Michigan Mighty Mite CW Transmitter

Michigan Mighty Mite by YO6DXE
Michigan Mighty Mite by YO6DXE

Michigan Mighty Mite is a QRP CW transmitter that’s easy to built, with a rated power from 300 to 800mW as some of the people that built it stated in different articles online.

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.


1. 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 the 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

Michigan Mighty Mite Original Schematic

This was only the second transmitter I built, so I did not want to make many changes not to mess it up. 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 properly.

MICHIGAN MIGHTY MITE SCHEMATIC

To be updated soon making it much smaller and power efficient

Michigan Mighty Mite Schematic

2. 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 watt meter, tune your circuit to the highest watts output. I do that by using the 2 turns pickup coil ( L 3 ) and the LED indicator.

ORIGINAL DESIGN RECOMMENDED COIL DETAILS

L1L2
160m Band60 TurnsTapped at 208 Turns
80m Band45 TurnsTapped at 156 Turns
40m Band21 TurnsTapped at 74 Turns
30m Band15 TurnsTapped at 64 Turns

3. MICHIGAN MIGHTY MITE PCB BOARD

I may 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 down bellow. 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 for sure.

Michigan Mighty Mite PCB Board
Michigan Mighty Mite Parts Layout

4. 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.

Michigan Mighty Mite by YO6DXE
Michigan Mighty Mite CW Transmitter

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.

73 DE YO6DXE

5. MICHIGAN MIGHTY MITE – CW QRP TRANSMITTER

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