The Impoverished Radio Experimenter #2
"Tricks,
tips and secrets to help the builder of simple radios and electrical gear
achieve high performance at minimal cost!"
Building radios (and transmitters and antenna-tuners if you have a ham radio license) it about matching the proper capacitors with the proper coils to get a desired frequency. You can wind a coil and hook it up to a capacitor, but how will you know if it's right? A grid-dip oscillator, or gdo, is a measurement device that will tell you. And it's very simple - first used in the 1920's.
Here,
you learn to build a one-transistor model around the components you can salvage,
steal or buy. It's a great exercise in building in itself. It forces you to
solve the mechanical problems of building that are often more difficult than
the electrical. And when you're done you have a machine that makes coil winding,
and tank circuit fabrication predictable rather than merely guess work. You
won't need to have the exact coil form specified in that old magazine article.
And you can figure out for yourself how many turns to use.
You get instructions on gdo use reprinted from the manual supplied
with the classic Millen gdo fifty years ago. You get photos of ads and specs
so that if you want to buy a used gdo, and they're out there, you'll know
what exists. 
You
could even convert an old tube model to solid state.
You'll learn to use the gdo along with simple formulas that will put your tank circuits on the frequencies you want. You can use other formulas along with a known coil or capacitor to measure the value of an unknown coil or capacitor. In other words, for a radio builder, you gotta have a volt-ohmmeter and gdo. Otherwise, you're just wasting valuable time.
You'll
learn how to take a pentagrid converter tube and build a one-tube shortwave
converter that will put shortwave broadcast stations on a frequency that an
ordinary AM radio, or crystal set for that matter, can receive. While your
crystal set buddies are listening to some talk show idiot on the AM band,
you can be listening another equally ridiculous talk show idiot on 5 or 10
mHz! And you can listen to the respectable BBC out of London, or stations
in Canada, Germany, Belgium, China, Cuba (talk about BS!) and elsewhere. It's
powered with the simple power supply built in Experimenter Volume One.
You'll learn how to make a top rate slow-motion dial drive for
your radio. Its 7.5 to 1 ratio makes tuning 
stations
easy. You'll find that it works far better than many expensive antique dial
drives. It's easy.
You'll learn how to make a simple rig for winding professional quality hi-Q space wound coils. It's easy and low-cost.
You get many more hints, tips, and ideas for exploration. Some people prefer to whine that they can't find parts. It can be a problem, but geez... in the time it takes to whine, you can build your own parts.
Valuable info. Cheap! Get a copy. 5-1/2 x 8-1/2 booklet 48 pages
No. 22571 ... $5.95
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