Found in the 1975 RCA tube manual, this circuit appears elsewhere in this section. The circuit uses contemporary components and is powered by the power grid.
Here is a simple source without a transformer for currents up to 50 mA. The voltage depends on the...
We found this circuit in an old QST magazine. The circuit is powered according to the thermostatic relay...
This simple field strength meter is from a transistor book from the 60's. The transistor is made...