1. RADIO WAVE BAND
The radio wave bands used in radio broadcasting are as follows:
LF: Low Frequency
MF: Medium Frequency
HF: High Frequency
VHF: Very High Frequency
2. SERVICE AREA
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.
3. RECEPTION PROBLEMS
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.
This type of interference is called "fading".
Multipath occurs when a signal from the broadcast transmitter antenna bounces off buildings and mountains and interferes with the signal that is received directly.
4. NOISE PROBLEMS
(a) Questionnaire for nose: It is very important for noise trouble shooting to have good understanding of the claims from the customers. Refer to the following questionnaire to diagnose the problem accurately.
Noise occurs at a specific place.
Strong possibility of foreign noise.
|Noise occurs when listening to faint broadcasting||There is a possibility that the same program is broadcasted from different local stations, and that might be listening a program from other station.|
|Noise occurs only at night.||Strong possibility of the beat from a distant broadcasting.|
|Noise occurs while driving on a partic- FM ular area..||Strong possibility of multipath noise and fading noise caused by the changes of FM waves.|
HINT: In the condition of noise occurrence does not meet any of the above questionnaire, check the problems to "Reception Problem" on the previous page.
(b) Matters that require attention when checking:
When extremely loud noise comes into the radio, check if the grounding is normal where the antenna is installed.
(c) Antenna and noise: Electronic signal received by the antenna will reach to the radio transmitting through the core wire of the coaxial cable. Any noise wave other than radio wave is mixed into this core wire, that naturally causes noise in the radio and poor sound quality. In order to prevent the noise from coming into radio, the core wire inside the coaxial cable is covered with a mesh wire called shield wire which transmits the noise to the ground.
5. COMPACT DISC PLAYER
Compact Disc Players use a laser beam pick-up to read the digital signals recorded on the CD and reproduce analog signals of the music, etc.
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.
NOTICE: CD players use an invisible laser beam which could cause hazardous radiation exposure. Be sure to operate the player correctly as instructed.
6. Tape player/head cleaning: MAINTENANCE
(a) Raise the cassette door with your finger.
Next, 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. CD player/disc cleaning: MAINTENANCE
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.
NOTICE: Do not use a conventional record cleaner or anti-static preservative.
8. OUTLINE OF AVC-LAN
(a) What is AVC-LAN? AVC-LAN is the abbreviation, which stands for Audio Visual Communication-Local Area Network.
This is a unified standard co-developed by 6 audio manufactures associated with Toyota Motor Corporation.
The Unified standard covers signals, such as audio signal, visual signal, signal for switch indication and communication signal. Radio receiver assembly and RSA (Rear Seat Audio) panel have a resistance (60 - 80 W) required for communication.
(b) Objectives Recently the car audio system has been rapidly developed and functions have been changed drastically.
The conventional system has been switched to the multi-media type such as a navigation system.
At the same time the level of customers needs to audio system has been upgraded. This lies behind this standardization.
The concrete objectives are explained below.
(c) The above descriptions are the objectives to introduce AVC-LAN. By this standardization, development of new products will no longer cause systematic errors.
(w/ Navigation system (DI-1263 )