This is an instructable on how to make a small, portable morse code practice keyer that you can put in your pocket, take anywhere and practice learning Morse Code. It is composed of only two components and takes about half an hour or less to make.
I have taken a keychain tone generator, used for tuning musical stringed instruments, and simply added a contact switch between the tone generator circuit and it's speaker. Very cheap, portable and useful for learning Morse Code.
Watch the video to see how it works.
Step 1: Open tuner case and solder in wire to speaker
Your tuner probably won't look like mine but the keychain tuners are all similar.
Open the case.
Unsolder one of the wires leading from the oscillator circuit to the speaker.
Route that wire outside the case through a small hole you have to file or drill in the side of the case.
Solder another short piece of wire to the speaker terminal that you just unsoldered. Lead that wire outside the case also.
Step 2: Mount contact roller switch to case
Drill the holes and bolt on the switch and screw the speaker cover back on to the tuner.
Note, you can use any kind of contact switch but this one most simulates a real Morse Code key. You could even mount a miniature push button switch to the case and make the practice keyer even smaller - personally I like the feedback the roller switch gives.
Then solder the two wire leads to the switch.
Screw the battery cover back on.
Practice Morse Code diligently.