I’ve been listening to some of the older episodes of the soldersmoke podcast, and figured I’d put together one of the michigan mighty mite transmitters that they’ve mentioned so often. I even had a 3.579 colorburst crystal in the junk box.
The michigan mighty mite is a very simple 7 component transmitter that is easy to build. It is a great first project for someone getting into homebrewing.
The schematics and more detailed instructions can be found here.
Here is my version.
I wound the coil on a pill bottle and used a polyvaricon from an old am radio. It is using a 2n2222 transistor and a 3.579 crystal. The switch is used as the key.
As you can see in the following wave form, this little transmitter really needs a filter before using it on the air. The scope’s frequency counter is even reading the second harmonic of 7.15MHz instead of 3.579MHz.
Looking at the FFT, you can clearly see the harmonics in the signal.
If you build this transmitter, make sure to add a low pass filter before attempting to use it on the air.