Many thanks for your rely & guidance, having read the articles you
mentioned I have found the error of my ways!
I was using the latest Power SDR (version 1.10.4) from the flex
website which in softrock mode, does not allow the VFO to be moved
outside the tuning range of the fixed crystal installed.
Now having installed Guido's version 1.9.0 SRD40 all works well, I
can change the clock frequency, send the new value via CAT command to
VFO A and the tuning range moves there (exacly what I wanted), so no
need to change the centre freq. value in set-up!
Thanks again for your hep,
--- In firstname.lastname@example.org
, "Lyle Koehler, K0LR" <lyle@...>
> --- In email@example.com, "Lyle Koehler, K0LR" <lyle@>
> > If your Si570 is wired for parallel-port control and if you have
> > Guido's ExtIO_Si570.dll file installed where the software can
> > it,
> > the Si570 frequency can be controlled directly by PowerSDR v1.9.0
> > sr40
> > or Winrad. However, if you are using some external means of
> > controlling the Si570 such as a standalone microcontroller, you
> > need to enter the frequency in PowerSDR manually, just as if you
> > were
> > using a crystal-controlled SoftRock.
> > There is a folder called "Si570 Parallel Port Control" with some
> > very
> > basic information in the Files section of this group.
> Upon re-reading the excellent detailed instructions in Guido's
> PowerSDR-sr40 Installation Manual
> (http://powersdr-sr40.sourceforge.net/), I found that serial port
> control of an Si570 is also supported. (See "Controlling an External
> Oscillator" in the manual.) However, the serial port option
> microcontroller to forward the I2C commands. With parallel port
> control, no microcontroller is needed to talk to the Si570.
> Lyle, K0LR