Subject: AM and longwave questions (Curry).
Date: Thu, 08 Mar 2001 043331 -0600
From: Roy Beavers
To: guru
--------------------------------------------------
........From EMF-L.......
Our RF/MW technical expert has written a rather long -- but
complete and informative -- answer to a question we received
from the Netherlands. You might want to drop down and read
the questions (from Herbert Visser) first. Then come back to
top and read Bill's very informative answers.......guru......
-------- Original Message --------
Subject: Re: [Fwd: AM and longwave]
Date: Wed, 07 Mar 2001 22:47:58 -0600
From: "Bill P. Curry"
Reply-To: BPCurry@MCS.com
Organization: EMSciTek Consulting co.
To: roy@emfguru.com
References: <3AA60686.C44B6B16@emfguru.com>
Roy and Herbert,
I'll try to answer your questions as well as I know how. 1) The frequencies
that you cite for AM and longwave broadcasts are so low that the absorption
coefficient for brain tissue is much lower than it is at the higher
frequencies - such as those used by cell phone systems. (You can find my
absorption coefficient charts on the EMR Network website: www.emrnetwork.org.)
Nevertheless, if the power is as high as you say, you really should estimate
the radiation density and then compare your result with tables of published
biological effects versus radiation density. Cindy Sage compiled a table of
bioeffects versus radiation density and also versus Specific Absorbed
Radiation (SAR) level. She formerly distributed it free, but now she charges
$10 to send you a copy of the full tables. If you can get an estimate of the
radiation density, contact me and I'll see that you get a portion of the
tables that includes the effects that occur at the radiation densities that
you find and the references to the publications in which these results are
reported. 2) If the power is reduced from 600 kW to 10 kW, the radiation
density at the same position will be reduced by a factor of 60, all other
things being the same.
To estimate the radiation density, at the level of accuracy that you can
probably expect to achieve without knowing the characteristics of the antenna
system at 171 kHz, you should take the power in watts and divide it by 4 pi
times the square of the distance (in cm) from the antenna to the locale of
your concern. This will be the radiation density that you could expect from
an omnidirectional source. If you know the directional characteristics of the
source (direction in which it focuses the radiation and gain in that
direction) then multiply the above results by 10^(0.1*g) where g is the gain
(in decibels) in the direction of interest. When the calculation is finished,
multiply the results by 2.56 to account for an average radiation enhancement
based on 60% reflection of the incident electric field by the ground or by
structures. However, if you are located near the sea, the enhancement factor
should be bigger, because the conductivity of salt water is much higher than
that of the ground. Probably, at the antenna location, it is as large as a
factor of 4 (corresponding to 100% reflection of the incident electric field.)
I don't know the distances and locations with which you are concerned, so I
have just given the recipe for doing the calculations. If you wish, I will do
them for you, provided you can obtain the required information.
The tables that I mentioned show clearly that biological effects have been
observed at radiation levels far below the international limits recommended by
ICNRP and the World Health Organization. For example, the US safety limit for
absorbed RF radiation is 1.6 W/kg of tissue, and I assume that the ICNRP limit
is the same or very similar. In contrast, as Swedish research group at Lund
University have observed opening of the blood brain barrier at absorbed
radiation levels 4,000 times less than this value. The consequence of opening
the blood brain barrier is to allow harmful substances (like bacteria)
circulating in the bloodstream to enter the brain. Other biological effects
include breaking DNA molecules excessively at radiation levels 700 times less
than the FCC "safe" level. There are various other effects mentioned in the
table. In addition, from the EMR Network web site, you can download a
compilation of the abstracts of 400 papers published in established scientific
journals since 1995 and dealing with biological effects induced by RF
radiation. These were compiled by Prof. Henry Lai, whose team were the first
to dicover excessive DNA breakage in blood taken from rat brain cells imals
had been irradiated by RF radiation - sometimes for periods as short as 20 minutes.
Let me know if you need any more information
Roy Beavers wrote:
>
> Herbert:
>
> I am forwarding your question to Dr. Bill Curry. He is better
> qualified to address it. However, I should warn you that there
> are many more questions than answers about EMF at this stage of
> the learning process...... Little is actually known for sure.
> Much more research is needed. Until that happens, we are often
> extrapolating from a "little bit of knowledge" to a speculative
> or theoretical answer.......guru.......
>
> -------- Original Message --------
> Subject: AM and longwave
> Date: Wed, 7 Mar 2001 10:08:30 +0100
> From: "Herbert Visser"
> Reply-To:
> To:
>
> Hi Roy,
>
> Great site you've got there !
> Do you happen to know what the negative biological effects could be for AM
> and longwave broadcasting ?
> These are the frequecy's between, roughly 150 and 1700 khz ?
> And then specifically a frequency which is 171 khz ? There's some
> organisation over here willing to
> construct 2 Eiffeltowers (actually taller than the Eiffeltower, 430 meters
> !!) in the Northsea and
> beam a 600 Kilowatt signal towards the UK from a marinebased construction
> off the Dutch coast.
> Environmentalists are trying to stop this project.
> And what would happen if the power would be reduced to, let's say, 10
> Kilowatts omnidirectional ?
>
> Best wishes,
>
> Herbert Visser
> Amsterdam
> The Netherlands
--
----
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
Web page: http://www.EMSciTek.com
____________________________________________________
| Analysis, experiment design & software development |
| for engineering and the physical sciences |
----------------------------------------------------
Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.emfguru.com