The Cranky Sysadmin A world of technology, fun, and ignorant rants.

December 16, 2011

Before I Build a Tranceiver…

Filed under: ham radio — Cranky Sysadmin @ 9:18 pm

I picked up a copy of the ARRL Handbook for Radio Communications. I bought and fixed a nice Fluke 1935A frequency counter, and I just built an LC meter from mostly parts at radio shack.

An LC meter allows you to measure the value of capacitors and inductors. I want something like that so I can wind my own inductors and have an idea what their value is without doing a lot of math (f=1/(2*pi*(sqrt LC))). Kerry Wong has a nice page describing a reasonably accurate LC meter built around an ATMega328P and a LM339 comparator. I built mine based on that.

I made a few changes to accommodate the hardware that I have. First and easiest, I used a 110uh coil and changed the constant for the coil in his program. Second, I used a Parallax LCD (Arduino library here) which required that I make more changes. I ignored the frequency counter portion since I have a nice counter already. I’m using an Arduino Mega2560, which doesn’t grant access to timer1, so I had to go into the frequency counter library and adjust. It was a fairly uninvasive change. I’ll have to remember to send a diff to the author and post the modified library. My next step with the meter is to get it off the protoshield and into a nice project box. Here is a picture of the ugly rat’s nest as it is now.

2 Comments »

  1. Will you be publishing the schematic & source code of this project?

    Comment by Indy — January 14, 2012 @ 5:55 am

  2. Thanks for reminding me. I’ve been so involved in other aspects of my new hobby that I forgot to publish the diffs. I’ll get right on that… soon.

    Comment by Cranky Sysadmin — January 14, 2012 @ 8:35 am

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