Re: [Discuss-gnuradio] Testing crystal accuracy

[Jason Matusiak]

Thanks for the quick response Marcus!!!!

Since my Latex isn't very good (as in pretty much non-existent). Let me
see if I can rewrite what you recommended in my dumbed down language and
see if I am close.:

*I have two dongles, dongle 1 will be my modified dongle, dongle 2 will
be my un-modified dongle.

*Put a a known reference tone into each of the dongles where Ftune =
Fref - Foffset
** Foffset should be roughly a third of the sample rate
**An example at a sample rate of 1.024Msps would be a reference tone at
98MHz, and then tune the dongles to 97.659MHz

*I'll now see a baseband signal for both dongles whose offsets won't be
exactly the same.

*Multiple the resulting signals found above against each other (offset,1
* offset,2)
*Pass that through a LPF with a cutoff of Fsample/4, or 256khZ in this
case
**This will give the difference between the frequencies at frequency at
Foffset,1 +/- Foffset,2

*perform a QT freq sync or a quad demod into a QT time sink to compare.

Is that close?  I think I am missing something in there, and I have a
feeling that it has to do with the multiplication step as that makes the
least amount of sense to me.  Any way to enlighten me on what I am
missing above?  Thanks!