tone generator
 

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?


I'm not sure what you mean by "a full oscillator." You could use a simple
buzzer or a Mallory Sonalert. The latter has a pleasant tone. I made a
mechanical oscillator out of a small speaker once by substituting a couple of
silver plated wires cut from old diodes for one of the flexible wires
connecting to the voice coil. You adjust the wires so they just make contact
normally, then wire the thing to a flashlight cell and a key, setting the
polarity so that the cone moves to open the contact. Kinda raucus(sp) but it
worked.

Doug Moore KB9TMY

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?


I'm not sure what you mean by "a full oscillator." You could use a simple
buzzer or a Mallory Sonalert. The latter has a pleasant tone. I made a
mechanical oscillator out of a small speaker once by substituting a couple of
silver plated wires cut from old diodes for one of the flexible wires
connecting to the voice coil. You adjust the wires so they just make contact
normally, then wire the thing to a flashlight cell and a key, setting the
polarity so that the cone moves to open the contact. Kinda raucus(sp) but it
worked.

Doug Moore KB9TMY

Sure, just key the speaker or power lead to see what works for your
application. ARRL handbooks have circuits.

73s,

Evan

Sure, just key the speaker or power lead to see what works for your
application. ARRL handbooks have circuits.

73s,

Evan

I am attempting to make a code key practice unit.

Greg-

The circuits using a 555 may be the easiest to build, but here is another from
back in the 60s. Some of the parts were obtained from an old transistor radio
and mounted in its plastic case, which was mounted to a piece of wood that also
held the key.

Use an audio transformer with a center-tapped primary, with its secondary
connected to a speaker. Connect the top of the primary to an audio
transistor's collector. Connect the bottom through a parallel 100K Ohm
resistor and 0.02 MicroFarad capacitor, to the transistor's base.

The key is in series with a 9 volt battery, connected between the transistor's
emitter and the transformer's center tap. A 0.2 microfarad capacitor is
connected across the transformer's primary, and a 1 microfarad capacitor is
connected between the center tap and transistor's emitter.

If an NPN transistor is used, the battery positive terminal is connected to the
center tap, and vice versa for PNP. The 1 microfarad capacitor polarity should
match.

Parts values are not critical, and you may get better results or a more
pleasing tone by experimenting.

73, Fred, K4DII

I am attempting to make a code key practice unit.

Greg-

The circuits using a 555 may be the easiest to build, but here is another from
back in the 60s. Some of the parts were obtained from an old transistor radio
and mounted in its plastic case, which was mounted to a piece of wood that also
held the key.

Use an audio transformer with a center-tapped primary, with its secondary
connected to a speaker. Connect the top of the primary to an audio
transistor's collector. Connect the bottom through a parallel 100K Ohm
resistor and 0.02 MicroFarad capacitor, to the transistor's base.

The key is in series with a 9 volt battery, connected between the transistor's
emitter and the transformer's center tap. A 0.2 microfarad capacitor is
connected across the transformer's primary, and a 1 microfarad capacitor is
connected between the center tap and transistor's emitter.

If an NPN transistor is used, the battery positive terminal is connected to the
center tap, and vice versa for PNP. The 1 microfarad capacitor polarity should
match.

Parts values are not critical, and you may get better results or a more
pleasing tone by experimenting.

73, Fred, K4DII

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?
=======
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

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?
=======
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