[time-nuts] Cable delay correction for Tbolt Cs substitude

Tom Van Baak tvb at LeapSecond.com
Sun Oct 16 21:24:50 EDT 2011


Mark, Warren,

That's correct. Some dual-frequency geodetic-grade GPS
receivers use thermally stabilized antennas. It's one more
trick in the quest for nanosecond stability and there's no
reason one couldn't homebrew one. There are photos of
them on the web.

It would also not be hard to test, especially if you use a TEC
so you can manually set the temperature way up and down
over fractions to multiples of an hour. Or compare it in real
time against an unstabilized sister antenna and TBolt.

Good reading, performance charts & graphs:
  http://www.ngs.noaa.gov/CORS/Articles/metrologia-2.pdf
  Geodetic techniques for time and frequency comparisons
  using GPS phase and code measurements

More info at CORS and IGS sites:
  http://www.ngs.noaa.gov/CORS/
  http://igscb.jpl.nasa.gov/

I agree on your cable comments. I used Andrew Heliax on
my L1/L2 antenna back when I was running a Z-12T. At its
best it was good to cm levels, way below 1 ns.
  http://leapsecond.com/pages/quake/panga-tvb1.gif

Would it be possible to run a controlled current down the
coax to maintain constant temperature 24x7? You could
use its resistance as a proxy for temperature.

/tvb

----- Original Message ----- 
From: "Mark Sims" <holrum at hotmail.com>
To: <time-nuts at febo.com>
Sent: Sunday, October 16, 2011 5:28 PM
Subject: [time-nuts] Cable delay correction for Tbolt Cs substitude


>
> Yes,  at one time there was some very precision surveying antennas that were temperature controlled.   I'm not sure if 
> they were just controlling just the preamp or the whole antenna,  but I got the impression that they were controlling 
> the temperature everything inside the "radome" package.
>
> At one time I did some TDR measurements on a piece of coax (I think it was 100 feet of black RG59).   The day/night 
> prop time variation was under a nanosecond.   Something tells me that the cable delay changes itself won't make any 
> difference.
> -----------------------------
>
> Does anyone ever add a temperature controller on the antenna? Maybe that
> should be my next test.






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