välitaajuus

Välitaajuus, often translated as intermediate frequency or IF, is a fundamental concept in radio and electronic receiver design. It represents a frequency that a radio signal is converted to for processing within a superheterodyne receiver. The incoming radio signal, which can vary widely in frequency, is mixed with a locally generated signal from a voltage-controlled oscillator, known as the local oscillator. This mixing process produces sum and difference frequencies. One of these difference frequencies is selected as the intermediate frequency.

The primary advantage of using an intermediate frequency is that it allows for highly selective and stable amplification and filtering. By down-converting all incoming radio frequencies to a single, fixed intermediate frequency, the receiver's amplification and filtering stages can be optimized for this specific frequency. This is much more efficient and effective than trying to design tunable amplifiers and filters that can handle the entire range of potential incoming radio frequencies. The IF stage typically provides the majority of the receiver's gain and its selectivity, determining how well it can distinguish between desired and undesired signals. Common intermediate frequencies include 455 kHz for AM receivers and 10.7 MHz for FM receivers, though other values are used depending on the application.