digital signals dramatically increases thus decreasing the frequency deviation at the transmitter is not viable using conventional fm discriminators and pm demodulators in the receiver the present invention allows fm transmitters and receivers in which the frequency or phase modulation of the signal to be transmitted is generated at the transmitting side of a communication channel with a significantly reduced channel bandwidth or very small corresponding frequency deviation the frequency modulated signal is transmitted over the communication channel and received at the receiving side of the communication channel the received signal is mixed with a local oscillator frequency to move the fm signal to the narrow band intermediate frequency the frequency modulated if intermediate frequency signal is applied to the superheterodyne frequency multiplication signal expansion circuit which results in an fm signal with significantly expanded frequency deviation while the fm signal remains centered at the if frequency along with a significantly improved snr signal to noise ratio the frequency deviation expansion at the receiving side of the communication channel is preferably accomplished by utilizing the superheterodyne frequency multiplication signal expansion circuit accordingly the expanded frequency modulated signal can be further processed in any desired manner to obtain the transmitted base band signal thus the reduced bandwidth or reduced frequency deviation fm receiver can reproduce high quality base band audio signals or digital data signals with low ber bit error rate over a bandwidth limited communications channel referring to the drawings the invention is described with reference to an illustrative embodiments as follows 0029 fig1 is a block diagram of the preferred embodiment of an fm frequency modulated transmitter after it 39 s.