What is the deal with electronics and radios on airplanes?

Follow-up comment with regards to use of cell phones. The phone companies has not figured yet how to select roaming charges from different providers once cell phones are used @ 35K Ft. or so...And I agree also that its rude to be using cell phones and talking in flight. In Japan, its rude to use cell phones in public transport vehicles, planes ,trains, buses etc..

I think the main reason is safety. Takeoff, climb, approach and landing are the most critical stages of flight. They want all pax attentive and ready to go whenever an emergency situation arises. Notice that after touch down you can turn them on since its just between taxiway and the gate that left to travel. I tried using a handheld VHF-UHF radio to once listen to pilots-controller conversations and nothing happened.

You can conduct a little experiment. Turn on a pocket AM-FM radio and put your cellphone (not on call mind you) nearby. You will be surprised.

I was on a flight this weekend and they now ask that you not turn on any cell phone even if it has an airplane mode.

There are (2) principles the airlines are working to: a) Almost all active electronic devices emit stray signals at some level - ask any ham who's using, or tried to use the shortwave bands. There's all sorts of interference from computers, monitors, TVs, Cable services, etc., and (worst of all) BPL. The potential for interfering signals, with a plane full of people with electronic devices, would be very large.
b) The airline personnel have no easy way to screen out the bad (interference-causing) devices, from the good ones. Banning them all is the easy / safe way out.
Yes, the airplane avionics are designed to withstand quite a bit - but this is relative to outside sources - e.g. flying through the near field of a TV transmitter, or a weather radar.

Usually, the highest probability of mishap in an airplane are during takeoff and landing. It is reasonable to expect electronic devices to be stowed away during this time to keep them from flying around, or to keep people from tripping over them in an emergency.

Combine this with a tubular metal waveguide leading to the flight controls. This is why devices containing radios are not allowed to be operated on planes. Granted, this was more of a problem in the past, when radios had a lot more analog components for tuning and were not as well shielded. Non-radio computing devices are allowed, but only at high altitude, to give the pilot time to regain control of the plane in case something unexpected happens. (Broken into multiple pieces because the anti-spam filter doesn't accept a term for the room where the pilot sits)

The emission can be on the same frequencies used by voice communication and navigation, jamming the electronics.

Filtering then eliminates the unwanted bandwidth. However, the superhet frequency itself can leak out of the device, as well as frequency-shifted copies of other signals detected by the antenna but not necessary used by the device.

I thought the reason had to do with superheterodyne tuners, which most radios and TVs use for tuning. The superheterodyne tunes by mixing the signal from the antenna with an internally generated frequency, resulting in frequency offset copies of the signal at +/- the superhet frequency.

Non tranmitting digital devices are classified by the FCC as unintentional radiators.

Do a search for \”Chris van Rossman\’s TV\” and add in \”New York Times\” and you will see the consequences of what an unintentional raditor can do. Corvalis Oregon in 2004.

I think in the case of cell phones there maybe the issue of signals accessing and changing access to several cell towers which may cause trouble with the phone services.

Any alternating current flowing in conductor is actually a transmitter. Usually a low level one, but those add up when you have lots of those. If you wonder about electronics that are installed in planes, like seat back televisions, they can measure how much of interference they are and shield them better if that is a problem. Those intended or non-intended transmitters might interfere with mostly the radio traffic between plane and ground. And that could be a safety issue.

There are little transmitters in electronic devices calls oscillators. The put out very small signals which are intended to be used only by the device itself. In theory, a defective oscillator could transmit a signal on a frequency which conflicts with the electronics on the plane. The FAA isn\’t in the business of certifying every device a person could carry.

Do you really want to listen to 100 strangers cell phone conversations while on a 3 hour flight?

They should be banned on flights out of common courtesy. We got by for years without these items in our planes and cars. People expect everything right now theses days. We are a spoiled, ungrateful species.