Radio, Stereo, and Compact Disc: Description and Operation
DESCRIPTION1. RADIO WAVE BAND
The radio wave bands used in radio broadcasting are as shown:
2. SERVICE AREA
a. There are great differences in the size of the service area for AM and FM broadcasting. Sometimes FM stereo broadcast cannot be received even through AM can be received very clearly.
FM stereo has the smallest service area, and it also picks up static and other types of interference ("noise") easily.
3. RECEPTION PROBLEMS
HINT: Besides the problem of static, there are other problems, such as "phasing", "multipath" and "fade out". These problems are caused not by electrical noise but by the nature of the radio waves themselves.
a. Phasing
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 "phasing".
b. Multipath
Interference caused by reflection of radio waves against obstructions is called "Multipath". Multipath occurs when radio signals emitted from the broadcast transmitter antenna are reflected against tall buildings or mountains and interfere with other signals which are to be received directly.
c. Fade Out
Because FM frequency is higher than that of AM, FM radio wave tends to be reflected against obstructions such as tall buildings or mountains. For this reason, FM signals often seem to gradually disappear or fade away as the vehicle goes behind those obstructions. This phenomenon is called "fade out".
4. NOISE PROBLEMS
a. It is very important to understand a customer's claim clearly for noise troubleshooting. Use the table to diagnose the phenomenon.
HINT: If the condition where the noise occurs does not meet any of the above, find out the cause based on "Reception Problems". Refer to the description about multipath and phasing mentioned previously.
5. COMPACT DISC PLAYER
a. Compact Disc (hereafter called "CD") Players use a laser beam pick-up to read the digital signals recorded on the CDs and reproduce analog signals of the music, etc. There are 4.7 in. (12 cm) and 3.2 in. (8 cm) discs available for the CD player.
HINT: Never attempt to disassemble or oil any part of the player unit. Do not insert any object other than a disc into the magazine.
NOTE: CD players use an invisible laser beam which could cause hazardous radiation exposure. Be sure to operate the player correctly as instructed.
6. MAINTENANCE
Tape Player / Head Cleaning:
a. Raise the cassette door with your finger.
Using a pencil or similar object, push in the guide.
b. Using a cleaning pen or cotton applicator soaked in cleaner, clean the head surface, pinch rollers and capstans.
7. MAINTENANCE
CD Player / Disc Cleaning:
If the disc gets dirty, clean the disc by wiping the surface from the center to outside in a radial direction with a soft cloth.
NOTE: Do not use a conventional record cleaner or anti-static preservative.
8. COMMUNICATION SYSTEM
a. Components in the audio system communicate each other through the AVC-LAN. (Radio receiver with CD changer control function)
b. The master component of the AVC-LAN is the radio receiver assy with a resistance (60 to 80 Ohms), which is necessary for communication.
c. When a short circuit or circuit breakdown occurs in the AVC-LAN circuit, the audio system does not operate normally due to the communication cutoff.
9. DIAGNOSIS FUNCTION
a. The audio system has a diagnosis function (The diagnosis result is displayed on the LCD of the radio receiver assy). (Radio receiver with CD changer control function)
b. The component code (physical address), or three-digit number (in hexadecimal) is set for each component comprising the AVC-LAN.
c. The logical address, or two-digit number (in hexadecimal) is set for each function and component unit in each component.