Hi Adam,

On Thu, Oct 1, 2009 at 10:21 AM, M. Adam Davis <stienman@gmail.com> wrote:
> Radiation affects biological material.  That is to say that biological
> material reacts or acts/grows/etc differently in a radio field than
> otherwise.

While I certainly would not declare RF exposure to be safe, I have
never heard of any definitively proven effects of RF on living tissue
beyond heating effects. Do you have information otherwise?

>
> However, minor magnetic fields of short duration appear to leave no
> lasting change. =A0While under the influence of a field there is a
> difference, but everything goes back to normal except in the case of
> overexposure.

I'm not sure why you make reference to magnetic fields here
specifically. Are you talking about DC or low-frequency magnetic
fields? At cell phone frequencies, there are going to be both electric
and magnetic fields present in roughly comparable magnitude quite
close to the antenna (i.e., the far field is not very far out)


> Further, the radiation decreases exponentially by distance, so at one
> meter there is no known biological affect for standard cell phones
> signals.

Actually, it is not quite exponential. Very close to the antenna
(i.e., less than 1 wavelength) it may not decrease very much with
distance at all. Between 1 and 10 wavelengths, it drops very fast
(i.e., dipole field rather than a plane wave, roughly 1/r^6 for power,
or 1/r^3 for field strength). Beyond 10 wavelengths, the power per
area drops as 1/r^2 and the field strength drops by 1/r.

>
> Lastly, the transmitter in the phone is very, very, very weak - we're
> talking mW, not watts of transmitting power.

Are you sure about this? Given how warm the phone gets during a call,
as well as the distance it must cover reliably, I'd guess that the
peak power is about 1 or 2W and the average at least a few 100 mW.

>
> On the other hand, this is a pretty good reason to text instead of
> call - the transmission burst is very small and short, and it's away
> from the head.

Interesting advice. I do not have a regular phone - only a cell phone.
Therefore, I am particularly concerned about this. My strategy, since
neither I nor most other people I call are big into texting, is to use
headsets and get the phone away from my head, usually on the desk in
front of me. I have found, though, that many headsets do not work all
that well. I tried several wired headsets first and they had strange
quirks like my phone sometimes deciding to mute the microphone of the
headset for no apparent reason. So, I now use a Bluetooth earpiece -
of course that itself is RF but much lower power.

Sean

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