Air core transformers
G. L. R. Lowe · Transactions of the South African Institute of Electrical Engineers · 1923
The Air Core Transformer method of amplification requires a fair amount of attention to detail, since should the transformer windings he of unsuitable values very poor amplification will be obtained. In coupling the transformer in circuit the one winding is connected in the plate circuit of the amplifying valve, and the other winding is connected to the grid and filament of the next valve, Fig. 1.