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9-2: Superheterodyne Receivers
The output of the mixer is an IF signal containing the same modulation that appeared on the input RF signal.
The signal is amplified by one or more IF amplifier stages, and most of the gain is obtained in these stages.
Selective tuned circuits provide fixed selectivity.
Since the intermediate frequency is usually lower than the input frequency, IF amplifiers are easier to design and good selectivity is easier to obtain.