How does a car stereo system work?
Signals in the AM and FM bands are transmitted through repeaters located around the city. The signals coming from them are received by the vehicle's antenna. When a strong radio signal arrives at the radio antenna, a modern audio system provides high quality playback. However, in some cases the incoming signal is not strong or clear. This may be due to distance from the radio station, proximity to other radio stations, or the presence of buildings, bridges, or other large objects in your area.
Generally, reception of AM signals is better than FM signals. This is because AM radio waves are transmitted at low broadcast frequencies. Long, low-frequency radio waves can propagate in the atmosphere both in a straight line and around the curvature of the earth's surface. Moreover, they can go around various objects and can provide better radio coverage. As a result, clear reception of AM signals can be achieved over longer distances better than FM reception.
AM radio wave propagation
Radio waves in the FM band are transmitted at high broadcast frequencies and cannot go around the earth's surface. As a result, FM radio waves generally begin to weaken at a short distance from the transmitting station. Radio waves in the FM band are more affected by buildings, mountains, or other objects. This may result in poor playback quality and may be mistaken for a radio malfunction. The following conditions are normal and do not indicate a malfunction of the radio:
FM radio wave propagation
Propagation of FM radio waves in different areas
– attenuation – with increasing distance of the car from the transmitting antenna of the radio station, the power of the radio signal drops, and the sound begins to fade. In this case, it is recommended to select another station with a stronger signal;
The occurrence of signal attenuation in the FM band with an increase in the distance of the car from the transmitting antenna of the radio station
– constant buzzing noise – a weak FM radio signal or large obstacles between the radio transmitter and the car's receiving antenna cause interference in the form of a constant buzzing noise. This effect can be reduced by lowering the tone control level in the treble region;
– signal mixing – as the signal in the FM band weakens, another stronger signal with a similar broadcast frequency may appear. This happens when the tuning system is working for the clearest possible signal from the radio receiver. In this case, switch to another station with a stronger signal;
The occurrence of mixing signals as the signal in the FM band weakens and another stronger signal appears with a similar broadcast frequency
– Interference noise – When radio signals from different directions hit the car antenna, it can cause a constant buzzing noise. This can be caused by the direct signal of the radio station and the reflected signal of one broadcasting station or two signals from stations broadcasting at close frequencies on the car's antenna. In this case, switch to another station until these conditions disappear.