This 8-tube amplifier with 12 W output was found in an American publication from 1947. The output is in counterphase with pentode tubes.
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...