Beat buzzer
A beat buzzer is an electronic circuit of high frequency technology with which a sinusoidal oscillation with a low frequency (typically in the audible frequency range) is generated from the mixture of two closely spaced sinusoidal oscillations of high frequencies. It consists of two high frequency oscillators with:
- fixed frequency f const and
- variable frequency f var ≠ f const .
The oscillations of both oscillators are mixed, resulting in the sum and difference frequency (useful signal) with the frequency f = f const - f var . The sum frequency with f = f const + f var is in the high frequency range and does not reach the output. The differential signal reaches an amplifier via a level control (potentiometer or volume control) and is available at the output. By changing f var using a variometer or variable capacitor , the output frequency can be varied continuously over a wide range (large in the sense of large relative changes) with largely constant amplitude .
Beating buzzers were used as laboratory equipment to generate low-frequency sinusoidal oscillations of a defined frequency and amplitude.
The area of application for beat buzzers were also early electronic musical instruments such as the theremin or the ondes martenot .
In the radio technology , the same procedure is used when in a superheterodyne receiver , a CW make audible signal or a SSB signal want to demodulate. The additional oscillator has the task of replacing the suppressed carrier (in the vicinity of the intermediate frequency ). The additional oscillator is called BFO for short, English beat frequency oscillator.
Web links
- Beat frequency oscillator with integrated operational amplifiers in DIY
- Adjustment of a tube-operated beat buzzer