This filter circuit for active frequency divider applications was published in the December 1957 Radio Electronics magazine. The supply voltage is indicated.
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...