This sophisticated remote field strength meter circuit was found in a 73 magazine for radio amateurs from the1990s. The circuit measures signals in the 1650 kHz range.
This linear oscillator was found in a 1968 publication. The operational amplifier is from that...
This circuit was found in Radio Electronics from May 1965. The SCRs and transistors are from that...
This Wien bridge circuit, using a 741 operational amplifier, was suggested by Texas Instruments in its 1996...