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21.6 Ganging the Oscillator
We have seen that the intermediate frequency is equal to the
difference between the signal frequency and the oscillator
frequency. With an i.f. of 470 kHz, for example, the oscillator must
be tuned to a frequency either 470 kHz greater or 470 kHz less than
the signal.
Suppose the set is to tune from 525 to 1605 kHz. Then, if higher in
frequency, the oscillator must run from (525 + 470) to (1605+470),
i.e., from 995 to 2075 kHz. If, on the other hand, the oscillator is
lower in frequency than the signal, it must run from (525^470) to
(1605-470), or 55 to 1135 kHz. The former range gives 2.09 as the
ratio betwee ...