[time-nuts] What position is measured?
lists at rtty.us
Wed Sep 8 11:35:04 UTC 2010
Setups like that do exist and are fairly common. I have never seen the
technique integrated into a GPS receiver. It's normally done with a
secondary setup. My observation is that something like 99% of the GPSDO's
out there never get their antenna delay set to the proper number. It's
commonly done for surveying work, but not so much for timing. The cell phone
guys can get away without that fine an adjustment, so they ignore it.
From: "Pierpaolo Bernardi" <olopierpa at gmail.com>
Sent: Wednesday, September 08, 2010 6:35 AM
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
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
>> temperature, so if you're looking at the gnat's eyelash sort of thing,
>> need to take that into account. Maybe 10 ppm/degree, so a 20 meter run
>> 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
> 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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