|
Post Time: 14/01/2009 16:51:44 |
GilStevens
Total Forum Posts: 21 |
I would like someone to validate my assumptions on the FCC Standard of 1.6 W/kg used in getting a cell phone SAR value FCC ID and how to measure this with respect to our home and each person in our home.
The FCC ID SAR value threshold is 1.6 W/kg. If I use the BMI (Body Mass Index) of kg/m^2 (weight/height), then I believe if I convert in home sensor measurements (whatever they measure raw to W/m^2), I can just map BMI index values to the appropriate number corresponding to W/kg and the formula's should work. I am rusting on my algebra, and I have convinced myself it should work, but I would like someone who is more math oriented to validate my assumptions.
When I get the correct values, now I can map exposure levels to the FCC threshold value that maps to a BMI index and I can get a per person appropriate metric for exposure.
Thoughts? Math experts any comments or validation or corrections? |
|
Post Time: 15/01/2009 11:37:54 |
alasdairP
Total Forum Posts: 173 |
Hi, Gil, I really need to know a bit more about the academic level you are working at in order for me to give a properly helpful reply.
The ICNIRP SAR standard specifies a localised maximum of 2 W/kg in any 10 g of brain tissue and the FCC 1.6 W/kg in any one gramme. There are published scientific papers in the literature discussing the implications of these differences - in practice the US standard is about twice as strict as the UK/ICNIRP one.
However, for full-body SAR, averaged over 6 minutes, the UK and ICNIRP value is 0.08 W/kg because of all the issues regarding what SAR means in the first place, primarily whole body (or localised) heat load for dissipation purposes.
Body tissue varies enormously in electrical properties and you need to know the conductance, permeability and permittivity of all the various layers and where their boundaries are. You also get boundary effects when the materials have very different properties. There are many theoretical (and a few practical) papers written on SARs in various parts of the body. What you can not meaningfully do is to assume that the body is a homogeneous mass. Also, remember that the near-field and far-field interactions with tissues for microwave signals is very different.
Have a read through these - freely downloadable from the internet:
The first one is 'obsolete' but more concise that the later ones.
www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733756416
www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733817602
www.hpa.org.uk/web/HPAweb&HPAwebStandard/HPAweb_C/1195733787839
www.hse.gov.uk/research/rrpdf/rr649.pdf
Also, please note the the SAR is not an appropriate metric for the non-thermal, electro-sensitivity and microwave-sickness type neurasthenic effects that people living near to masts and DECT base units, etc, are reporting. Carrier frequency, regular pulsing frequencies and peak signal strength are much more important to these effects reported at low-power-levels.
For example, many modern communcation devices (e.g. WiFi, DECT, etc) emit very short but surprisingly high power pulses with long gaps between them that have tiny powers when averaged over time. However, they enter our nervous system as electrical signals and seem to upset many people's sense of well-being. SARs do not, and were not intended to, help protect against these sort of "signalling" or "informational" effects.
I hope this helps.
Alasdair
|
|
Post Time: 15/01/2009 19:24:52 |
GilStevens
Total Forum Posts: 21 |
Hello Alasdair,
Great post, I need to do some research. Thanks for the links.
I have seen my daughter recover from some health issues that standard Medical Doctors said they have tried everything and nothing worked and once I took care of some dirty power issues and other cell phone exposure issues, she got well within a few days. So I am a true believer there is a significant issue going on.
What I am trying to do is create a general set of metrics and mapping to the USA standard, the Switzerland standard and the most stringent, the Austria standard. In the FCC SAR tests, they only test the voice position of a cell phone to the ear. They do not test the text messaging position. I have noticed that text messaging position on some cell phones especially smart phones greatly exceeds exposure levels for each and every text message. So which teen or executive with a blackberry texts less than 6 minutes a day?
In the IEEE C95.1-2005 specification they have the normal person exposure level listed as 6 minutes at 0.08 W/kg, and the maximum threshold for anyone at 1.6 W/kg. What I am trying to do is measure cell phone voice and text messaging along with other in home measurements against the three benchmark standards, USA FCC, Switzerland, and Austria. I believe by using the BMI index I can create the map for any body size to exposure, at the macro level. I agree with you the body is not uniform with regards to absorption levels, but I don't need absolute accuracy at this time, just general overall macro reference points. The measurement tools provide a W/m^2, so I need to figure out a way to map this to W/kg, and I am thinking the BMI metric might be the best conversion tool.
I will go read the links later tonight or tomorrow. Thanks for the help.
Thx...
...Gil
gil_stevens_grs@yahoo.com
|
|
Post Time: 27/01/2009 19:22:27 |
GilStevens
Total Forum Posts: 21 |
Hello Alasdair,
Any chance you have that first NRPD document in your list? It isn't available online from the link provided.
re: Complexity => Absolutely agree, this is a very complex topic and how to map to long term effects on humans. I would say it is a statistical study of trying to limit some variables and a deep reminder on the scope of trying to measure and evaluate infinity. However the stock market can use some simple starter guidelines for what is a good value stock, good growth stock, etc. Then the complexity starts to compound as you investigate by market size, industry, and the details of the financials. I believe that we as the concerned citizens for electromagnetic waves and health effects need to find some ways to simplify the problem and measure it, and then correlate it to health issues at the macro level, that way we can provide insights for medical and RF/EMF experts to devise extremely detailed and thorough research studies to find the line of whre the problem is and isn't.
Therefore as I work through the very simplistic model of taking SAR and multiplying by BMI (Body Mass Index), at least the units map out correctly for a very rough estimate for SAR by height & weight of individual and what the home use measurement tools provide as numbers. This way the average person can read them and map to their BMI and get a very rough estimate of exposure levels. That is my thinking anyway. To have someone try to do a NRPB recommended analysis is almost impossible at home.
So in lieu of a better map, I plan to continue to use BMI times SAR to get a very rough metric for every family members exposure level. What I don't like about this measurement is that it might be crude and rough, barely ok for adults, but it certainly doesn't seem to work for unborn fetus to newborn to child to teenager. I don't know how to map that well at all. I have tried using some standard growth charts, but that just really gets me back to BMI-ish numbers. Do you have any recommendations?
Thx...
...Gil
c: 1-214-733-1946 |
|
Post Time: 27/01/2009 19:24:00 |
GilStevens
Total Forum Posts: 21 |
Hello Alasdair,
Forgot to say thanks for the NRPD links. Very good documents.
Thx...
...Gil
|
