Beacon with instrument (CB20495E)

This circuit causes an instrument needle to oscillate to signal an event. The circuit is powered by solar panel from 1 V.

Antenna tuner (CB7459E)
Found in a QST from the 90's this circuit is suitable for the medium and short-wave range. |...
Bridge type transistor tester (CB20526E)
We found this circuit in documentation from the 1950s. The circuit basically applies to germanium...
Signal Follower 4001 (CB5890E)
We can also use the 4011 on this CMOS circuit that makes use of a crystal headset. The power...