[Linrad] Re: Linrad and MAP65-IQ Calibration

[Leif Asbrink <sm5bsz.com; leif@xxxxxxxxxxxxxxxx>]

Hi Guy,

> I would like to understand this properly before I start making
> changes!
> If I have understood you correctly, I first need to set
> SDR14_SAMPLING_CLOCK
> in sdrdef.h (and recompile) to correct the Linrad reading.
There is another option. You may use SpectraVue to change
the contents of the non-volatile RAM inside the SDR-IQ.
I never did that and I do not know what effects it would
have, but most likely it would be equivalent to change
SDR14_SAMPLING_CLOCK

> Then I need to set Fcal in MAP-65-IQ to bring that into line.
> Is this correct?
I actually do not know the details of MAP-65, but once
Linrad shows the frequency correctly any frequency shift
must be taken care of inside MAP65-IQ. There is Fcal and 
Fadd. Presumably you could also adjust Fadd.

> If this is the right approach, then may I request that the next
> version of Linrad
> brings the sampling clock frequency out into the setup in some form,
> perhaps just as correction of up to +/-1000Hz if that is enough.
> Recompiling is ok, but it needs to be done for every new version of
> Linrad,
> and there are lots of SDR-IQ users out there who would not wish to do
> that,
> but who would like to correct this sampling frequency error.
Try to run the SpectraVue calibration. In case it makes the
SDR-IQ behave as if the sampling speed were exactly 66.6666666 MHz
and thus makes both SpectraVue and Linrad correctly calibrated
it would be better to leave caligration outside Linrad.

73

  Leif


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