frequency steady, and move in steps, although I would prefer smaller
steps, around 20KHz. I like to see part of the previous looked at
signals. Personal taste, a little continuity.
On Fri, 2006-05-12 at 21:23 +0000, i2phd wrote:
> --- In [email protected], "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
> wrote:
> >
> > Alberto:
> >
> > I never did ask anyone about the offset clock frequency to the
> quad mixers you suggest for use with the Winrad software? Is it 12
> kHz such as the Soft Rock 40 suggest or 96 KHz in this case? It sort
> of came up in a discussion at soft rock group. I am ready to try a
> vfo design on my SR 40 v6 and want to know what I am getting into.
> >
> > ka9rza
>
> Well, there are two different ways of using an SDR program. One is
> like Flex does, choosing a fixed last IF, 11.025 Hz in their case
> (neglecting for a moment the anti-spur trick), and commanding the HW
> LO accordingly. Then the final conversion to zero IF is done in the
> software, together with demodulation.
>
> Another way is to have a wide last IF, as wide as the sampling
> frequency permits, e.g. from -48 to +48 kHz with 96 kHz sampling, and
> then tune inside this chunk the wanted signal, using a point-and-click
> technique in the software. Then the HW LO will need to jump in
> discrete steps of 96 kHz (or a bit less, to have some overlap). You
> see on the screen the entire chunk, the individual CW or SSB QSOs, and
> you choose which one you want to listen to. My personal preferences go
> to this way, and SDRadio and Winrad have been designed with this kind
> of utilization in mind.
>
> However nobody prevents you from using the first method with SDRadio,
> choosing whatever last IF frequency pleases you most. Just stay a bit
> away from the zero spot, to avoid the well known problems. 11025 Hz is
> a good choice as any other. And if you are intending to build a VFO,
> not a synthesizer, you are almost obliged to use the first method, as
> it would be a bit difficult to tune a VFO in discrete, all equal, steps.
>
> 73 Alberto I2PHD
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
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