So far we've sent out 9 of these color burst 3.579 MHz crystals. It occurred to me that I should make sure these particular rocks work with the Michigan Mighty Mite design we've been advocating. So today -- still in something of a turkey-induced haze -- I pulled out the surviving remnants of the MMM that I built back in 1993. That one had been for 40, so I rewound the coil for 80 using the data from this MMM site: http://www.qsl.net/wb5ude/kc6wdk/transmitter.html
I was hoping that this rig might oscillate even without the variable capacitor, but mine did not. Once the cap was placed in the circuit, the oscillations began. It sounds pretty good on my Drake 2B.
I have not yet wound the secondary (antenna) coil but (as I suspected) the oscillator works fine without it.
So, no excuses folks. These cheap junk box crystals work. Time to build one of these things and join the ranks of hams who have homebrewed a transmitter (and, of course, The ColorBurst Liberation Army).
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Bill, you have recruited another CLA soldier! I collected no less than 7 old TV sets yesterday and will soon be scrounging parts and liberating crystals for a few MMMs. Thanks for the inspiration! 72, de KT5H, Steve
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ReplyDeleteI've been looking at all the MMM references, and I'm left feeling a little short. There is no explicit mention of the relationship between the tap on the coil, and the other ends. Right now, seeing as how this is a Pierce oscillator, I'm guessing the tap is closer to the collector of the transistor, reducing the amount of energy feeding the crystal, but it's not explicit. Y'all are to be congratulated, making it work without all the details!
ReplyDelete73,
Steve
W1KF