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LF: RE: DFCW

To: [email protected]
Subject: LF: RE: DFCW
From: "Dave G3WCB" <[email protected]>
Date: Thu, 22 Sep 2005 21:12:23 +0100
Delivery-date: Thu, 22 Sep 2005 21:13:55 +0100
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In-reply-to: <B333AB0EF6D4D4118BAF00508BAED8EA088DA778@mms12014.stv.uk.astrium.corp>
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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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