Found in documentation from 1924, this 4-tube circuit has a heterodyne amplifier, as it was called.
This circuit is from a Popular Electronics of December 1993. In it we have the way to externally connect...
With this power supply it is possible to use automotive devices with currents up to about 8A on the...
This circuit was found in a 80’s American documentation. The adjustment trimpot is from 47k to...