Back in the very early 1970s, Radio Shack sold a very useful, inexpensive signal injector. It was cylindrical, and I believe it was powered by either one or two "c" batteries. At the front was a probe and either the back or side had a momentary push button to activate it. It was basically shaped like a flashlight with a probe sticking out of it. It produced a harmonic-rich square wave that was great for injecting a test signal into audio circuits as well as IF and HF RF circuits.
There are times these days when such a handy, portable device would be useful in my electronic toolbox.
Does anyone know where I can obtain one of these? A search on eBay and the internet has not proved successful.
It isn't finished, but here is the scan of the original instructions, a homebrew that someone made, and the schematic.
http://www.antiqueradios.com/forums/viewtopic.php?t=109446&highlight=Simple device, you could probably pen tube it (My son's school has some MONSTER pens that are about 3/4 inch across, would be GREAT for HV probes and other such thing. Waiting for the ink to dry up, and I get them BOTH!!! ).
Hope that helps. I'm going to build one as well.. You're right, they are about indespensable. That, and a signal tracer is a poor mans sig gen and scope!
--Shane
