(Bent Technology Network)
What is ''BTN''?
There is now a VERSION 2.0 of this thing! Scroll down to see it. :)
|WHAT IS THIS?? (V1.0)|
Don't believe me? Well, there are some actual O'scope images, below! What is it??? It is the x-tal transducer "beeper" from a digital wristwatch! Yes, indeed, it DOES oscillate, as long as you can isolate a portion of the x-tal to give you feedback to the base. A dremel tool with an engraving tip will work, as will very careful use of a soldering iron. You simply need to etch a straight line across about 1/4'th of the circular area of metal plating, so you end up with two electrically isolated sections. The 25% section feeds the base, the 75% section feeds the collector. The watch back, itself, is gnd.
If you fed the DC into the 1K resistor (instead of connecting to an antenna) the x-tal would oscillate anywhere between about 5-15Khz. (I later measured the frequency, it was close to 8Khz.) Yes, it is quite shrill! By using a small choke (about 50uh) to feed the collector, it wants to oscillate at RF. This particular x-tal runs at about 548 Khz, low on the AM B'cast band. A standard AM radio picks up the signal loud and clear up to several feet away. AMAZING... and I could hardly believe it myself! This is why I am documenting this insanity here on the WWW! Nobody would believe it if it wasn't absolutely true! :) (You can't make this stuff up - truth is stranger than fiction! Here's living proof!)
This is, without a doubt ***INSANE*** BTN!!! Who would have EVER even CONCEIVED of such a thing? Well, that is part of the fun of BTN! Doing something totally off-the-wall like THIS! Using something in ways the engineers NEVER intended or even imagined. Ya just gotta LOVE it!!
I've done a little more tinkering. By changing the coil and putting a variable capacitor across it, I am now able to tune this thing through a number of distinct resonances. It is very stable at each one, and can be adjusted a few hundred Hz each way from each center. Since it was rather late, I haven't had time to fully document things. I just wanted to get this page online, so others could see what applying a little BTN can accomplish! ;)
Because these x-tals were NEVER MEANT to operate like this, they are unpredictable. Plus the fact that you will be etching the conductive surface into two seperate parts is another wild variable! You may end up with a unit that fails to oscillate at all. Don't give up... find another dead watch, and try again! ;)
The antenna should be a few feet of wire. To connect to something larger could stop the oscillation. You can experiment by putting a 1K or 470 ohm R in series with a longer wire. The range is quite short, naturally, but the audio can be VERY GOOD! (Mine was!)
|Actual O'Scope trace! (V1.0)|
|Another O'scope trace (V1.0)|
BTW, I will be doing a few more experiments, so check back again. Last update: 03/03/2008, @ 9:00PM EST
I have been busy with other, much more practical & useful projects. This one is pretty much on the shelf, now. It was fun, that's for sure! (I may tinker with it again in the future. Who knows?) Meanwhile, please, continue browsing the rest of the site! :)
I do have plans to actually put something like this on the air, if at all possible! If I can get another dead watch transducer to generate a signal on or near 3880, I will feed it through the B.O.B. JR transmitter and see if it is enough for anyone to hear me. :) Theoretically, I SHOULD be able to get at LEAST a watt or two! :)
|BTN AM tx V2.0|
|O'scope trace, V2.0, sinewave|
Here's a scope trace with music playing through it:
|O'scope trace, V2.0, music|