This circuit is from a 1980s Motorola documentation. The circuit makes use of old components that can in some cases be exchanged for modern equivalents.
Using a common crystal diode and a 741, this circuit can be used to detect microwaves. The circuit is...
The two circuits shown show how to obtain an SSB / CW control for receiving this signal top at a...
The oscillation of the relay causes the applied audio signal to deform and start to resemble the...