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Hi Peter and all,
Am 28.02.2014 16:21, schrieb PA1SDB, Peter:
Hello VLF.
Just a experience message !
It seems that there is somewhere a
perfect setting in "Width of FFT-bin", but where ?
A good question.. and not easily answered. I'd say "it all depends".
In this case, it depends on the soundcard's oscillator stability,
despite stabilisation from the GPS sync pulse.
At 16 uHz frequency we seem to have reached a limit (for this type
of oscillator drift compensation).
The next logical step would be building an A/D converter, or
modifying a USB audio device to take the samping clock directly off
a low-noise 'rock-solid reference' (a good GPS disciplined OCXO for
example).
I have fragments for such a project laying on the workbench (a
low-cost Cortex-M3 microcontroller development kit) but no time yet
to put the bits (bytes) and pieces together.
At least, one would know of the Ionosphere (stability of the path
length) or whatever else is the limiting factor.
GL and all the best,
Wolf .
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