[time-nuts] Fw: Optical transfer of time and frequency

[Tom Van Baak]

Hal,

> How close could you get if you brought two of them together, compared phase, 
> drove them to the site for a nights work, drove them back to the same 
> location and compared the phase again.

That's essentially asking what the ADEV (or, TDEV) is for tau 1 day. Rb isn't near good enough. Neither is Cs, for that matter.

See www.leapsecond.com/tmp/5071a-12-run8-5d-10d.gif for a plot of a bunch of 5071A Cs clocks. They are compared together for 5 days to determine their relative phase and frequency offsets and then go on a 5-day trip. You can see how the phase drifts as random walk does its thing. It's way more than 500 ps per day.

That's why the OP cannot use free-running clocks. He needs some method to actively keep them in tight phase lock or passively compare them to within 500 ps in order to adjust the timestamps in post-facto.

/tvb

----- Original Message ----- 
From: "Hal Murray" <hmurray at megapathdsl.net>
To: "Tom Van Baak" <tvb at leapsecond.com>; "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Cc: <hmurray at megapathdsl.net>
Sent: Wednesday, May 04, 2016 10:30 AM
Subject: Re: [time-nuts] Fw: Optical transfer of time and frequency


> 
> tvb at LeapSecond.com said:
>> Any of these methods is going to be a challenge, given their 500 ps
>> requirement and their $2k budget. 
> 
> How stable are surplus rubidium oscillators?
> 
> How close could you get if you brought two of them together, compared phase, 
> drove them to the site for a nights work, drove them back to the same 
> location and compared the phase again.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
>