Makeshift Crystal Radio Output Transformer

This project was part of my initial attempts at homebrewing an output transformer for my  'Loudspeaker Crystal Radio'.

An air-core crossover network inductor and a ferrite-core one (from the junk box) appeared suitable as the primary and secondary windings of the transformer.

An Air-core & a Ferrite Core Crossover Inductor
The large number of turns of the air-core inductor as primary and the small number of the ferrite one as secondary would give a step-down ratio. With luck, the open ferrite core would enable reasonable coupling.

 Simple coupling of the two inductors
Testing was simple, with the air-core inductor hooked up to the crystal radio and the ferrite-core one (placed within) connected  to the speaker.

The result was encouraging enough for further attempts which culminated in a proper 'Crystal Radio Output Transformer'.