5.2. FREQUENCY MODULATION (FM)

Here the term itself shows already how it is achieved: The carrierwave in this case has an always constant amplitude. If there is no audiosignal there will be broadcasted exactly the basical carrierfrequency CF (for example 10 MHz.).

As soon as there is an AF-signal coming in, this carrierfrequency will be varied.

If there is coming in a positive halfwave of the audiofrequency the carrierfrequency will be increased. This rise can reach a maximum of 75 kHz in case of the highest permitted amplitude of the AF-signal. This means the outgoing signal will be 10.075 MHz in case of a maximum positive amplitude.

fig. 28

If there is a negative halfwave coming in, the carrierfrequency will be diminished.. As soon as the audiosignal has reached again “0” the outgoing signal has exactly the original frequencao of 10 MHz.