Design of unequal-Q double-tuned transformers

THERE are many instances, in the application of double-tuned transformer coupling, where the primary and secondary Q factors are unequal. When coupling from a crystal converter to the grid of the first intermediate-frequency amplifier, for example, the primary Q is likely to be much lower than the secondary Q. A similar situation exists, if the primary is tuned, when coupling from a transmission line to the grid of a radio-frequency amplifier. An intermediate-frequency interstage transformer, with a damping resistor only across the secondary, may have a high primary Q and low secondary Q.