The QRPGuys K7QO Code Practice Oscillator (CPO) is about as simple a kit as you can get. The parts list includes 11 components, and four of those are stick-on rubber feet! As you can see from the photo at right, it’s really just a battery (a CR2032 coin cell, not included), a phone jack for the key, and piezoelectric oscillator.
All told, there are only 14 solder joints to make, and about the only thing you can get wrong is to put the oscillator in backwards. That, plus the fact that it only costs $10, makes this a great starter kit.
The piezo oscillator is really loud, but you can add a volume control, if you like. Instead of soldering in a jumper between two pins, you add a 50-ohm potentiometer. What I did was to simply cover up a portion of the output port of the oscillator. That seemed to work pretty well.
I’m thinking that building this kit might be our next ham radio activity down at the Ann Arbor District Library’s Secret Lab.
Jonathan says
Very cool. I built the Pacific Antenna (QRP Kits) CPO this weekend. It was my first soldering project and kit build ever. It felt so great to put something together that I immediately ordered another little radio kit upon completion. I hope that you’re able to share the joy of building with others at the Secret Lab!
Jonathan
KC9WIZ
Dan KB6NU says
That looks like an interesing project, too. I like that it has a built-in key.