[time-nuts] Relationship of relative stability between distant locations using GPS and environmental factors

[Magnus Danielson]

From: David Andersen <dga+ at cs.cmu.edu>
Subject: Re: [time-nuts] Relationship of relative stability between distant locations using GPS and environmental factors
Date: Fri, 30 Jun 2006 15:31:11 -0400
Message-ID: <83A9C876-9680-4E6C-9FB1-B01CB1459846 at cs.cmu.edu>

David,

> Also, note that you don't really need dual-frequency for short  
> baseline synchronization.  Common-view carrier phase time transfer is  
> designed for exactly that situation.  The ionospheric problems that  
> dual frequency is designed to overcome are roughly equal when the two  
> receivers are sitting that close, so you're able to get sub- 
> nanosecond synchronization.
> 
> Environmental effects and system calibration (antenna length, etc)  
> will be your big problems.  There's been lots of good discussion  
> about heat/humidity/etc., and clocks on this list.  The usual  
> solution for the national timing labs (and tvb. :) is to stick  
> everything in a completely controlled room. :-)

Eh... well, not the antenna. :O) That you stick onto a temperature-stabilzed
concrete piller built onto the stable rock. Naturally your cable back to the
controlled room is also temperature stablizied. Don't forget the UPS with
diesel-engine which self-start and got fule for sufficient time. Also recall
that you want your controlled environment system to be on the UPS too.
Oh, and controlled environment includes humidity control, else your hydrogen
maser will change frequency with humidity.

Cheers,
Magnus