Pre selector (T435E)

This circuit was found in a 1938 Radio Handbook. The source is not given and the table for the coils is next to the diagram. The tube is an 1851.

50 ohm Line Driver LM3900 (CB5056E)
The gain of this amplifier is 10 times and the excursion to the output voltage is 6.0 V (peak to...
Transistor gain meter (CB20522E)
This circuit was found in a publication in the 1950s, mainly applying to germanium transistors of the...
Simple MW Radio 2 (CB4360E)
Originally this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...