[time-nuts] Measuring gpsdo vs itself

Hal Murray hmurray at megapathdsl.net
Mon Nov 5 05:06:18 UTC 2012


docdailey at gmail.com said:
> I guess what I am saying is if I discipline the counter with 10MHz and then
> measure the same 10MHz.  Just making sure we are on the same page. 

The input signal will be at a fixed offset from the reference clock.  That 
offset will depend on cable lengths.

If that setup gives a bad result, you know something doesn't work well.  If 
it gives a good result, I don't think you can assume it will work well with 
other input signals.


You might try using the GPSDO as the reference and measuring a typical 
crystal oscillator package.  They are usually quite stable short term.  Long 
term they track temperature.

Beware, some low cost oscillator packages have internal DDS.  Check the specs 
for jitter.  [I think the idea is to ship unprogrammed packages to 
distributors where they can be programmed to order and shipped with low 
turn-around-time.]

-- 
These are my opinions.  I hate spam.






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