AM antennas on cars and portable transistor radios are usually vertical. Why?

sequoianoir

AM antennas on cars and portable radios are NOT mounted vertically. The AM antenna is inside the radio in most cases and consists of a ferrite rod inside a coil. The telescopic aerial (antenna) is for FM / VHF reception and its length approximates a quarter of the wavelength of the radio waves in the FM band (88-108 Mhz). Vertical positioning on a car tends to be 'the only choice' since it needs to be mounted at right-angles to the 'ground plane' and clear of the body of the vehicle for best reception. It would work horizontally (see note below) but would really need mounting on the sides or front or back which in reality is not practical. In the UK most FM radio transmissions are broadcast in 'mixed polarity' although some are only vertically or horizontally polarised. For best reception the antenna should be in the same orientation as the transmitter. Note: Some cars have horizontal FM radio antennas but to look at you would think the car did not have an aerial at all. Why? Because the antenna is built into the rear window! It can use the 'wires' that are part of the demisting system - the heated rear window. Dec 04 02, 5:44 PM