I am attempting to make a code key practice unit. I cannot find
anything out there! I am going to make a simple tone generator so I
can practice. Is this feasible? Are there any other designs out
there besides making a full oscillator?
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A good but simple code key practice oscillator is a single transistor
'double T oscillator' which can be found in the ARRL Handbook .
I built mine from the circuit published in the 1995 Handbook , page 26.19
It produces a 'clean' approx 750 Hz output.
I added a LM386 audio power IC to drive a small loudspeaker.
The complete circuit was built 'ugly construction' and powered by a 9V
battery.
The external Morse key serves also as the power switch.

Many moons ago I built a code practice oscillator using a 555 timer IC ,but
the tone sounded rather rough ,the output NOT being a sine wave.

Frank GM0CSZ / KN6WH