Code Practice Oscillator with Tone Control

Would you like to become an amateur radio "ham"?

Many radio operators started out with a code practice oscillator with tone control like this one. The tone control is handy when you tend to become fatigued listening to the same tone all the time. You can also use the differences in tone for your own special code, in addition to the Morse Code shown on the Key.

The best way to learn the Morse Code is to find someone else who is interested in learning code. Set up a schedule and practice everyday. Make a progress chart so you can see your improvement. Take turns sending and receiving, and it won't be long until the code becomes almost like a spoken language.

The operation of the Key will become automatic, like riding a bike or driving a car. It will take hard work to get to this point, but you'll be proud when you do. If you want to practice privately (with the Earphone), disconnect the Speaker and connect the 50K Control across the primary Transformer windings, and then connect the Earphone from the center Control terminal (wiper) to one end of the Control.

With these connections the Control will act as a volume control as well as a tone control. You may replace the 50K Control with a fixed resistance if you want a fixed tone and volume. The tone from the oscillator is not designed to be a pure sine wave, because it has been learned that a pure sine wave signal is more tiring than a tone full of harmonics.

The theory of this oscillator is given in other projects, so we won't repeat it here see oscillator section.

However, we will discuss how the tone control works. When the 50K Control is adjusted for less resistance in the circuit, less resistance is present across the 0.05uF Capacitor so that it charges faster between pulses. This causes the pulses to be closer together and therefore the frequency (and tone) is higher.

The opposite condition occurs when the Control is adjusted for more resistance. If you become proficient at Morse Code, the next step is to contact your nearest Radio Shack store and see what study materials are available for the written part of the FCC exam. Good luck!







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