Subject: Re Double exposure (Leifheit)(Cherry)(Curry).
Date: Mon, 20 Nov 2000 235734 -0600
From: Roy Beavers
To: guru
--------------------------------------------------
........Response from EMF-L.......
I forward this extremely technical item only to ensure that our techies
get it and get a chance to participate..... Please continue this
discussion direct within the technical community and off-line of EMF-L....
....guru.....
-------- Original Message --------
Subject: Re: Double exposure (Leifheit)(Cherry).
Date: Mon, 20 Nov 2000 12:33:50 -0600
From: "Bill P. Curry"
To: roy@emfguru.com
References: <3A18D7D4.B318F8A@emfguru.com>
Roy and Neil,
I think the usual practice is to add antennas that are far enough apart
not to be in each other's near field. Otherwise, the frequencies of the
resultant radiation would be the sum of the primary frequencies of the two
separate RF sources and the difference of these two frequencies. This would
not be good practice for communications links. Putting two RF sources at a
spacing of several wavelengths (of the lowest frequency source) will generally
avoid this problem and allow the intensity (radiation density) of the two
sources to be added linearly, instead of adding the fields.
My concern is whether, in the presence of a ubiquitous low frequency field
(wavelength longer than the RF tower height) might not allow the RF power
density to be magnified, because of the addition of the RF electric field to
the low frequency field. If the frequency of the low frequency field is
sufficiently low, the sum and difference frequencies of the resultants field
will differ negligibly from the original RF frequencies, so the human body
will perceive the resultant radiation to be the original RF radiation, but at
an enhanced radiation density - provided the strength of the low frequency
field exceeds the strength of the original RF field.
The paper that I delivered in Salzburg last June at the International
Conference on Cell Tower siting considered this problem, using a formulation
due to A. Sommerfeld (1925) for the mathematical description of the ground
wave from a low frequency AM broadcast source whose wavelength was
sufficiently large to submerge both terrain variations and the microwave
sources on the cell phone tower under consideration.
The significance of the ground wave is the fact
that it dies off with distance more slowly than the conventional sky wave
radiation from a point source, and it has the same polarization as the field
from a cell tower antenna. This means that the electric fields of the low
frequency ground wave and the microwave source are pointed in the same
direction; hence, the fields may then be added linearly, and the resultant
radiation density will be proportional to the product of the low frequency
field strength and the microwave field strength.
The key to this amplifying
mechanism is the requirement that the low frequency source must be stronger at
the location of interest than the microwave field. This is why I chose to
consider the low frequency source to have so low a frequency as to produce a
substantial ground wave. I would expect a similar amplification, however,
when a cell phone antenna is hung on a broadcast tower - AM, FM, or TV -
provided only that the electric fields have to be parallel to the field of the
low frequency source.
I invite your comments about this mechanism of amplifying RF radiation.
Roy Beavers wrote:
> .........Response from Dr. Cherry......
>
> He says the double exposure calculation is off by half.... i.e., It
> SHOULD BE FOUR TIMES!!!..... He's probably right.... Any more argument?
> Clas, Alasdair, Bill, et. al.........guru......
> (Now, consider what happens when the NEXT pair of antennae are added???)
>
> -------- Original Message --------
> Subject: RE: Double exposure (Leifheit).
> Date: Mon, 20 Nov 2000 20:22:19 +1300
> From: Neil Cherry
> Reply-To: "neil.cherry@crc.govt.nz"
> Organization: Canterbury Regional Council
> To: "'roy@emfguru.com'"
>
> Dear Roy,
>
> As we know the power density (microwatts/sq cm) is a function of the square
> of the electric field (S = E^2/3.77) where E is the electric field in V/m.
> i.e. E = 10 V/m converts to S = 100/3.77 = 26.5 microwatts/sq cm. I
> understand that the fields are additive. This would mean that rather than
> adding two equal signals of 26.5 microwatts/sq cm (giving 53 microwatts/sq
> cm) instead we add the two E fields, i.e. 10 + 10 = 20 V/m. This then
> becomes S = 400/3.77 = 106.1 microwatts/sq cm (4 times the power density).
>
> Can any of our engineering experts confirm or correct this ?
>
> Regards
> Neil Cherry
>
> -----Original Message-----
> From: Roy Beavers [SMTP:guru@emfguru.com]
> Sent: Sunday, 19 November 2000 21:08
> To: guru
> Subject: Double exposure (Leifheit).
>
> ............From EMF-L........
>
> Yes, it very likely will double the exposure (approximately)..... P.S.
> There will likely
> be MORE to follow........
>
> That is probably the REAL problem with these towers -- not the first
> lonely antenna
> that is mounted..... But those that follow....... Is that right,
> Sutro Tower????.....guru....
>
> -------- Original Message --------
>
> Subject: cell tower emf
> Date: Sat, 18 Nov 2000 16:52:33 -0500
> From: "Bruce Leifheit"
> To:
>
> DEAR ROY, SPRINT PCS ERECTED A CELL TOWER IN 1998 LESS THAN 100' FROM
> MY HOME. WE TRIED IN VAIN TO HAVE IT STOPPEDBUT AS I WRITE THIS IT IS
> STILL IN APPEAL. I WAS WONDERING IF YOU COULD SHED SOME LIGHT IN LAYMENS
> TERMSABOUT POSSIBLE HEALTH EFFECTS THIS COULD HAVE UPON MY WIFE ,KIDS
> AND I.ALSO AS I WRITE THIS THEY AREADDING A SECOND SET OF ANTENNA AND
> ALL NESCESARY HARDWARE TO PROVIDE FOR A SECOND CARRIER. DOES THIS DOUBLE
> MY FAMILIES EXPOSURE AND RISK. ANY INFORMATION YOU COULD PROVIDE WOULD
> BE GREATLY APPRECIATED.
> SINCERLY
> BRUCE LEIFHEIT
> 3928 STATE ROUTE 225
> DIAMOND, OHIO 44412
> 330-654-3492
> << File: ATT00004.html >>
--
Bill P. Curry, Ph.D. |Physics is fun.
EMSciTek Consulting Co. |Trying to make a living!
22W101 McCarron Road, |Phone: (630) 858-9377
Glen Ellyn, IL 60137 |Fax: (630) 858-9159
____________________________________________________
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Reprinted with permission of Roy Beavers, http://www.emfguru.com