Fading reducing aerial

A fading reducing aerial is a transmission aerial for long- and mediumwave with a flat radiation pattern in order to push the area of fading far away from the transmitter site. A fading reducing aerial must reduce the radiation power at elevation angels of more then 50 degrees as strong as possible.

In its simplest construction mode it is an aerial of half wavelength. Such an aerial should be as thin as possible. In early days therefore a wire was hung up in a wood framework tower. Nowadays a radio mast is therefore used, which is fed at its foot and in a certain height. Therefore the radio mast must be insulated against ground and be divided by a separation insulator electrically in two parts, where for feeding of the upper part either a cable inside the mast construction or the ladder, which must be mounted insulated is used. The medium wave transmitters Mühlacker, Wolfsheim and Hamburg use such aerials. There are also radio masts for fading reducing aerials with two separation insulator as at Ismaning.

Because such separation insulators are more sensitive as the whole other construction of the radio mast, bigger horizontal forces, which could be generated by wind caused oscillations, should be inhibited. Therefore some radio mast with built in separation insulators have oscillation dampers just above the separation insulator. You find such device at the radio masts of the transmitters Wolfsheim, Hamburg and Ismaning.

An other possibility for reducing a fading-reducing aerial is the usage of dipols hung up in a certain height above ground. A further possibility of the realization a fading reducing aerial is a circle group aerial. Therefore many mast antennae were arranged on a circle and fed in equal phase. With such facilities very flat radiation patterns could be realized, although they are very expensive, because multiple radio masts are required. There was such a facility at longwave transmitter Orlunda in Sweden.