Re: Determining volts/meter

["Eric Cowdrey" <Eric.Cowdrey@CANCERCARE.MB.CA>]

To answer your specific question, you could make some estimate of the electric field strength in the "far field" region of the antenna. This requires assumptions about the information you have provided:



First, assume that the antenna radiates power (P) isotropically. Then, the power density (W) in the "far field" at a distance, r, is:



W = P/4 x pi x r**2, where pi is 3.14.



You can then calculate the equivalent electric field strength (E) from the relationship, W = E**2/Z, where Z is the impedance of free space = 377 ohms.





Eric Cowdrey, M.Sc. (Physics)

Radiation Protection Officer

Department of Medical Physics

CancerCare Manitoba

675 McDermot Avenue

Winnipeg, Manitoba  R3E 0V9

Canada



Tel (204) 787-2166

Fax (204) 775-1684

mailto:Eric.Cowdrey@cancercare.mb.ca



Industrial hygiene in Manitoba: http://aiha.cancercare.mb.ca

Radiology in Manitoba: http://www.umanitoba.ca/faculties/medicine/radiology



>>> "Jenkins, Ken A." <KAJENKIN@SOUTHERNCO.COM> 08/27/01 06:56AM >>>

Hi all,

I need a little explanation from any instrumentation/electronics folks out

there.  I've been reading about cell phone interactions with dosimeters

including ANSI N42.20-1995 which says, "The variation of response shall not

be greater than * 10% when the electromagnetic radiation field strength of

100 Vm-1 at frequencies above 100 kHz to 500 MHz and 1 Vm-1 at frequencies

above 500 MHz to 1 GHz".  My question is, if I know the cell phone frequency

and transmitter power in watts, how do I calculate volts/meter? Is this

possible or do I need more information? Any help will be greatly

appreciated.



Ken Jenkins

Health Physics Instructor

Southern Nuclear Operating Company



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