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Mobile Radiation calculation

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  • #60769 Reply
    Paras
    Guest

    Hi,
    I have to find the calucations of mobile radiation at gournd level just below the site.
    and the site is going to be installed on a petrol pump.

    i want to understand how much radiation will be there at ground level and what power should i radiate to avoid fire at petrol pump. (requirement of petrolium authority is the power should be less then 0.2 milli joules)

    can anyone help me on this? also would like to know if any standards are defined for this by any authority?

    #60770 Reply
    SHELDON
    Guest

    Hi Paras,

    I think you need to do a power budget. If you know the height of the tower, you can estimate the losses and hence you’ll be able to judge how much power you should radiate in order to get 0.2 millijoules at ground level. That’s basically it. I hope you understand.

    #60771 Reply
    Paras
    Guest

    Hi,
    I did the Link Budget calculations, but wants to know if different frequencies adds up the total radiation power or it will not add up.

    #60772 Reply
    Pix
    Guest

    Paras,

    The first step is to translate the 0.2 millijoules in Watts. But to do that, you need to re-read the requirements… it is 0.2 millijoules per second ?

    Then once you know the watts, you can translate that as dBm.

    Then, you can apply the free space propagation loss to 1 MS emitting at maximum power (33dBm)

    You’ll get, as an output from this formula, a distance. That is is the minimal distance between the MS and the petrol.

    If you have several MS at this distance, the power is doubled (= +3dB)

    Now for a base station, I would use the sum of each frequency emitted. Typically, one frequency is transmitted at 60dBm (that’s a very high value, but I guess you’re okay to take some margins ๐Ÿ™‚ )
    A typical BTS emits 4 frequencies in each direction. So that’s 66dBm per direction.

    But I doubt a base station could be a problem. Just being 30m above ground, I’m sure it’ll be below 0.2millijouls (per sec. ?).

    The MS is the real terror here…

    Cheers,
    pix

    #60773 Reply
    Bijoy
    Guest

    Hi Paras,Pix
    Nice discussion.
    Paras
    If you are installing a Site at petrol pump,I dont think there is any Power budgeting needed.A mobile phone does not emit the field density to create sparks on petrol pumps (I imagine the hoses have earthed shielding. The pumps are in a Faraday cage.) How could it happen?
    The maximum power that GSM mobile phones are permitted to transmit by the present standards is 2 W (although a manufacturing tolerance is allowed that makes it possible that a particular phone could transmit up to 3.65 W) . In most cases actual transmitted power will be less than this as phones have circuitry to reduce transmitted power to the level necessary for the base station to receive a clear signal in order to conserve battery power(MS & BTS PC). As mobile phones have omni-directional aerials, the maximum power that can be extracted from a mobile phone transmission decreases with distance to an extend that even 1 m away from a phone transmitting at 4W the extractable power will be much less than the 2 W threshold for a IIC gas. Hence it can be concluded that the use of mobile does not present a risk of ignition by means of the radiated energy.

    Pix
    Nice calculations though:-)

    Br\\
    Bijoy

    #60774 Reply
    Pix
    Guest

    Arrrgh, don’t dismis my beaufitul calculations so quickly ๐Ÿ™‚

    The limit is 0.2 millijoules, not 2W.

    By the way, what is flammeable is not the liquid petrol, it is the fumes. And the fumes could be “inside” the mobile station. Here, there is a risk… So MS should be forbidden around petrol.
    Wait, they are already forbidden, aren’t they ? ๐Ÿ™‚

    pix

    #60775 Reply
    AliAsgher
    Guest

    Dear Pix,

    Bijoy is talking about the power which is indeed 2W with 3.65 W max in some cases. You are talking about work done or something like this………….. (I was never good at Physics).

    Although I think 0.2 mJ is a very less value. Can you please share a link or something where you got this information from?

    Regards,

    #60776 Reply
    AliAsgher
    Guest

    *Correction

    I just re-read the post and saw the 0.2 millijoule idea.

    #60777 Reply
    Pix
    Guest

    Ali,

    0.2mJ is such a small value that you didn’t even see it in the first place ! And Bijoy didn’t neither ๐Ÿ™‚

    I must have extra-eyes… (I do have glasses… that must count)

    pix

    #60778 Reply
    paraHO
    Guest

    GSM report of 2006 refers to research that there isn’t a problem with ignition: gsmworld(dot)com/documents/health/reports/mobile_comms_fuels(dot)pdf

    But the point that PIX made about vapours in the MS, would be useful to see that research. Do you have a link for that PIX?

    #60779 Reply
    pix
    Guest

    paraHO,

    no link sorry… but that’s probably the only way the explosions in fuel stations can be explained (it was few years ago… was it real or just a hoax ?).

    pix

    #60780 Reply
    paraHO
    Guest

    Pix I spoke to a Uni professor today and his PhD was on fuel ignition and he was adamant that mobiles could not cause the spark needed to ignite vapour trapped in the MS shell.

    #60781 Reply
    paraHO
    Guest

    But he did say if a vibro-motor used brushes that a spark might be generated. I get the feeling there is a lot more to this subject that hasn’t been fully thought about.

    Cheers

    #60782 Reply
    Pix
    Guest

    ParaHO, i’ve found some interesting articles on the net:

    http://www.abc.net.au/science/articles/2006/11/30/1799366.htm

    “It is theoretically possible to set off a petrol fire with a phone. The amount of energy needed for a spark to ignite petrol vapour is 0.2 mJ, which is roughly one five-millionth of the energy stored in a fully-charged phone battery. The difficulty is that the phone is not designed to make sparks.

    The lithium battery could explode while charging if its internal regulator circuit was very faulty. But you don’t normally simultaneously charge and talk on your mobile phone while refuelling your car. The internal electronics of the phone could fail and make a spark – but the spark would be too small.

    And why worry about the phone battery when you have batteries in your iPod, CD player, mini-torch, and yes, don’t forget the big 15 kg car battery that powers the electrics of your car?”

    #60783 Reply
    Bijoy
    Guest

    Exactly Pix
    The danger is more with other gadgets rather than the MS.Not with Phase 2 MS atleast.

    Br\\
    Bijoy

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