Exposure zones near parasitic elements in high powered antennas

In high powered transmitting antennas which use parasitic elements or have isolated conductive towers and guy lines as part of the structure, it is important to know if the region immediately behind the parasitic structures has significantly reduced radiation exposure. The reason of this investigation was to assess radiation levels with and without a human present in this zone and the effect on the radiation characteristics of the antenna. It is well known that a parasitic monopole located close to a radiating monopole changes the radiation properties of the antenna. When the parasitic element acts as a reflector, the principal radiation direction is located in the radial plane through the two elements and in the opposite direction to the parasitic element. The effect is significant only when the parasitic element carries significant induced current.