[time-nuts] Comparing PPS from 2 GPS units

Robert LaJeunesse rlajeunesse at sbcglobal.net
Thu Dec 13 18:16:27 UTC 2012

The indicated delay box is an unpowered device intended for timing composite 
video and fine-tuning for color burst phase match. As such they are analog in 
and out, require / expect defined source and load impedances (typically 75 
Ohms), are slightly lossy, and 100% passive. I suspect they are pure 
LC (ignoring the fact that all real inductors have some R as well).  I would 
expect stability in the low ns range, as more than a few degrees of color 
subcarrier shift shows up on NTSC.

Bob LaJeunesse

From: Tom Van Baak <tvb at LeapSecond.com>
To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
Sent: Thu, December 13, 2012 12:56:17 PM
Subject: Re: [time-nuts] Comparing PPS from 2 GPS units

"Lastly, there are cute little delay boxes (www.ebay.com/itm/150962422699) that 
might work. Not sure how stable they are at the ns level. But it would be fun to 
measure. If someone opens one of these please tell us if it's a coil of wire, 
some kind of LRC filter delay, or if they use those Dallas delay chips. Which is 
another solution for you -- google or eBay search for: silicon delay line.


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