An Untuned Radio-Frequency Amplifier

This paper outlines in brief a number of untuned radio-frequency transformers which have been used in the past. It discusses their characteristics and reasons for their limitations. It is pointed out that if the plate-load impedance of a tube can be increased at the high frequencies, the amplification will be increased. A method of doing this by closely coupling a circuit tuned to a high frequency is analyzed, and the equation for amplification is derived. The construction of a transformer embodying this principle is next described and amplification curves throughout the broadcast band are given for several varieties.