This diagram was mainly used to describe why on a certain building the radiation levels vary from one apartment(say 7th floor) to the apartment above or below (6th and 8th floor) for a building at Khar (West), Mumbai.
The radiation pattern of a cell tower antenna is defined by its lobes. Radiation will be highest from the primary lobes in the horizontal direction. There is also radiation from secondary lobes.As seen in the figure, the readings that will be taken in between the lobes will be much lesser.
As seen in the figure, the radiation will also be high vertically downward from the secondary lobes. This is what most mobile operaters hide or are not aware of in India.
Distance is another critical factor. The power density varies by (1/R2), where R is the distance. People living within 50-300meter radius are in the high radiation zone. The figure below is a study from Germany. In the US, amplifiers of 1-2 Watt each are used in majority of the residential areas. However in India, at many places even 100 to 200 W amplifiers are used and there are clusters of antennas from multiple operators on the roof top of several residential and office premises.
Below is a simulated radiation pattern of a cell tower antenna by Prof. Girish Kumar from IIT Bombay, an expert on cell phone tower radiation and with experience of more than three decades in Antennas and Microwaves.
USHA KIRAN BUILDING - several cancer cases
Through the help of the above typical radiation pattern, let’s analyze the news reported in Mid-day, Mumbai dated Jan. 3, 2010, which stated - “Mumbai's swanky Usha Kiran building says the four cancer cases there could be linked to mobile towers installed on the facing Vijay Apartments”. The picture taken from the Usha Kiran building of the several antennas installed on the seventh floor of Vijay Apartments is shown in Fig. below.
Recently (as on Jan 2011) two more cancer cases have been reported on the 5th and on the 10th floor.
People living in the 6th, 7th and 8th floor in the opposite building will get maximum radiation as they are in the main beam direction. People living on the other floors will receive lesser radiation as beam maxima is reduced considerably as can be observed from vertical radiation pattern. In the horizontal direction again, people living in the front side of the antenna will receive much higher radiation compared to people living in the back side of antenna.