The height of both radiators is 195 m. The masts are of lattice structure and surrounded by a cage of six ropes of aluminium. The spacing between mast and cage is 5 m. Every mast is grounded ( no base insulator ) and seperated in two parts by an insulator at the height of 90 m.
The cage around the upper part of the mast extends from the feeding point of 90 m to the height of 165 m.
This cage is connected to the feeding point at 90 m and open at the height of 165 m.
The cage length of 75 m corresponds to l/4 for 1008 kHz. The mast as an inner conductor and the cage as an outer conductor form a coaxial line, at the open end of which at the heigt of 165 m an infinitve reactance exists. By this the top of the mast beyond the cage is nearly disconnected for 1008 kHz. The typical current distribution of a 5/8 l antenna ends at 165 m.
For 747 kHz the length of the coaxial line is shorter than l/4
and represents therefore an inductivity in series, which connects the top of the mast with the rest of the radiator. The current distribution has an irregularity at the height of 165 m. (see drawing below) ( continued on 5E