[time-nuts] Datum TS2100 10MHz frequency drift

Esa Heikkinen tn1ajb at nic.fi
Thu Oct 29 16:41:15 EDT 2015

Philip Zahariev via time-nuts kirjoitti:

> Unfortunately I'm not happy with results because 10 MHz output signal
> after GPS lock (both leds on front "Locked" and "tracking" are "ON")
> has frequency drift (phase shift) with period around one second plus
> minus ~18 deg (+-5 ns) compared to other 10 MHz. I measure this by 2
> channel scope on 10 nS sweep, first channel connected to TS2100 10

Yes it works like that and it seems to update the DAC value once per 
second. Frequency wobbling is perfectly in sync with PPS output, which 
is kind of logical.

If you look TS2100 manual it says "stand alone time server" which means 
it's designed to serve as time standard - not as frequency standard. If 
you need stable frequency then you should try with Rubidium oscillator 
or with some other GPS unit. For example Thunderbolt has much more 
stable frequency output than TS2100, but it's also a timing receiver, 
not frequency standard.

However with OCXO and GPS upgrades you will get more than 10 times 
better timing than original TS2100. Without upgrades the TS2100 PPS is 
just below 1 microsecond, with MTI OCXO and Heol Design N024 GPS board 
it's about +-50 ns. So it's relatively good for every day timing 
purposes.. :)

Of course you could try could be to play with timing constant settings 
but I don't think it would help anything if the DAC is still written 
once per second. But if you find better values please let us know!

Best regards,


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