I think any "misleading info" I quoted is trivia that is below the basic message that these products are fraudulent. The trivia doesn't materially alter the main message and indicates that even a bright but not-so-sharp technician/author in this field can get the message pretty well and publish for public benefit. I think that's more credible than a learned analysis that might prove in calculus that the Poynting vector is unchanged by as much as -240 dB at any point in space. The data seems to come from a reasonably respectable antenna company that took "available info" from a consultant's tests: a credible method. For the purpose, I think it's credible enough and documented enough if someone needs to get numbers for just how absurd and how fraudulent these products are. I can't see much value between +88dBm fraudulent and +91 dBm fraudulent, but I'm no longer a student :-) My interest was just to locate quotable references that show likelihood of fraud in these products. I found more later, but chose not to post them. If the thesis of the product is fraudulent, we don't need precise math or "paralysis by analysis" to get the message. We do need quotable references rather than just declaring ourselves "the experts" without a credible portfolio of results. I agree that the web-site author isn't the most technical person, but his purpose and audience don't need and couldn't handle rigor. I'd be amused by a Maxwell's equations field and radiation analysis, but I doubt that many others would know/care/understand/ or grade papers for it. The whole idea of the antenna boosters is like adding something inside a Faraday cage in order to boost the signal in a building: the physics of radiation and propagation is all wrong. The idea of radiation shields that do not "sufficiently" enclose the phone in E and H domains is similarly absurd as far as radiation shielding goes. The power switch is a good and "sufficient" option, however :-) Whether this 1.9GHz radiation is any kind of problem is another matter, as is how many dB of shield attenuation is enough for various parts of the spectrum. Radiation at 60Hz may be a bigger worry and much tougher to shield! :-) I don't think precision is very useful for these two products: our main point should be to provide public info to educate the masses to the very basic ideas of fraud vs not fraud. Having multiple clear citations may be more important than having stuffy and erudite ones that common folk cannot follow. YMMV. I think you're missing the forest for the trees on this. Opinions are great, but... as you lecture us, keep in mind that some of us here have already graduated and have a few years of experience with RF - and Maxwell's equations. :-) Regards, Chuck > -----Original Message----- > From: mgenelin at ieee.umn.edu [mailto:mgenelin at ieee.umn.edu] > > Hey Chuck- > > The first of the two sources that you have linked below seems > to contain > misleading, inaccurate information. My first tip as an RF Engineering > Student was the claim that you can "increase the effiency of your > antenna". They claim that "The increase gain can be from 3dB (100% > increase in signal strength) to 9dB (400% increase)." > > The first part of this statement is accurate: 3dB increase in signal > strength, in general, is *about* double the gain. (3dB = 10 * > Log10(1.99526) and 1.99526 is about 2, or twice the gain.) The second > part, however, is inaccurate. 9dB = 10* Log10(7.94328) or > about a gain of > 8, not 400% or 4. This means that a one-watt signal would > effectively be 8 > watts, not 4 watts. This means that our friend mis-calculated > something or > didn't get his calculator out at all when creating the web page. > > Perhaps the most tell-tale sign that something is amiss when > I am reading > web sites on the internet is when I see statements like: > > "Without getting into the physics of why it does not work,..." > > Whether the device does or does not work doesn't seem more > apparent then > the accusations on the web page, and the tests done by the > author seem to > lack any technical detail. > > The second link is interesting, as it comes from the Federal Trade > Comission. I always looked to the FTC for consumer advice on products, > until now. The FTC claims that: > > "According to the FTC, there is no scientific proof that the so-called > shields significantly reduce exposure from electromagnetic emissions." > > Perhaps this is true, given the current-day consumer-sold RF > shields. But > that is not to say that we can't create RF shields. The real > problem is > that consumers want small size, and don't want ugly antennas > getting in > their way of cell phone usage. > > Do cell-phones cause cancer? Dr. Dean-Edell last night on the radio > dispelled this common belief. There is no scientific evidence > either way. > Perhaps my RF engineering professor put it best: > > In the early days of cell phones in Europe, heavy users of early 1 and > 5-watt cellphones complained of getting headaches after using > the phones > for an extended period of time. After some experimentation by the > goverment, Europe set it's limit at 1 Watt for hand-held phones with > radiators next to your head. In the USA, the FCC set that limit at .5 > watts. As a result, most of your cellphones radiate 450 mW = > .450 Watts. > > The FCC also sets the safe RF exposure limits for humans. > According to the > assignment that we recently handed in, located at: > > http://www.ece.umn.edu/class/ee4601/4601F02Ass3.pdf > > (see problem 3) The FCC says the safe exposure limits at 2.2 Ghz in a > 24-hour period are 2mW/cm^2. Let's take my cellphone, a > voicestream phone, > for example: > > I have a 1.9 Ghz phone, like most other digital phones. The Professor > estimated that about 1/3 of the power from the cellphone is > disappeated > into my head as I use it. That's 450 mW /3 = 150 mW. The antenna on my > phone spans the entire length of the phone casing, but I will discount > that for now and only talk about the external antenna. The external > antenna is 3cm tall by about 1 cm wide. This is 3cm*1cm = 3cm^2. > > Roughly, I am disappating 150mW/3cm^2 or 50mW/cm^2 into my > head. If I can > assume that the FCC's guidelines for 2.2 Ghz are close to > that of 1.9 Ghz > (since they are close in frequency) then I have exceeded the 2mW/cm^2 > exposure limit if I use my cellphone for a 24-hour period. > > But then again, the batteries on my cellphone only last 2 > hours max. So, I > am exposed to 50mW/cm^2 of power for 2 hours, where the safe limit is > based on a 24-hour period. If I only use my phone 2 hours a > day before the > battery dies I believe I will come just above the daily exposure > guideline. > > I apologise now for getting all technical and stuff here, but > I have seen > some things go by on the list as of recent that are > completely off-base > and I haven't had time to reply to all of them until now. > > Regards, > ---Matthew Genelin--- > > > > > Jeff asked where I saw these notices, so I thought others > might enjoy > the references... > > > > Fraudulent cell phone antenna boosters described here: > > http://cellantenna.com/internal_cell_phone_antenna.htm > > > > also sold with similarly fraudulent "radiation shields": > > http://www.ftc.gov/bcp/conline/pubs/alerts/cellshlds.htm > > > > I'm not sure that the ad I saw for lead-lined jeans was a > joke... might > have been a product for sale! Be careful! The power output of a > typical wireless card or cell phone is much more than a > million times the > natural radiation around "sensitive parts", so maybe TCWUG should make > some public service announcements... > > > > > > > > --- > > Chuck