• 23 APR 10
    • 0

    #1240: Indirect proof of strong microwave background radiation

    NOTE: The following message from Georgiy Ostroumov is a follow-up to his previous message from March 25, 2010, #1232: Expert warning on increasing microwave exposures”

    From Georgiy Ostroumov, Ph.D.

    My article”¯The most dangerous sources of microwave radiation”¯ had been published (http://www.emfacts.com/weblog/?p=1279) and I have received a few questions from different countries. Some people believe that the situation described in the article may occur only occasionally. I should think that such situation is typical everywhere. The strong background microwave radiation at frequencies above 2.5 GHz is present in many places.

    I shall try to proof it regarding charging of batteries from microwave energy in air.

    Some firms are developing devices (batteries) which could charge from ambient electromagnetic radiation (background electromagnetic fields, background microwave radiation , etc). I think that developers have already measured and calculated everything.

    Let us, and we calculate.

    Markku Rouvala ( a researcher from the Nokia Research Centre, in Cambridge, U.K.) says that his group is working towards a prototype that could harvest up to 50 milliwatts of power enough to slowly recharge a phone that is switched off. He says current prototypes can harvest 3 to 5 milliwatts. Nokia is focusing on harvesting many different signals in frequency range between 500 megahertz and 10 gigahertz (a range that encompasses many different radio communication signals). http://www.technologyreview.com/communications/22764/?a=f

    How much the background microwave radiation is required? Developers are not answering directly the question but we could ourselves evaluate all. Sapienti sat.

    Let surface area of the battery will be equal to 50 cm2(a typical case). Let total power of the background microwave radiation is fully(the best case) converted into DC power. If you expect to get 50 mW DC power, power flux density must be equal to 1 mW/cm2. In other words, the developers are counting on the fact that in many places, long-term background of the microwave radiation has already reached 1 mW/cm2, or in the near future will be about 1 mW/cm2. In accordance with the recommendations ICNIRP (International Commission on Non-Ionizing Radiation Protection), the limit of the power flux density for the frequency of 0.5 GHz is only 0.25 mW/cm2 and 1 mW/cm2 in the frequency range above 2 GHz (see “Reference levels for general public exposure to time-varying electric and magnetic fields”¯).

    By the way, the independent organization “¯Bioinitiative”¯, based on consideration of non-thermal effect, recommends a much lower threshold power flux density for the microwave frequencies, namely 0.0001 mW/cm2(outdoor). From this point of view, even level of the power flux density 0.1 mW/cm2 necessary to produce 5 mW DC power, is unacceptably high.

    In what frequency range is concentrated the largest part of the radiation? To answer this question, I must again refer to the joint statement of the Nordic Radiation Safety Authorities:”¯ According to measurements performed in all the Nordic countries exposure of the general public to these background fields(for radiofrequency range from 10 MHz to 2,500 MHz) is typically far below 1/100th of the exposure limits)”¯. Thus, we can obtain no more than 0.5 mW DC power from the total radiation in the frequency range up to 2.5 GHz. It is likely that a similar situation exists in many other countries. I might add that in Finland total radiation in frequency range up to 5 GHz does not usually exceed 0.0001 mW/cm2. Unfortunately, total radiation in frequency range above 5 GHz can often be very high. Sources of the most powerful background microwave radiation in the frequency range above 5 GHz are radars, radio relay links and terrestrial base stations for satellite communication. It should be borne in mind that frequency ranges of the sources of the background microwave radiation in different countries may vary. Nevertheless, it is hardly expect to find such sources in frequency range up to 2.7 GHz, because of possible interference of mobile communications.

    It is sometimes said, for example, that the microwave radio relay link passes the signal from point to point, so this radiation is not dangerous.

    And so it should be!

    In practice, almost safe system often becomes a source of the strong background microwave radiation. To verify this possibility, simply calculate the background radiation from reflection, taking into account beamwidth (up to 3 degrees). Calculate, for example, a level of a signal reflected from a metal securing a mast at a distance of 20 meters. You will be surprised at the very high level of the reflected signal. This is one of ways to create high-power microwave background.

    On the one hand, this strong background microwave radiation allows the developers to get out of the air 50 mW DC power, but on the other hand presence of such powerful radiation just completely eliminates the precautionary principle(ALARA- As Low As Reasonably Achievable).

    I would like to emphasize that there is no reason to expose the general public exposure of the strong radiation. Moreover, this background microwave radiation can and should be reduced to arbitrarily low values everywhere except in places where the radars are working.

    Georgiy Ostroumov, Ph.D. g_ostroumov@yahoo.com

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