[time-nuts] Delay through GPS antenna splitter/amplifier -- an answer, and a question

Rob Kimberley rk at timing-consultants.com
Tue Mar 13 04:33:53 EDT 2007


I based my guess in the original NPL story at 1nS per foot for RG-58.....

:-)

Rob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Hal Murray
Sent: 13 March 2007 03:11
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Delay through GPS antenna splitter/amplifier -- an
answer, and a question

>>> So the cable delay should be a multiple of 317.375...ps.
>> What's the thermal coefficient of coax?
>Typically around 50-100ppm/C depending on the coax.
> High velocity cables have lower tempcos

Handwaving...

100 ft of cable is 70ns or 70000ps.
100ppm is 7ps.
10C is 70ps.

So if you start out right, you will stay close but not right-on.

I'm assuming the cable runs outside where the temperature isn't controlled.

How much of your gear has a sticker on the front telling you how many ps
between the connector and the internal terminator?


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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