Interior Comfort; Audio System; Weak signal noise- Page 157

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Interior Comfort

Audio System

Form No. 8R29-EA-02I

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.

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.

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.

Weak signal noise

In suburban areas, broadcast signals 
become weak because of distance from 
the transmitter. Reception in such fringe 
areas is characterized by sound breakup.

Ionosphere

100—200 km (60—120 miles)

FM wave

FM wave

AM wave

Direct

Reflected wave

J56J_8R29_EA_02I_Edition4.book  Page 17  Monday, April 21, 2003  3:44 PM