Folks,
I find it difficult to understand why one would want to generate DFCW with
up-down buttons, when there are plenty of ways to do it reliably with audio.
It would be quite trivial to write a BASIC program that generated sound out
the PC speaker, and of course sound card methods would be straight-forward
to one of the Windows programming experts. A few years ago I wrote a DOS
program which does this type of thing.
I have three other suggestions: First, build my LF Exciter (see
www.qsl.net/zl1bpu) and use the direct output to drive the mic input of the
rig via an attenuator. This output is flat down to DC, and you can easily
set up a beacon script to send DFCW at an audio frequency (say 1kHz) rather
than at LF. The Exciter runs many modes, which can be mixed in the script.
There is also a real-time PC program for the Exciter which will control it
in all the available modes. The Exciter now includes a new DFCW variant I
call 'Castle' which is about 20% faster for the same dot duration (needs no
inter-element spaces at all).
If you are lucky enough to have one of those nice little FEI Rubidium
Synthesizers (FE-5650A), I have a PC control program which allows you to
send DFCW, Castle, S/MT-Hell and any other ASK or FSK mode you care to
invent all the way from 5kHz to 20MHz.
The other possibility is to use the method Jim suggested, but instead of
using UP/DOWN controls, use the voltage from the DTR to change the frequency
of a VCO. I'd recommend a sine-wave design such as one of the function
generator chips, but even a venerable 555 would do. It has a pin designed
for frequency modulation.
73,
Murray ZL1BPU
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