Re: Permeability Tuning
Just as an aside, the problems associated with varying the resonant frequency of a tuned circuit (i.e. the variables) point to the main advantage of the superheterodyne set, namely that it's the I.F amplifier (a fixed frequency amplifier) that determines most of the important characteristics of a receiver.
The design of the I.F. amplifier is greatly simplified by the fact that it a fixed frequency amplifier. The designer has much greater control over things like gain, bandwidth, bandpass shape and stability etc.
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