Found on an 80's Elektor, this circuit uses common components, being the diode a general purpose germanium. The coils select the frequency range of the indicator that reaches 60 MHz.
This simple electronic music box circuit was found in the April 1985 issue of Radio Electronics. The...
This circuit was found in an Electronics Now of the 80s applying to NiCad batteries of the time....
The power source shown for powering for small TTL circuits was found on a Radio Electronics...