Sunday, July 22, 2012

Rainy afternoon project with the kids: Coax Tester!

After finishing up the souncard interface yesterday, I thought that I would be done for a few days, but a house full of boisterous kids on a rainy day dictated otherwise.  As they say, necessity is the mother of invention, or in this case, maintaining my sanity was...  ;-)

I recalled watching a YouTube video by W5CYF (Tinker John) on how to make a simple go/go-go coax tester.  It seemed like a good project for the kids and I to do.  Like John, I used a green LED to mean the coax is bad, but hey, it's what I had on hand.

This is a simple, quick and dirty schematic of what we built:

In a project list this, there are a few things that kids can do, and a few that an adult needs to do.  While watching the kids play with the drill or soldering iron would be entertaining in a scary sort of way, the trip to the hospital afterwards would have been annoying.  However, seven year olds are good at sorting resistors by color, and 9 year olds are good at tightening screws.  They are also both helpful when small parts are dropped by fumble fingered parents.  Just remember that kids are kids, and tend to be distracted and not remember the goal.  They also like to fidget A LOT.  My son got to spend a few minutes in his room due to this, but he settled down and was back for the finish and testing.

My Parts List:

  • 1 x SO-239 connector
  • 1 x 9V battery connector
  • 1 x 350 Ohm resistor
  • 1 x Green LED
  • 1 x Small project box
  • 1 x 7 year old boy
  • 1 x 9 year old girl

Time to Completion:
  • About two hours, after all, the kids were helping me!  ;-)

Here are a few pics:

Here are the two proud builders!

Picture of the tester.

In this picture, I used a small bit of solder to simulate a piece of bad shorted coax.  Notice the green LED is on.  Green usually means good, but in this case, green is NO-GO!

Again, this was a fun little project that will give you an absolute basic go/no-go test of a piece of unknown coax.  It won't tell you impedance or length, if you need those tests go get an MFJ-259B or something similar.  If you want to make sure that you don't have a dead short and won't blow up your finals, this is the tool for you.  ;-)


Richard, KK4JDO

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