Hi Alberto,
I too noticed the frequency was not spot on and it increased a little at
start-up, but this is perhaps not surprising when you bear in mind the means
of generation and its age. In fact I am surprised that they can be as
accurate as they are.
Probably the Sound card error is a combination of actual with card error. It
is normally necessary to spend some time calibrating one's receive path,
including the sound card, before it is possible to accurately measure the
transmitted frequency.
73, John, G4CNN





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