[Lf] G0MRF/SM6LKM DDS VFO and Jason]

[Andre Kesteloot]

Johan Bodin wrote:

> Larry VA3LK wrote:
>
> > Please, for serial protocol just use what Andy has already done or do the
> > exact same functions, Integer steps at the limits of the DDS chip.
>
> OK. It looks like we already have a standard. Andy, can you describe your protocol?
>
> > The worst result for me would be doing something like 10 milliHz steps,
> > which again would be not quite 10 milliHz for those with different
> > Reference oscillator frequencies.  The use of a second DDS to make a nice
> > round integer clock for a DDS would be the best solution but is overly
> > costly at the moment.
>
> 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
> ugly decimals). The 10MHz guys (including me) will only have access to
> half the number of "channels" because of the doubled step size... However,
> 901943 "channels" on the 136kHz band is enough for me :-)
>
> > PS, one final point, I would implement a trigger input on the PIC as well
> > so that one can easily make the whole DDS setup coherent to a 1 Second
> > resource as well.  I have that here now on the BPSK and it could be used to
> > squeeze a bit out of the system.....
>
> Yes, I am thinking about a way to implement this in the new software for the
> G0MRF DDS board. 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...
>
> 73
> Johan SM6LKM