Section 825 (Audio System): Description

The radio wave bands used in radio broadcasting are as follows:

Fig 1: Radio Wave Bands Graph

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LF: Low Frequency

MF: Medium Frequency

HF: High Frequency

VHF: Very High Frequency

There are great differences in the size of the service area for AM and FM monaural. Sometimes FM stereo broadcasts cannot be received even through AM can be received in very clearly. Not only does FM stereo have the smallest service area, but it also picks up static and other types of interference ("noise") easily.

Fig 2: Identifying Service Area

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Besides the problem of static, there are also the problems called "fading", "multipath" and "fade out". These problems are caused not by electrical noise but by the nature of the radio waves themselves.

Fig 3: Identifying Fading

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• Fading

  Besides electrical interference, AM broadcasts are also susceptible to other types of interference, especially at night. This is because AM radio waves bounce off the ionosphere at night. These radio waves then interfere with the signals from the same transmitter that reach the vehicle's antenna directly. This type of interference is called "fading".

• Multipath

  One type of interference caused by the bounce of radio waves off of obstructions is called "multipath". Multipath occurs when a signal from the broadcast transmitter antenna bounces off buildings and mountains and interferes with the signal that is received directly.

  Fig 4: Identifying Multipath

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• Fade Out

  Because FM radio waves are of higher frequencies than AM radio waves, they bounce off buildings, mountains, and other obstructions. For this reason, FM signals often seem to gradually disappear or fade away as the vehicle goes behind a building or other obstruction. This is called "fade out".

  Fig 5: Identifying Fade Out Signal

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1. Raise the cassette door with your finger.

   Next, using a pencil or similar object, push in the guide.

2. Using a cleaning pen or cotton applicator soaked in cleaner, clean the head surface, pinch rollers and capstans.
   Fig 6: Identifying Pinch Rollers

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If the disc gets dirty, clean the disc by wiping the surface from the center to outside in the radial directions with a soft cloth.