The circuit presented is a Japanese commercial radio from the 1960s. With a 4.5 V supply, it is a super-heterodyne type with an IF of 455 kHz. 6 germanium transistors are used.
This circuit was obtained in a Radio Electronics of the 90s. The circuit uses an integrated circuit...
This squelch is activated by its own noise, acting automatically. It is used in communications...
In this circuit of the 1980s, the T1 transformer has 30 turns of 28 primary wire and the secondary...