[Lf] [Fwd: LF: G0MRF/SM6LKM DDS VFO and Jason]

[Andre Kesteloot]

Talbot Andrew wrote:

> >OK. It looks like we already have a standard. Andy, can you describe your
> protocol?
> I'll send it out under separate cover.
>
> >If we all clock our DDS chips with 5 or 10MHz from frequency standards, we
> >will have common "channels" although the numbers will not be nice (a lot of
>
> This is too prescriptive.  For instance, I am looking at a simple GPS
> locking scheme that will allow any frequency that is a multiple of 1Hz to be
> locked giving very good long term stability, but poor short term over a few
> seconds - suitable for long duration signalling purposes.  Using a
> 4.194304MHz is perfect for DDS synths as 'nice' frequencies occur
> automatically.  The step is 1/1024Hz so 1Hz steps and its subdivisions are
> exact
>
> >It is probably a good idea to make soft phase
> >transitions considering the huge reactive power that is circulating in the
> >antenna circuits at the QRO stations. Swiching phase 180 degrees
> >instantaneously in such a setup would be like throwing in the reverse gear
> >when driving forward at 100 MPH...
>
> A Tx with a guard circuit such as the Decca one can survive such abuse - the
> only real problems is an ethical one of switching sidebands - but a spike of
> a few 100s of microseconds, a function of the antenna bandwidth, every few
> 10s of seconds isn't going to annoy too many people.
>
> BTW, What's MPH in Sweden - or any other country outside the US/UK for that
> matter ;-)
>
> Andy  G4JNT
>
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