How this circuit works?

 

Blocking oscillator driving a step-up transformer. Hard to buy that transformer ready-made or to wind your own...
That thing will kill radio reception within 1/4km due to the RFI it generates.

 

Blocking oscillator driving a step-up transformer. Hard to buy that transformer ready-made or to wind your own...
That thing will kill radio reception within 1/4km due to the RFI it generates.

The 3055 is a very old transistor that's just about good enough for (almost) decent Hi Fi. Its frequency limitation should keep the RFI down to a dull roar.

There are many later power transistors that can produce significant RFI in a circuit like that. Even TV horizontal output transistors with their low gain can be made to work in that kind of circuit, and are very capable of generating loads of RFI.

Use a closed core ferrite for the inductor and keep all wiring as short as possible, and the results should be at least tolerable.