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From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: LF: : Transcontinental modes - what next?
Date: Wed, 7 Mar 2001 10:17:20 -0000
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I was thinking of this aspect as well, for SMT Hell modesl.   Most
stations do not transvert, so soundcard output gives a problem.   
The parallel port is difficult, though not impossible, to utilise in
this way through Windoze so I cam to the conclusion that the serial port
is once again the optimum route.   It may mean constructing a bit of
hardware, but this need only be along the lines of a shift register/
latch and possibly a D/A converter to drive a varicap across a crystal.

Alternatively, one of the many serial D/A converters around now could
probably be driven directly from the serial port if this has its lines
toggled in a non-standard way to match the serial format needed by the
D/A - this may give Windoze software authors a headache but it can be
done.

The best route of course is just to use the serial port to control a DDS
- and HF-Instruments has now supplied around 100 suitable DDS modules.

Andy  G4JNT


> -----Original Message-----
> From: Alberto di Bene [mailto:dibene@usa.net]
> Sent: 2001-03-07 09:40
> To: rsgb_lf_group@blacksheep.org
> Subject: LF: RE: Transcontinental modes - what next?
> 
> 
> Hi all,
>           which would you all prefer as a way to 
> frequency-shift your TX ?
> With frequency shift I mean many steps, separated by a 
> fraction of an Hertz.
> The first two possibilities that come to my mind are an audio 
> output from the
> sound card (requiring then a mixer to bring the tone to the 
> wanted freq.),
> or a binary value output from, say, the parallel port, which 
> then would require
> a small external board with a DDS or a microcontroller to 
> drive the TX.
> 
> No linearity requirements will be needed. I need your input 
> to not start in a
> false direction.    TNX for any advices.
> 
> 73  Alberto   I2PHD
> 
> 
> 


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