Ceramic Filter Beat Frequency Oscillator

BFO is a simple device which helps us to listen SSB and CW transmissions. Reception of SSB and CW signals requires a product detector or BFO (Beat Frequency Oscillator) to reinsert the missing carrier. This circuit is very simple since it requires no turned circuit and hence no adjustment in the BFO circuit. The number of components required is also very limited. To produce 455 Khz carrier a ceramic filter is used. It cost me Rs: 6/- only. The RF choke (RFC) is made by winding 150 turns of enamelled wire on half watt 150 K carbon resistor.

When receiving Single Side Band (SSB) signals the locally generated carrier beats with the SSB signal to produce the complete audio signal. Because the ceramic filter operates at fixed frequency, no turning is required to demodulate the single side band (SSB) signals and no regulated power supply is necessary. First tune your AM radio to some SSB signal and switch on the BFO and slightly adjust receiver turning for good resolved audio quality. To resolve stronger stations connect a wire not bigger than 10 cm to the out put of the beat frequency oscillator.

Most of the BC receivers use 455 KHz as IF amplifier frequency. Some receivers have an IF Frequency which lies between 450 and 460 KHz. For best result the receiver IF amplifier frequency and the beat frequency oscillator frequency should be the same.