Answer 7—To give a specific example, the AM broadcast band covers roughly 530 to 1,700 kHz, a frequency ratio of 3.2, which requires a capacitance ratio of 10.3 to tune. With an IF of 455 kHz, a high-side LO can run from 985 to 2,155 kHz, a frequency ratio of just 2.2, requiring a capacitance ratio of 4.8 to tune.

Contributor: David Tweed