Thursday, March 30, 2017

A Confluence of Divergent Interests - Interop ITX 2017

I'm inordinately excited to announce that I will be speaking at Interop ITX 2017 and leading two morning yoga classes this year! I couldn't be happier to combine my love of Wi-Fi and yoga at Interop.

You can find me Wednesday May 17th discussing "Wireless Security Gotchas to Avoid" and leading morning yoga classes (poolside) Wednesday and Thursday morning 7am to 8am.

You can save 20% off any Interop pass with the discount code HUBER.

See you soon at Interop at the MGM Grand in Las Vegas!

You can read more about my love of yoga over on my other blog

Comparing the Power Output

Apples & Oranges - They Don't Compare

So many 'news' sources online will compare the UV radiation of an incandescent lightbulb to the radioactive output of plutonium as if the output levels of these two things can even be indicated on the same data chart. The "radiation" power output level of the incandescent bulb is infinitesimally small when compared to legitimately dangerous radioactive particles.

I will attempt to chart the power output of devices often clumped in with one another in comparison conversations with no regard to normalizing the data in order to compare apples to apples. There are differences in spectral density measurements at different operational frequencies and I've calculated these for the common cellular networks (T-Mobile, Verizon and AT&T) based on this Wikipedia entry.

The FCC RF Exposure Guideline document doesn't get into specifics, but gives estimations for typical cellular tower sites. I used my previous blog on Smart Meters and their power output for the links for mW to W calculators, and this Field Strength Calculator tool by Compliance Engineering (a EMC testing laboratory in Australia) just to see if there was any difference in the numbers when represented in V/m
 since Lloyd Burrell of ElectricSense has the opinion that we should use V/instead of W/cm2. I found no difference in the chart data rankings using either numerical representation of the data as you can see in these charted data comparisons. The chart line shape (and the charted difference between the values) is equivalent regardless of which way the data is represented.

This document by the FCC "Questions and Answers about Biological Effects and Potential Hazards of Radiofrequency Electromagnetic Fields" is a bit dated (1999) but shows the mathematical formulas used to derive spectral density metrics for many different types of devices.

I plotted the following devices: Microwaves, Smart Meters, Indoor Wi-Fi Access Points, four common cellular frequencies used today as well as a modern DECT 6.0 cordless phone.

Here is the table version of the data I gathered:

W/cm2 V/m mW/cm2
Microwave 0.0000005 1.37 0.0005
1920–1930 MHz DECT Cordless Phones 0.0000179 8.21 0.0179
Smart Meters 0.000018 8.24 0.018
WiFi Indoor 0.000063 15.41 0.063
100-400MHz 0.0002 27.46 0.2
400MHz 0.0002 27.46 0.2
500MHz 0.00025 30.7 0.25
600MHz 0.0003 33.63 0.3
T-Mobile, Verizon, AT&T 700MHz 0.00035 36.32 0.35
800MHz 0.0004 38.83 0.4
T-Mobile, Verizon, AT&T 850MHz 0.000425 40.03 0.425
900MHz 0.00045 41.19 0.45
1000MHz 0.0005 43.42 0.5
1100MHz 0.00055 45.54 0.55
1200MHz 0.0006 47.56 0.6
1300MHz 0.00065 49.5 0.65
1400MHz 0.0007 51.37 0.7
1500MHz 0.00075 53.17 0.75
1600MHz 0.0008 54.92 0.8
T-Mobile, Verizon, AT&T 1700MHz 0.00085 56.61 0.85
1800MHz 0.0009 58.25 0.9
T-Mobile, Verizon, AT&T 1900MHz 0.00095 59.85 0.95
2000MHz 0.001 61.4 1
FCC Limits Cellular 1.6 2456.01 1600

It is difficult to read the charts when including the FCC limits on cell tower output levels as that value (1.6W/cm2) is nearly 200% higher than the average spectral density measured at cell towers operating in the 1900MHz frequency spectrum (.00095W/cm2). The chart on the left includes the FCC limit and the chart on the right shows the graph of the common "wireless" devices used as comparative items in EMF articles.

I get frustrated when I come across people on the internet claiming to be experts and in the same breath they compare a cordless phone to a microwave to a cell phone agains your head for hours at a time. Just because these things operate "wirelessly" does not mean they all pose the same threat level. This is akin to saying that a house cat is as dangerous as a lion because they're both felines.

You may have noticed that I have not focused on localized exposure to cell phone signals, meaning carrying your cell phone close to your person or having your cell phone next to your head for long periods of time spent talking on the phone. These exposure levels are represented in measures of Specific Absorption Rate (SAR). I am not a mathematician and as such, I've found no way to correlate the power output/spectral density measurements in W/cm2, mW/cm2, V/cm2 to a SAR value. Mobile phones undergo SAR testing in a laboratory environment where the phone is placed near a representation of a human head and SAR absorption rates are measured at different frequencies and positions in which the phone could be held by the user.

The audio quality of the following video is terrible, but the explanation of how SAR testing is performed is quite good.

In the years I've carried a cell phone on my person, the first 6 were only intermittent (only having the cell phone when I was on call) and I'd carry it in my handbag. Since I've had a personal phone, I occasionally carry it in my back pocket, but more often than not - it's in my handbag. When I have long conference calls, I use wired earbuds and sit the phone on my desk. My friend Sam has developed a rash/burn on his upper thigh after many years of carrying his cell phone in his front pants pocket. I do not discredit the potential harm from long term exposure to cell phone signals, but let's not start wearing space blankets! There's a big difference between a psychological ailment and a physiological ailment even if they're both physically debilitating.

If you are curious what the SAR test show for your model of cellphone, you can find this information on the manufacturer's website. Here are links to a few major makes and models.