Hi, Chris.
I use the program "QRS v4.02" from ON7YD to send both QRSS amd DFCW. It's
very easy to use and configure, and you can do useful things like alter the
inter-character spacings, flip DFCW mark and space, etc. You need to build a
1-transistor interface/level shifter to key the transmitter, but the circuit
is contained in the "Help" documentation that comes with the program.
http://www.qsl.net/on7yd/software_main.htm
If you can't get enough swing with a vari-cap, you can use a 1N918 or 1N4148
Si diode as a switch, and use it to switch a trimmer capacitor across the
crystal. I use a crystal in the 3MHz range in a Colpitts configuration, and
the DFCW control signal switches a 3-30 pF trimmer across the crystal. For
DFCW3 speeds, about 3 or 4 Hz shift is all you need. If you go to DFCW10 or
longer, you need only about 1 Hz or less shift.
The convention seems to be that the dash is the higher frequency.
73 Dave G3WCB IO1RM
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of OSBORN, Chris
Sent: 22 September 2005 13:57
To: LF Group (E-mail)
Subject: LF: DFCW
My new LF TX is nearly finished and I would like to add the option
of DFCW.
I was thinking of just placing a varicap diode in parallel with the
crystal and thus pulling the frequency
for achieving the dots / dashes.
Can someone direct me to a circuit diagram and software to achieve
this ?
73 Chris G3XIZ
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