the prototype using
ugly construction on some double sided PCB off cuts.
If you could help please email me direct and I will send you the details. In
return I ask for your feedback on the circuit.
73 David
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