> As fact, to test your FSK radio input, you can key the radio with no
connection, then
> short circuit the input and the frequency should shift. In other words,
if an open produces
> a mark tone, if you short the input, it will produce a space tone or vice
versa.
>
> I suppose that if there was a short in the interface transistor from base
to collector that
> the voltage directly from the COM port would be applied to the FSK input
and I suppose
> there could possible be some damage (I doubt it but you never know since
it's all PFM
> pure friggin' magic).
I built my first interface from the instructions provided with K6STI's RITTY
program. Brian described the basic 1 resistor, 1 transistor interface.
However, he also made some statements about how you could PROBABLY just
apply the com port Tx voltage, through the resistor, to the FSK input.
That's how I've made mine for 3 years now, using the FT-1000MP, IC-756PROII,
and the IC-706MKIIG. I've always used both the transistor and the resistor
for PTT and CW, from RTS and DTR, respectively.
For RTTY, I've used 2-conductor+shield cable from RS and stereo (2
cond+shield) jacks/plugs into and out of my interface box. That allows for
FSK/PTT, and in the interface box, I have a 1K resistor and 2N2222
transistor for the PTT line and just a 1K resistor for the FSK line. Never
a glitch! 73
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