Output

goes low. QI base voltage returns to 6 volts and the whole thing starts again. Eureka—an oscillator!

Figure 2. A 500k Q volume control with a switch can replace Si and R3.

The transistors are not critical. PNP and NPN types with HTs of between 200 MHz and L.t GHz, plastic low power, metal signal, RF power output, and even a couple of unmarked ICKTs were tried, and all worked fine with very little difference in the frequency,

Iwo components do affect the frequency. Make R3 smaller and frequency goes up. Make C2 larger and it goes down.

Voltage is another non-critical. Varying the supply voltage from 4,5 to 15 volts changed the frequency somewhat but oscillator start-up occured every time power was switched off and on.

If money is no object, make this thing variable by changing the value of R3 to 68kO and adding a 5Q0kO potentiometer in series.

As mentioned before, the output has a definite lack of purity.* The waveform is actually a spike with a repetition rate of about a thousand hertz - If the experimenter views the output on an oscilloscope he will see all kinds of fuzz and garbage along with the original one kilohertz pulse.

Uses in the bygone days of ham radio when the experimenter used to fix his own stuff instead of shipping it back to the importer, one of the more indispensable pieces of test gear was the signal injector. Starting at the speaker in a receiver or audio amplifier and working backward along the signal path with the injector, [he defective stage was found when ihe signal disappeared.

All of that garbage from the oscillator actually has some usc\ While checking ihe audio stages* the 1000 Hz comes through. Once into ihe IF and RF sections the fuzz shows its true stuff. The oscillator has usable output out beyond 30 MHz

I run a burglar alarm business. One of the things that makes the alarms ring in the night is the four-w ire cable that runs from each of the many sensors to the alarm panel. Things go fme until a couple dozen of these come through a hole in the back of the panel and the ID tags have fallen off half of them. What to do? Connect the output of the oscillator to two of ihe four wires in one of the Lines at the far end of the run. Back at the panel I check out the unknowns by listening to each in turn with a small battery powered audio amp.

Hou about a code practice oscillator? Simply connect a ke\ in sencs between the output capacitor C3 and an audio amp and pound away.

Simple test equipment-simple to build, simple to get working and simple to use with all kinds of uses. Thats the best kindlRJ

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