MPX-Filter

The so-called MPX filter is an existing on some cassette recorders and tape recorders notch filter, which can be optionally switched on.

The filter removes the 19 kHz pilot tone and the 38 kHz subcarrier of an FM stereo signal and is required if you want to take a picture of an FM transmitter to an antenna or cable to the recorder, the receiver these frequencies but not sufficiently suppressed.

The abbreviation " MPX " stands for " multiplex " and refers to this pilot tone underlying FM multiplex standard.

The filtering of these frequencies is important for cassette recorder, although many people can listen to the 19 kHz tone (no longer). In a recording of this signal, however, on magnetic tape this ever existing pilot tone would provide an unnecessary magnetization of the band with 19 kHz. In addition, often occur intermodulations on of these two signals and their harmonics with the deletion frequency of the recorder, which is noticeable by a very annoying whistling.

Without adequate filtering of the pilot tone and the function of noise canceling system like Dolby may be affected, since this is interpreted as the pilot tone high (useful) tone.

When recording from other sources, such as CDs should remain this filter off, it is only relevant for the reception of FM stereo sources, and even then only if not already, the receiver performs such filtering. For playback of cassettes of this filter does not matter.

  • Filter ( Electrical Engineering)
  • Transmission technology
585184
de