Many thanks for the rapid and informative response Alan.
I'd just drawn out the circuit you described then found
the attachment later - doh !
The drawings were the same so your description was fine.
I've just printed them out and will further digest the info.
on my train journey home.
I am using a Clapp type xtal oscillator running at 2730 kHz nom.
(CW) and 2754 nom. (QRSS).
I then divide the oscillator frequency by ten and then by two:
136.5 nom. and 137.7 nom.
I'm switching the xtals and have a series of trimmers in series
with each one for discrete frequencies.
I may make one of the trimmers 'front panel mounted' for
versatility.
I use 'cwget' for my present QRSS activity, this set to a speed
of '2' which is about right for QRSS3.
I've just received your later drawing - many thanks.
The new TX/RX has been under construction for many months as
you know but is nearing switch on.
The receiver seems ok but there aren't too many stations to
listen to at present.
It has a 1400 kHz xtal filter with 750 Hz bandwidth.
I managed to obtain one of those semiconductor RF design books
that you recommended and am slowly plodding my way through it!
The TX is finished up to the driver stage so maybe this weekend
I may be able to stick some RF into the long wire !
No doubt your house lights will dim when I key down - HI!
73 Chris G3XIZ
-----Original Message-----
From: Alan Melia [mailto:[email protected]]
Sent: 22 September 2005 04:33:PM
To: [email protected]
Subject: LF: Re: DFCW (2...with cct)
Chris That is the hardware side You will find some software I think you
already use maybe has a sitable out put ?? QRSS from Rik Strobbe. One modem
line to PTT and one to indicated dots or dashes. This is a 0 to 5v signal
which will probably work with the circuit attached. I suggest try it before
going to the trouble of shifting the levels to avoid 0v as I suggested
earlier. The cap (trimmer) will probably need to be very small.
Cheers de Alan G3NYK
----- Original Message -----
From: "OSBORN, Chris" <[email protected]>
To: "LF Group (E-mail)" <[email protected]>
Sent: 22 September 2005 13:56
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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