NARROW_BAND_FM_RECEIVER

Published:2009/7/9 22:19:00 Author:May | From:SeekIC

The local oscillator is crystal-controlled and the i-f swing is hardly compressed. The deviation of the transmitted carrier frequency, because of modulation, must therefore be limited to prevent severe distor-tion of the demodulated audio signal. The component values result in an i-f of 4.5 kHz and an i-f bandwidth of 5 kHz. If the i-f is multiplied by N, the values of capacitors C17 and C18 in the all-pass filters, and the values of filter capacitors C7, C8, C10, C11, and C12 must be multiplied by 1/N. For improved i-f selectivity to achieve greater adjacent channel attenuation, second-order networks can be used in place of C10 and C11.



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