[time-nuts] Safely getting the electrical length of a connected antenna feedline

Bob Stewart bob at evoria.net
Thu Aug 11 14:56:09 EDT 2016


Why is velocity factor an issue?  Aren't we only interested in the electrical time from one end of the coax to the other?
Bob
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      From: Didier Juges <shalimr9 at gmail.com>
 To: Bob Albert <bob91343 at yahoo.com>; Discussion of precise time and frequency measurement <time-nuts at febo.com> 
 Sent: Thursday, August 11, 2016 1:20 PM
 Subject: Re: [time-nuts] Safely getting the electrical length of a connected antenna feedline
   
I used the PPS from a Thunderbolt (fast rise lime, low rep frequency, was handy) and a digital storage scope and a couple of resistors to make a reflectometer based on this experiment:

www.ko4bb.com/getsimple/index.php?I'd=coax-cable-impedance-matching

You can very clearly see a 50 ohm/75 ohm mismatch.

The biggest variable will be the velocity factor.

Didier KO4BB

  


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