Simplicity at the first. Just like like design of this RF source.
3.1.8 Typical RF Signal Generator from 60's. Schematic diagram.
Next, a simple and reliable RF Signal Generator circuit that covers 99% of my needs. Actually my on a four transistors, but the following schematic diagram clearly shows how it works.
As you can see, RF generated by Armstrong/Meissner oscillator (12AT7 (R side)), which is more commonly known as "Joule Thief" (sorry, another language, but for schematic diagrams does not matter). Name does not matter. The
beauty of this solution is that circuit will work with any
center-tapped inductors (L1-L5). The difference will be only in the
frequency, which is limited by RF properties of the vacuum tube (12AT7).
The following schematic diagram shows how easily it converted to transistors. This is a real circuit, which is slightly adjusted according to the components in my generator (K-SG4160B, picture on the top).
These are in production today, and you can buy it. Interestingly, the block of coils has not changed. They are exactly the same as 60 years ago.
The fun is that everything, that is responsible for RF signal quality, is located on this small board (with 2 transistors, 2SK544 & 2SC1907) attached to a variable capacitor.
And I like it. Not because it's simple, but because it works for many years in a row.
No conclusion here. I need to make another generator, powered by a lithium battery (18650), which covers a range of 120-180MHz,AM. If everything works out, then short story about it will be here.
Just in case. If you need a schematic diagram / manual for SG-4160B, then it is on: https://elektrotanya.com.
Yes. It's all simple like that.