What does beat cut mean on a stereo?

Question

My stereo has beat cut A and beat cut B. I don't know which one to put it on, can someone tell me what they mean?

Answer 1

It's basically an FM interference filter. In some rare circumstances when two FM stereo stations are strong enough and close enough on the dial, some strange noises can occur as a result. Here's an excerpt from a patent that speaks about beat cut filters in FM radios:

The unwanted signal interferes with harmonics of the sub-carrier to creat a beat which is of an audio frequency, thereby leading to reception interference. More particularly, when the 38 KHz switching signal supplied to the decoder of the stereo demodulator circuit takes the form of a rectangular wave, this switching signal contains many components of harmonics in addition to the 38 KHz fundamental wave component. Odd harmonics components interfere with the unwanted signal to create the beat which causes uncomfortable noises. Especially, the third harmonic is serious. Conventionally, a beat cut-off filter or a low-pass filter called a anti-birdy filter is inserted in the composite signal line to lower the level of the unwanted spectrum and reduce the beat. This conventional approach is unsatisfactory since frequency characteristics of the beat cut-off filter or the anti-birdy filter affect the separation of the left and right channel signals and frequency characteristics of the demodulated output.

The adverse phenomenon set forth above takes place when frequencies of two stations are close to each other, the frequency of a desired station and the frequency of another station are intermodulated so that an apparent frequency of the desired station falls in the proximity of the frequency of another station, and the receiver set is interiorly provided with an oscillator.