"How to Become a Radio Amateur," ARRL 1968. This two-transistor code oscillator can also be "recycled" as a built-in sidetone monitor for "A Simple Two-Tube Transmitter" from the same book, which I am about to build.
The oscillator is built on a single terminal strip mounted on a piece of scrap wood. Back in the day, the parts cost "about $3.50" which is very expensive in modern terms, now that you can get a gazillion transistors and other components onto a single IC.
As usual the ARRL's instructions for the beginner are very thorough. In the schematic, note C3, the 0.01 uF capacitor in the headphone output circuit. I will be mentioning it again later in the photo gallery.
Very easy to round up these parts from my vintage junkbox, apart from the transistors. Of course I could have used just about any modern day transistors from Radio Shack but I couldn't resist the temptation to use the original specified part, which I found at a specialist online store in California. I also used vintage Ohmite resistors (from my "Little Devils" drawer set), mainly because they had longer leads. (Those two new 10K resistors next to the terminal strip turned out to have leads that were too short.)
Soldering point to point can be quite a challenge in cases like this one (the right-hand lug). Four resistors and a hookup wire meet on the same lug of a terminal strip. The trick is to get the lug very hot, very quickly. It also helps to use gravity to help prevent the molten solder from drifting down to the bottom of the lug. I found it was best to put the board on its side before soldering, as shown above.
I also changed my soldering practices as concerns vulnerable components such as transistors. This time, I did one soldering pass for all components *except* the transistors. Then, I added the transistors and, using a heat sink, soldered them on their own, with minimal heat (without melting the earlier joints on the same lug). The result is an "uglier" soldering job but more effective I think. In the above photo, the transistors are about to be soldered. Hey, it's not often that you see "RCA" on a newly soldered discrete transistor nowadays, eh?
Battery installed and ... it works! Only two issues. The tone was too low, because I had substituted a 47kpF capacitor for a 100kpF one as C3 in the headphone output circuit, thinking that the tone was set only by the caps in the earlier sections of the circuit but I was wrong. So I wired another 47kpF capacitor in parallel and the tone was now correct. The other problem is that the volume in the high impedance headphones was too high -- dangerous for one's hearing. After some experimentation, I added the 75K resistor shown above, lowering the volume nicely. Meanwhile, in the latest episode of "outstandingly stupid things that Martin does during each homebrew project" I had let an alligator jumper cable short out the 9V battery and it sat on the bench in that condition for about 10 minutes. When I picked up the battery, it was too hot to touch! I wonder if you can start a fire with a 9V battery? I suspect the answer is "yes." My benchtop is wood, covered with white poster board.
My complete vintage Morse training set. Code oscillator. Ameco key (a J-38 clone) with custom adjustments (I replaced the spring, which was too stiff). High-impedance headphones, which I am beginning to consider as instruments of torture. After wearing them for an hour or two monitoring the bands, the ears hurt, from the combination of hard bakelite and vigorously sprung head strap. While listening to the CW on 40m, I get so absorbed that I don't notice the pain until I turn the set off!
If you don't have old-fashioned high impedance headphones, use an audio output transformer. This one is available at Radio Shack for about $3. It's part number 273-1380.
Closeup of output transformer.
Info on Radio Shack transformer package.
This is a Morse inker that I built as a 9-year-old. (It's not a photo of the actual one I built, but a photo from the Meccano/ErectorSet instruction book.)