Interior Features; Audio System- Page 215

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Interior Features

Audio System

FM characteristics

An FM broadcast range is usually about 

40—50 km (25—30 miles) from the 

source. Because of extra coding needed to 

break the sound into two channels, stereo 

FM has even less range than monaural 

(non-stereo) FM.

FM Station

40—50km 
(25—30 miles)

Signals from an FM transmitter are similar 

to beams of light because they do not 

bend around corners, but they do reflect. 

Unlike AM signals, FM signals cannot 

travel beyond the horizon. Therefore, FM 

stations cannot be received at the great 

distances possible with AM reception.

AM wave

FM wave

FM wave

100—200 km (60—120 miles)

Ionosphere

Atmospheric conditions can also affect 

FM reception. High humidity will cause 

poor reception. However, cloudy days may 

provide better reception than clear days.

Multipath noise

Since FM signals can be reflected by 

obstructions, it is possible to receive both 

the direct signal and the reflected signal 

at the same time. This causes a slight 

delay in reception and may be heard as a 

broken sound or a distortion. This problem 

may also be encountered when in close 

proximity to the transmitter.

Reflected wave

Direct

Flutter/Skip noise

Signals from an FM transmitter move in 

straight lines and become weak in valleys 

between tall buildings, mountains, and 

other obstacles. When a vehicle passes 

through such an area, the reception 

conditions may change suddenly, resulting 

in annoying noise.

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2015/10/21   16:53:50