[time-nuts] GPS: ADEV or MDEV?

Angus not.again at btinternet.com
Sat Apr 21 07:02:26 EDT 2007



>The VP is still distinctly worse until tau > 1000sec.
>
>The plots are not conclusive evidence that correcting for the sawtooth 
>error isn't advisable.
>What about "hanging bridges" and similar artifacts?
>
>Bruce


It would be interresting to see exactly how much the sawtooth on an
M12 affects actual GPSDO setups. 

I made a hardware sawtooth remover a couple of years ago as an
experiment, but where I used it I didn't seen much difference. I just
checked again recently, but the sawtooth errors seem very small
compared to overall instability, even for just an M12 to Rb at a
fairly stable temperature. The larger errors of a few ns (over 1000s)
which are occasionally visible when the M12 is temperature controlled
seem regularly to be exceeded by other instabilities in the pps
output.

There are plenty of times when sawtooth removal would be of
use/interest, but in a typical GPSDO which has a heap of other errors,
I do wonder what improvements in performance would actually be seen in
the output from the oscillator - which is all that a lot of people are
really interrested in.

Angus.





More information about the time-nuts mailing list