Podcasting since 2005! Listen to Latest SolderSmoke

Tuesday, March 15, 2011

The Return of the Michigan Mighty Mite

Michigan Mighty Mite -- N2CQR/HI8 version

Bert, WF7I, (our correspondent at UVA Charlottesville), wrote yesterday about his past and recent adventured with a little rig that got a lot of us started in the scratch-built homebrew game: The Michigan Mighty Mite. I built one in the Dominican Republic, probably in 1993. I never worked anyone with it, but was really pleased to get the thing oscillating. I still have remnants of it (sans crystal) -- see above. Bert's e-mail and AA1TJ's recent derring-do make me want to dust off that little single FET transceiver for 3.579 MHz that I built in Italy. One QSO would make me happy. At least this minimalist stuff is keeping me away from the regens...

Here's a good article on how to build one:

Here's a site from Dave, WA5DJJ, who built a bunch of these rigs:

Bert's e-mail:

Hey Bill.

The AA1TJ postings on your blog motivated me to unearth my old Michigan Mighty Mite (the "MMM"). For me there's a lot of history, even emotion, there. I built this little rig with my friend AC7CA when we were both finishing up high school. Neither of us knew what was really going on in this circuit, other than some vague thoughts about resonance and that a transistor amplifies.

What was important to us at the time was more the fit-and-finish of the box that it was in, and making QSOs, rather than working out the theory behind the schematic. I'll email you a photo of the box as it stands now. We got a nice, blue plastic project box from Radio Shack, and figured out that those small
iPod (used to be called "Walkman")-style headphone sockets made great crystal sockets as well (they really do). I remember vividly the two of us planning out the radio, I remember trying to work with plastic (not so easy, it tended to melt and scuff up), and attaching the air-variable capacitor (not a small feat with the limited tools available). But the end product looked like a much more impressive rig than it really was. This oversized blue box with a big tuning knob, bright colored red and black banana power terminals, the cool little crystal sticking out of the top, and the Dymo-label tape proclaiming, "Rig Master" (or "blaster", or something similar -- I have to actually go see what it said!). 1/2 W of power came out of this very simple oscillator, just as advertised. But to this day, I don't know if either of us ever even made a QSO with the thing! The thrill was in the assembly of a rig from a schematic in CQ magazine, the fellowship of the two of us working on it, and seeing the thing actually WORK as promised. Time moved on, and it ended up getting shoved to a back corner of my room, and when college and work came along, it almost got totally forgotten and collected dust.

Anyway, the blog postings made me think of low-powered QRP, and I dug it out again, dusted it off, and pulled out some crystals. The thing still works just as it did 20 years ago! I was very happy to see that. I guess one of the advantages to ultra-simple, low part count rigs is that not much CAN go wrong! And if it does, it only costs a few pennies, or nothing, to fix.

The rig went on the air on Saturday night, and it was quite an interesting contrast on the work bench. On one side, my
Kenwood TS-2000, a state-of-the-art (or nearly so) DSP rig, with the "glowing numerals" and a computer interface. Next to it, the MMM, straight key and a pile of rocks! A single "super antenna" compact vertical was erected on a tripod in my backyard, with a coax coming in to the shack to a switch (functioning as a "T/R" switch, in a way). In one position, my gazillion-transistor appliance rig would function as a ridiculously sensitive and over-the-top receiver for the task at hand. In the other position, my homemade single-transistor MMM would transmit out to the vertical.

I called CQ till my hand/wrist was sore, and QSY'd between the 4 freqs I had to choose from, but to no avail. I am not deterred however. This evening, following the W4UVA club meeting, I will hook it up to our 40 m inverted vee high in the woods overlooking the nuclear reactor. It would be fitting if the possible first ever MMM QSO came from this setup.

Late Sunday night, after I had exhausted myself from "pounding brass", I was reading more from "Solder Smoke -- The Book", and found one picture that really made my day. Sitting in front of your Tandy and just to your left, was a small blurry object. Reading the caption, I saw that it was YOUR Michigan Mighty Mite! What a fitting way to end a wonderful weekend of hamming.


Bert WF7I


  1. Hehe, I can see now that it's the same rig as the image in the book.

    Thanks for posting the note. Check your email for more exciting updates from the Hoos in C'ville...


  2. I need some help on this one. Maybe you've seen the video on YouTube. So I've built it mostly close to the one offered as a kit by QRP Guys. Just because I didn't had a bigger PCV pipe and opted for a T50/2 toroid instead. With a BD139 transistor... all I got was 100mW out. I recently tried changing the coil ( version for the 40m band ) I noticed I would need a 32mm PVC pipe... and 21 turns with tap on 14 for L1 with AVG #20 - #22. All I have is 20mm PVC pipe... and #25 wire. I wonder how to calculate it properly... as I made the conversion to uH of the original design... and replicated the inductance on my coil... same for L2... and the results are still too low. I know I should get at least 400 - 500mW out but I just don't seem to get there. Thanks so much in advance. 73


Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column