This alarm siren circuit has a latch. We found it in an article in the January 1975 Radio Electronics magazine. Note the power given by Rx and the speaker. It can be increased by changing Q1.
This field strength meter is intended for the VHF range, above 100MHz. The lowest voltage or...
We found this circuit in an English publication in 1976. The circuit is based on the use of a...
This antenna tuner was found in a 1995 publication in the 1993 Electronics Hobbyists Handbook. The coil...