Michigan Mighty Mite is a QRPP CW transmitter that’s easy to built, with a rated power from 200mW to 800mW.
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With this particular built, I only got 200mW at first, from a plastic case 2N2222 transistor. I will experiment with more transistors though, hoping to get at least 300mW output power. It seems that the first version I built was not that different… but I do suspect that the BD139 transistor I used in the first version was nothing but a low quality part far away from the proper characteristics of a BD139.
THE ORIGINAL SCHEMATIC
I discovered the schematic of the Michigan Mighty Mite on the SolderSmoke Blog, as I like to read their articles quite often. I found a lot of the projects from my “to do list” built by other people in their blog articles. And not once, the articles helped me fix some of the issues I had and made things work properly. With that in mind, here you have the original schematic of the Michigan Mighty Mite transmitter. You can build it for most of the HF bands, but I noticed it performs better on the 80m band. What I love the most, is the really nice tone it has. It sounds a lot like an old tube CW transmitters, a pleasant tone to my ears.
The original schematic is credited to two hams: Ed Knoll, W3FQJ and Tom Jurgens, KY8I.
MICHIGAN MIGHTY MITE ORIGINAL SCHEMATIC
This was only the third transmitter I built, so I did not want to make many changes. All I did in my particular version, was to place a bandpass filter on the output. I also placed a power ON LED indicator, and another LED to light up when it transmits. This one also helps me tune the transmitter. The MMM+ 40m that I built as my second CW transmitter didn’t performed so well when it comes to the output power. For that reason I wanted to build one as close as possible to the original and see if there is a difference. Turns out there is none, but I’m happy I tried anyway. The Michigan Mighty Mite is fun to build, but it seems complicated compared to the Ten Minutes Transmitter, the very first CW transmitter I built.
MICHIGAN MIGHTY MITE SCHEMATIC
To Be Updated Soon Making It Smaller And Power Efficient
THE COIL AND SCHEMATIC DESCRIPTION
This little circuit can put out about 500mW RF on 160, 80, 40 or 30 meter amateur radio bands. The core of the design is a crystal controlled oscillator, which is fed into an RF output transformer. After you build the circuit, check if the transmitter works using a radio tuned on the frequency of the crystal. If everything went well, you should hear the tone. You will need to tune up the circuit with the variable capacitor, so if you don’t hear a tone, slowly turn your variable capacitor until you hear one. If you have an RF wattmeter, tune your circuit to the highest output power. I do that by using the 2 turns pickup coil ( L 3 ) and the LED indicator.
| BAND | L1 | L2 |
|---|---|---|
|
160m |
60 Turns Tapped at 20 |
8 Turns |
|
80m |
45 Turns Tapped at 15 |
6 Turns |
|
40m |
21 Turns Tapped at 7 |
4 Turns |
|
30m |
15 Turns Tapped at 6 |
4 Turns |
MICHIGAN MIGHTY MITE PCB BOARD
I will re-design the PCB board at some point, but for now this is the one I used when building the Michigan Mighty Mite transmitter presented in the video above. I designed everything in a rush, but I already have some ideas to improve it a little and make it easier to build. But this, sometime in the future.
BUILDING THE CW TRANSMITTER
I had no equipment to measure the low pass filter or the coil that I made for the Michigan Mighty Mite. For sure they are not perfectly adjusted. I’m also suspecting that maybe that’s why the power output it’s not as big as others managed to get. Lately I did purchased some more equipment to do measurements and adjustments, so I will try to do that and see if I can squeeze a little more “juice” out of it.
It was a lot of fun building and experimenting with this simple CW transmitter, so I hope you will also enjoy it. In my case, I did learned a little bit about how a simple transmitter works, so it was worth building it. I will repeat myself one more time, but I really loved it’s tone. It has a specific tone and I really like how it sounds.
MMM+ 40m CW TRANSMITTER
I wanted the Michigan Mighty Mite to be my first transmitter project, but I did not had the parts I needed to complete it at that time. For that reason I decided to build the Ten Minutes Transmitter instead. This particular design of the Michigan Mighty Mite was the second CW transmitter I built, inspired by the MMM+ 40m kit from QRPGuys.
73 DE YO6DXE