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Message-ID: <2C18FDA91B0849C5958253F77FE7EF50@JimPC>
From: "James Moritz" <james.moritz@btopenworld.com>
To: <rsgb_lf_group@blacksheep.org>
References: <771416.76510.qm@web28105.mail.ukl.yahoo.com> <387288.17030.qm@web28509.mail.ukl.yahoo.com>
In-Reply-To: <387288.17030.qm@web28509.mail.ukl.yahoo.com>
Date: Wed, 7 Apr 2010 23:25:47 +0100
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Subject: Re: LF: WSPR without an SSB TRX ? 
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Dear Chris, LF Group,

----- Original Message ----- 
From: "Chris Osborn" <g3xiz@yahoo.co.uk>

...>My initial thoughts were that the PC is giving out a 1500 Hz tone + / - 
5 Hz.
This is used to generate USB signals from an SSB TX (?)
I was hoping to mix these tones with a stable frequency of 1400 Hz (say) 
ending up
with 100 Hz + / - 5 Hz - thence to an F-V converter - gain / level adjusted 
and thence
to the TX VCO input....>

That is probably feasible, if quite tricky - but much easier just to mix the 
1500Hz tone up directly to 500kHz to generate the VFO drive for your 
existing TX PA; that way only a simple fixed oscillator is required (one 
using a ceramic resonator would be adequately stable and "pullable" over a 
sufficient range). You then avoid all the business of having to calibrate 
the f/V gain, VCO frequency shift and so on. Plus, you can tune the 
frequency by changing the centre frequency setting in the software, and use 
it to transmit all sorts of other soundcard mFSK modes, RTTY etc.,  too.

Cheers, Jim Moritz
73 de M0BMU