[time-nuts] What position is measured?

[Rob Kimberley]

It's usually a manual setting of antenna delay on receivers I've used, and based on assumed delay in the particular cable & connectors. You can tweak things closer if you have a good 1PPS to compare with.

Rob K

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Pierpaolo Bernardi
Sent: 08 September 2010 11:36 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] What position is measured?

On Wed, Sep 8, 2010 at 02:16, jimlux <jimlux at earthlink.net> wrote:
> Mark J. Blair wrote:
>> On Sep 7, 2010, at 6:30 AM, jimlux wrote:

> Yes.. except that the cable's physical and electrical length *do* vary 
> with temperature, so if you're looking at the gnat's eyelash sort of 
> thing, you need to take that into account.  Maybe 10 ppm/degree, so a 
> 20 meter run will change a bit less than a millimeter.  That's down in 
> the fractional picoseconds time-wise.
>
> It's an issue if you're doing things like interferometry at higher 
> frequencies..

Would be possible for the receiver to take into account automatically the delay of the antenna cable, by measuring the delay of an echo of a signal it sends towards the antenna?  Do such receivers exists?

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