Insignia IN-CD101 User Manual (English) - Page 15

IGNITION AND INTERFERENCE NOISE Ignition The most common source of noise in reception is the ignition system. This is normally due to the fact that radio is placed relatively close to the ignition system (engine). This type of noise can be easily detected because it will vary in intensity of pitch with the speed of the engine. To reduce the possibility of these problems, ALWAYS FINE TUNE a station, and if possible, set the antenna height to 30 inches. CAUTION Usually, the ignition noise can be suppressed considerably by using a radio suppression type high voltage ignition wire and suppressor resistor in the ignition system. (Most vehicles employ this wire and resistor but it may be necessary to check them for correct operation.) Another method of suppression is the use of additional noise suppressors. These can be obtained from most CB/A mateur radio or electronic supply shops. Interference Radio reception in a moving environment (automobile) is very different from reception in a stationary (home). It is very important to understand the difference. 1. This unit is designed to operate on 12-volts DC, negative ground electrical system only. Do not attempt to install this unit in a vehicle having a positive ground system. 2. You should not touch the high-polished playback head with any metallic or magnetic tools. 3. Your unit has built-in filtering to eliminate most of the noise that might come through the power source. However, with some vehicles, particularly older models, some clicking or other unwanted noise might be present. AM reception will deteriorate when passing through a tunnel or when passing under high voltage lines. Also, noise can be picked up from passing automobiles. Although AM is subject to environmental noise, it has the ability to received at great distance. This due the fact that broadcasting signals follow the curvature of the earth and are reflected back by the upper atmosphere. FM reception is just the opposite of AM. It is not subject to environmental noise and it does have the ability to be received at great distances (usually 30 miles). Also, tall buildings, mountains, or hills can block the FM signal. 15