# How tuning of particular FM signal is done?

I have a transistor radio which has facility to play FM radio channels between 88MHz to 108MHz frequencies. Now,consider a situation ,there are five FM stations which I can hear in my city 91.1MHz,93.3MHz,94.3MHz,98.3MHz and 102MHz.

Neglect all other signal like video signals,mobile phone signals, noises , distortions for a while. Consider that there are only 5 FM signals in the air. All of 5 FM radio stations will transmit their respective frequency components from their base stations and therefore at the antenna of transistor radio there will be sum of the 5 frequency components.

Now, let us consider a function which contains summation of above 5 given FM signals present at the antenna. When I try to tune my transistor radio manually ,the transistor radio has to choose only one frequency component from the above function.

Here, I want to learn how transistor radio does this with the help of frequency domain analysis. Can anybody explain the tuning of transistor radio using Fourier transformations for any FM frequency say 98.3MHz? How phase,amplitude and frequency parameters of each FM signal are taken care of while tuning a particular FM frequency say 98.3MHz?

• "a sinusoidal function which contains summation of all given FM signals" - what does that mean? Jun 27, 2015 at 20:16
• @Andy it's function which is summation of 5 given FM signals Jun 27, 2015 at 20:31
• Why do you call it a "sinusoidal function" and not just use plain unconfusing English like... let us consider ONLY these 5 FM signals are present at the antenna? Jun 27, 2015 at 21:08
• Why do you call it a 'sinusoidal function' when it isn't? An FM signal is not sinusoidal, and neither is the summation of five of them. Fourier transforms therefore have nothing to do with it either. Jun 28, 2015 at 0:00
• @EJP I have edited my question . All of 5 FM radio stations will transmit their respective frequency components from their base stations and therefore at the antenna of transistor radio there will be sum of the 5 frequency components. Jun 28, 2015 at 10:21