When you get to a certain age, you get unsettled by people calling “your” music oldies. That’s how a few of us felt when we saw [Mikrowave1’s] video about Retro QRP – Solid Gold Years (see below). “QRP” is the ham radio term for low power operation, and the “solid gold” years in question are the 1960s to 1980. The videox has some good stuff, including some old books and some analysis of a popular one-transistor design from that time. He even tries a few different period transistors to see which works best.
[Mikrowave1] talks about the construction techniques used in that time frame, old transistors, and some vintage test equipment. You can even see an old ARC-5 command receiver in use to listen to the transmitter. These were made for use in military aircraft and were very common as surplus.
After analyzing the tiny transmitter with a scope and some other gear, [Mikrowave1] makes a real contact using the transmitter and the ARC-5. With 300 mW, he made a Morse code contact with a station over 375 miles away. Not bad!
At the end, he uses a communication monitor to measure the harmonic output of the transmitter. In one sense, it is considerable, but, of course, the low power limits the harmonics too. Adding a filter (which he does) cleans things up considerably. After showing the better output, he makes a 350-mile contact.
We recently covered a transmitter in a walnut shell, that wasn’t much different. If you want to learn more about how hams use QRP — low power operation — you can check out [Dan’s] post on that subject.