Cleaning out some closets with boxes of old stuff, I ran across this Midget Monitor Radio that I got as a kid--it must've been 1957 or 1958--as a promotion for some cereal. I think it was Cheerios, but it was a General Mills cereal in any event. It's a small crystal-type radio made by the Hearever Company. I presume this was a hearing aid company from the name and the mannikin-flesh tones of the case, earpiece, and wires. I remember as a kid running around the house and yard clipping the alligator clip to various pieces of metal, sliding the brass "antenna" up and down, and actually being able to hear some radio stations, faintly, through the earpiece. The fact that there was no battery and that the device appeared simply to pluck sound out of the ether seemed like magic to an elementary school kid.
Instead of using a crystal detector, this radio uses a diode in series with the high-impedance earpiece and the antenna coil. In fact, the alligator clip is the antenna and the brass rod that looks like it might be an antenna runs a ferrite tuning slug in and out of the coil, varying the inductance, and increasing both the sensitivity and selectivity in the AM Band. It is the simplest of radios. Because there is no amplifier, it relies on the rectified power of the radio frequency carrier to drive the earphone. It is probably producing only around a few microwatts of audio, but that's enough to make the station audible in a quiet environment. It does best on strong nearby stations. For me that's KFI or KNX during the day. Both are quite listenable.
Some near relations (with a 50s rocket-ship case) of this radio are frequently seen on eBay. I doubt that DB is going to rush to junk his home theater (
http://www.telechron.net/galvanic/index.php?topic=2004.msg24434#msg24434) for this.
Images follow.
Topic: Midget Monitor Radio from the 50s (Read 2408 times)