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The argument that "many signals add up to catastrophe" is a load of bunk. 1) The RF emissions of most unintentional transmitters are next to nothing. They're d
by bradleyland 14y ago
The argument that "many signals add up to catastrophe" is a load of bunk.
1) The RF emissions of most unintentional transmitters are next to nothing. They're difficult to measure, and because signal strength decreases over distance at a rate that is similar to an inverse log, the net effect at any distance (even inches away) is even less.
2) In the atmosphere, and especially at altitude, a plane is being bombarded by cell phone signals anyway. Cell towers are designed to transmit in an elongated toroidal pattern in order to maximize efficiency, but there is still significant cellular spectrum radiation transmitted in to the atmosphere.
3) Everything else. The atmosphere is full of electromagnetic interference. You can listen to lightning strikes with an AM radio. You can also listen to the spark plugs in your car. Cosmic rays bombard the planet from outer space, despite our planets considerable electromagnetic shielding.
The bottom line is that any equipment sensitive enough to be disrupted by unintentional transmission shouldn't be used in a plane. Cell phone signals are transmitted in predictable wavelengths. Likewise for WiFi. If there were truly significant risk to the safety of aircraft at the influence of these consumer electronic devices, there would be a warning bell in the cockpit that goes off every single time RF from those bands were detected above a certain threshold. I've never seen or heard of such a thing, and it wouldn't be feasible anyway, because of the aforementioned interference already present.
- wglb 14y ago>The argument that "many signals add up to catastrophe" is a load of bunk. No, it is not. See the earlier note about Dayton. 1) RF emissions of unintentional transmitters is measured in labs all the time. Every such device, say for example, a desktop computer, has an FCC id number, certifying that it complies with a level of radiation. 2) You are completely neglecting the fact that signal strength is proportional to the inverse of the square of the distance. As the airplane is flying, the distance to cell towers is changing. The distance between the cockpit and avionics to the passenger compartment is not changing, unless the plane has broken apart. 3) Everything else: yes, but the signals from the PEDs are In The House. Lightening strikes will affect avionics.
- bradleyland 14y ago1) Exactly! The FCC requires that unintentional RF emissions must be below a certain point. That's kind of my point. 2) And you're neglecting that cell phones transmit at 0.3 watts, versus (for example) an FM radio tower that transmits at 1000 watts, or a cell tower transmitting at (around) 500 watts per channel. The point is that the radiation from cell phones is small to begin with. Ground based transmitters are far, far stronger, and planes fly nearest to them at the most critical times. 3) I don't see the significance of the distinction between the PED being 15 ft from the avionics inside the plane versus outside, but I'm open to explanations why it's significant.
- wglb 14y agoI am not sure of the power output of a cell tower--500 watts seems unreasonably large. But let's take your numbers and see where the inverse square law brings us. So multiplying power by the inverse square of the distance in feet for your cell numbers is 0.00133333. 500 watts one mile away gives 1.7935 e-5. The cell signal is 75 times stronger. And it is inside the airplane, whereas the cell tower is outside the metallic skin of the aircraft, whose attenuation effect we have not calculated. I suspect the power output of a cell tower is much less than 500 watts. With gain antennas at that frequency and line-of-sight, it is much likely to be less. Let's take a very popular FM broadcast station: WFMT. Its power is 6000 watts ERP. Its relative strength would be 6.15460 e-7. The cell signal is 2166 times as strong at the cockpit than WFMT. And that is just one cell signal.