No 9 Final Comments .  


Our model receiver over the last few pages is representative of a small portable radio that you might buy for a few pounds from Comet, Currys et al but it does not have any particularly refined features that you might find on the top end sets.  We did not have automatic gain control, for instance, nor a tone control.


Were this a receiver for Citizen’s Band or for Amateur Radio we would certainly have a squelch control, and  controls for single sideband.


For a digitally tuned set (as opposed to a digital receiver) we would have an entirely different front end altogether, in that far from being controlled by a turned capacitor the frequencies of resonance and oscillation would be controlled by a voltage dependent device such as a varicap diode (which depends on the voltage for its capacitance) and the potentiometer controlling the voltage would be a digital one.


AM and FM may not much longer be with us in the UK as the drive is to go all digital. This is somewhat of a different technology, and although RF  and audio stages are still needed , demultiplexers and decoders follow and there is no real need for full superheterodyne principles.


All of which goes to show the march of progress- radio technology has come a long way since Armstrong’s day, and further still since Fessenden’s.











This is the end of the Receiver Explanations Section and of Radio Principles.

Written by Ian Lang Oct 2010 Last update Oct 2010

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Radio Principles