This circuit uses a diode as a radiation sensor. The operational ones are old because the publication is from the 80's, but modern low voltage equivalents can be tested.
This is the basic full-scale circuit of an LM3914 for voltage measurement or voltage triggering and...
We found this circuit in the October 1992 Radio Electronics magazine. The frequency is given by C1...
Although most common piezoelectric transducers have a reduction in performance at frequencies...