Simple Coax Testing
by
HS0ZHM - Greg Lee

In some of the many different antenna project articles you have seen, folks mentioned "testing" the coax before it is installed (or after you discover a problem after the installation), but I didn't find any step by step for newbies that were starting off with little or no knowledge in electronics and radio like me.  So I started documenting my own learning about testing coax, knowing that if I don't do this very often, it will be like income taxes, and the next time I go to do it, I would sort of remember doing it but not exactly how I did it.

It started when I was trying to fuddle my way through learning to use an SWR meter to check out my VHF antennas (the 450 ohm Slim Jim ladderline antenna project from your site, as a matter of fact) and in adjusting the SWR I had to go beyond the suggested points for the feedline.  Being new to all of this I was wavering in my confidence level and started to wonder why the measured spacings according to the instructions taken from a particular antenna project for the feed points was so way out.  (Although realizing each antenna project is a bit unique due to the different operating environments and other factors, I thought the project "recipe" would be fairly close.)

My training in Geography is all about getting the big picture (total systems overview), and the logic of all that set in when I was checking one antenna.
 
That's when I started to mentally sketch out the total system....of which the antenna was one part, but all the stuff between the radio and the antenna were also part of the "antenna system"....and by testing SWR of the antenna (which is what I thought I was doing) I was really testing the SWR of all the things from the radio (signal source) to and including the coax, connectors and the antenna.  In my focusing on the antenna, I was assuming the coax and all connectors between the radio and the antenna were OK, but in fact, I hadn't really tested them.  I remembered checking the continuity of the PL259s that I installed, but I never really separately tested the entire coax with a dummy load or with an ohm meter for the correctness and proper continuity!

As you are well aware, ham radio is such an integrated system of bits and pieces all requiring some (and most times more) knowledge than newbies have readily at hand. 

In trying to deal with some of these questions, I compiled an illustrated paper on simple tests for coax.

So how do you test a length of coax with the connectors installed so you can add it to the antenna system to be absolutely sure everything is OK and nothing was installed improperly? That is the question, hopefully this article will answer for you!

The complete instructions on how to test coax after the connectors are installed can be found in the document download below available in PDF form.

You will need Adobe reader....download the article here. (590KB)

This article provided courtesy of Gregory (Greg) Lee, HS0ZHM
Rural Training Center-Thailand http://www.neighborhoodlink.com/Rural_Training_Center-Thailand

See this link that is loaded with Emergency Preparedness information:   http://www.neighborhoodlink.com/RTC-TH_Tech/pages

Email Greg at:

RTC2K5 AT gmail.com
hs0zhm AT gmail.com