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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:
http://www.qsl.net/wb5ude/kc6wdk/transmitter.html

Here's a site from Dave, WA5DJJ, who built a bunch of these rigs:
http://www.zianet.com/dhassall/Michmitymite.html

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.


72/73,

Bert WF7I

Monday, March 14, 2011

Happy Pi Day! (3.14 Get it?)

http://www.collegehumor.com/video:1948828

One of the many benefits of having a kid in elementary school is that you are made aware of important days that otherwise might escape your attention. Like today: International Pi Day. While the mathematical connections might be a bit flaky, I liked the above video.
Slashdot put it this way:
I'm not saying it's as good as Lady Gaga or Justin Bieber or something, but it's a great way to get ready for Pi day which is tragically still not a federal holiday. Write your congressman.

Sunday, March 13, 2011

Podcast QRM Culprit Found: WBIG-FM 100.3 MHz

Listeners noticed that recent SolderSmoke podcasts had some other audio playing faintly in the background. At first I though this must have been AM broadcast band breakthrough, so I built a little crystal radio, only to discover that the powerful AM stations here were not playing the ZZ-Top style classic rock that I was hearing in background noise. Bert, WF7I, suggested that I listen carefully to the QRM for a call sign. I tried that this morning. I couldn't get a clear call sign, but I picked up the unmistakable rhythm of Peter Frampton's "Do You Feel Like We Do?" Fortunately that song is 1) infrequently played and 2) quite long; I had enough time to take a spin around the FM radio dial. Sure enough, I caught the tail end of the Frampton song on WBIG-FM 100.3 A quick check of the web shows that this is a 50,000 watt station that has its transmitter within about 1 kilometer of my house. Bingo.
The mic cord is just about 1/2 wavelength. That would put the high voltage nodes at the ends, right? I notice that the interference drops noticeably if I wind up the cord, and increases a lot if I stretch out the cord.
I can hear some other stations in there also (one country station). It may be that there are multiple FM stations broadcasting from that antenna site. I can see the tower's red lights blinking from my front lawn.
Thank you Peter Frampton!

Regen Madness



How many times have I said "never again, no more regens"? I guess I need a twelve step program or something like that. This latest bout of regen fever started with the King's Speech movie. So I blame the Brits. All of them. Then this Belgian guy with the video comes along (see above). Now I find myself drawing out a schematic for the old regen that I picked up years ago at the Kemption Park rally in London. Someone please, STOP ME!

Job Opportunity: MAKE needs THE KNACK

Sounds like the folks at MAKE are looking for someone with THE KNACK. Check it out:
http://blog.makezine.com/archive/2011/03/awesome-opportunity-to-work-with-make.html

Saturday, March 12, 2011

HomeBREW (literally!) Your Own Microphone!



During those dark days in which I was using my Astatic D-104 mic for podcast purposes (not a popular move) I checked on the mic element inside my chrome lollipop and found it to be the original crystal "Rochelle salt" element. I remember wondering about the Rochelle salt: What the heck was that? Well, this morning, the hippie technologists over at the Make blog explained it all to me via the above embedded video. It turns out that you can MAKE piezoelectric Rochelle salt crystals in your kitchen using -- get this -- soda ash, coffee filters, and -- wait for it: CREAM OF TARTAR sauce! I'm not making this up.

Thursday, March 10, 2011

The Hobbit Hole

In the interest of preserving what I suspect will become an important piece of amateur radio history, I'm posting some pictures of the underground radio shack and workshop of Michael, AA1TJ.

Michael describes the facility this way: The shack is under two feet of snow at the moment, but from the surface it looks for the most part like any New England spring-box cover that you come across while walking in the woods. Only, when you lift this cover you discover Dr. Evil's secret underground radio laboratory, a re-creation of Hogan's Heros radio station, or what I affectionately refer to as the "Hobbit Hole."

The two of us burrowed down 13 feet, breaking up boulders the size of a VW Bug as we went. Aside from the pick and shovel work, I used both one and two-handed sledges along with an assortment of rock chisels and pry bars. Everything came up in 5 gallons buckets.

The lower-level slab used hand mixed concrete. The walls are 12" thick insulated masonry blocks; a Canadian-made product called, Sparfill, that's unfortunately no longer available here. We called in Ready-Mix for the concrete roof. The interior dimensions are a luxurious 2m square.

As luck would have it, I had just taken some photos of the interior for my pal, DL3PB. Please find them attached. Actually, in one bench corner you'll see the 2,400RPM AC induction motor and 400 pole stepper motor that I plan to use in the "Full Monty" version of the present project.


Mike has a wonderful posting on his blog today: http://aa1tj.blogspot.com

Wednesday, March 9, 2011

Shuttle and Space Station (and Sunspot)

Check it out! The ISS and the Shuttle Discovery captured by an amateur astro-photographer as they passed in front of the sun, with major sunspots nearby! Catalin Fus of Krakow, Poland, had his solar-filtered telescope trained on sunspot 1166 on March 7 and recorded this amazing conjunction. Thanks Catlin and thanks to spaceweather.com.

I had the whole family out in the front yard after dinner last night. ISS and the Shuttle made spectacular pass over the Washington DC area. We saw both rise up from the Northwest and then blink out after passing overhead. The shuttle (I think) was about one minute behind ISS.

40 years of Spice

Bob, W8SX, sent me an interesting article from EDN on the recent commemoration of the 40th anniversary of our beloved SPICE program. Check it out:
http://www.edn.com/blog/IC_Design_Corner/40584-SPICE_a_40_year_old_open_source_success_story.php

Tuesday, March 8, 2011

Watch the Shuttle fly with the Space Station


The two spacecraft are un-docked but orbiting close together. There is a good visible pass over Canada and the U.S. this evening (see above -- all times EST). Go to http://spaceweather.com/flybys/ to get the times for your location. Hurry, I think the Shuttle comes home tomorrow.

AA1TJ's Dream: No Tubes, No Transistors... ALTERNATORS!

Treat yourself today to an experience in radio enthusiasm and innovation: Go to AA1TJ's blog and read about his latest creation: The Schmidtschem. Michael begins his post this way:

I've dreamed and schemed, off and on, for the last twenty five years over the prospect of constructing a complete, high-frequency (HF) amateur radio station without the use of vacuum tubes or semiconductors... Having considered and subsequently rejected a number of esoteric possibilities, I eventually concluded that a system based on electromagnetic alternators was the most promising.

He has a prototype on the air, using it with a no-gain receiver, and he is making a lot of contacts. Check it out: http://aa1tj.blogspot.com/

Sunday, March 6, 2011

Crystal Radio Sleuthing

As part of my effort to stamp out broadcast interference to the SolderSmoke podcast, this weekend I reassembled the crystal radio that Billy and I had built in London. It is REAL simple: Just a parallel LC circuit with a germanium diode detector and some high impedance phones. (I also put a chunk of galena and a cat's whisker on the board -- that's for when I get the urge to form my own PN junctions.) As expected, I immediately heard two AM broadcast stations: WFAX 5 kw 1220 kHz (religious) and WUST 20 kw 1120 kHz AM (mostly foreign language). I found out the hard way that these stations reduce power at night: I was bragging to my wife about the EXCELLENT reception I'd been getting on the crystal set, but when, after dinner, I brought her into the shack for a demonstration, she could barely hear anything. Oh well...

But here's a surprise: These are NOT the stations that are getting into the podcast! With the crystal radio in operation, I did some audacity recording and then quickly checked to see if the breakthrough sounded like what they were playing on WFAX and WUST. NO! The breakthrough was ZZ Top! I'm guessing that the breakthrough was from an FM broadcaster. I note that the length of the cord to the microphone would seems like it would be a nice antenna for the FM broadcast band... What do you guys think?

Whatever the source, I think I have taken care of the problem. I got big ferrite toroid core and wrapped about ten turns of the mic cable through it. No more broadcast breakthrough.
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column