cell phone jammer - nonsense?

[fuelevaporator]

most companies do not allow use of cell phones but fight a lost battle since after "cabin secured" passengers still use them during most critical phase of flight when only action of cabin crew can be "please switch off...".

many times I thought we either should give up completely on this one or use jammers but of cours these would disturb even more...

since passenger planes transported cell phone controlled bombs I ask myself even more about use of jammers - maybe they could even be certified for use in planes.

what do you think - maybe you have an idea whether "harmless jammers" are technically possible or not...

[grounded27]

No technology is harmless...

[ion_berkley]

I can see absolutely no reason why a cell phone "jammer" could not be designed and qualified into service on board an aircraft, the fundamental issue with the reluctance to have cell phones on board in the name of "safety" is that they are not a part of the tested and integrated systems of the aircraft. Sources of strong RF radiation on aircraft are of course common place in the form of radios and radars. "Jamming" it's self is however is a complex subject, whilst it might be tempting to just imagine simplistically generating a strong "noise" signal of the same frequency range that the cell phone works at, there are other much more interesting approaches, some of which are obviously rather sensitive. A good example being the actual cellular base stations now being used in a few aircraft trials. These actually "jam" the active phones on-board from talking to ground based stations (and hence dramatically reducing their potential EMI effects) by causing their transmit power to be turned down to a fraction of there maximum possible setting.

Thinking more laterally other approaches might be easier to achieve your desired effect. The aircraft hull has already got great potential to be a very effective Faraday cage that prevents RF signals passing through...removing windows or giving them a conductive covering, making sure all hull sections are grounded together etc. Also it is very simplistic to find an active cell phone since it constantly transmits at regular intervals.

But at the end of the day its the same story as always, vast efforts get focused on countering a very focused and narrow vector of attack because it's the media cause of the day, and a 1000 other equally effective simplistic approaches remain and you can't practically counter them all. The real solutions to reducing terrorism are not technological nor militaristic I suspect.

[Agaricus bisporus]

Just do a search for "cell phone jammer", They're readily available tho sadly not in UK, every commuter train should have one!

But just apply a mite of common sense here for God's sake. If you're concerned about radhaz from a mobile phone why would you swamp the area with the same stuff, but continuously and in sufficient strength to blot out the little mobile?
Preventing a neighbour's noise nuisance is not achieved by building a concert PA system in your garden, is it?

D'oh!

One of three things is required.

1)Pax are physically prevented from using mobiles on aircraft - ie removal/ban on board, and draconian punishments. (no balls) We've all but stopped drunks, we could do it.

2)Manufacturers design aircraft immune to cellphone interference. (vast expense, decades of lead-time)

3)Give up and just let it happen/continue pretending to discourage it, until an accident occurs.

I think we all know which won't happen, and which will. We'll just have to live with it as we haven't the courage to stop it.

[mm43]

A low power multi-band cell jammer in each cargo hold of pax a/c and probably throughout freighters would certainly inhibit the remote triggering of any device that made its way onboard.

The FAA in reviewing special conditions under 14 CFR Part 25 of the High Intensity Radio Frequency interference requirements for FBW aircraft such as the A330 have set some high standards. The HIRF requirements can be found within this FAA publication (http://www1.airweb.faa.gov/Regulatory_and_Guidance_Library/rgSC.nsf/0/98A7EAF7BEE427EF86256FA900660633?OpenDocument), and an excerpt is reproduced below:-

The Airbus A330 airplanes will utilize electrical and electronic systems which perform critical functions. These systems include the electronic displays, integrated avionics computer, electronic engine controls, engine over-speed/over-temperature protection, etc. The existing airworthiness regulations do not contain adequate or appropriate safety standards for the protection from the effects of HIRF which are external to the airplane.

Airplane designs which utilize metal skins and mechanical command and control means have traditionally been shown to be immune from the effects of HIRF energy from ground-based and airborne transmitters. With the trend toward increased power levels from these sources, plus the advent of space and satellite communications, the immunity of the airplane to HIRF energy must be established. No universally accepted guidance to define the maximum energy level in which civilian airplane system installations must be capable of operating safely has been established.

For the purposes of this special condition, the following definition applies:

Critical Functions: Functions whose failure would contribute to or cause a failure condition that would prevent the continued safe flight and landing of the airplane.

At this time the FAA and other airworthiness authorities are unable to precisely define or control the HIRF energy level to which the airplane will be exposed in service. Therefore, the FAA hereby defines two acceptable interim methods for complying with the requirement for protection of systems that perform critical functions.

(1) The applicant may demonstrate that the critical systems, as installed in the airplane, are protected from the external HIRF threat environment defined in the following table:

http://i51.tinypic.com/31323c4.jpg

or,

(2) The applicant may demonstrate by a laboratory test that the critical system elements and their associated wiring harnesses can withstand a peak electromagnetic field strength of 100 volts per meter without the benefit of airplane structural shielding, in the frequency range of 10 KHz to 18 GHz.The use of this type of jamming would soon be circumvented, i.e. other means would be found to trigger such devices (or similar) on demand.

mm43

[catiamonkey]

The question is what you're trying to accomplish. If you're trying to prevent people from calling in planes, the cell phone network does a pretty good job of jamming itself.

The plane will be fine from the jammer. For 900 MHz, 935 V/m=2.3 kW/m^2=231 mW/cm^2. That's 231 times the safety limit of 1 mW/cm^2. The RF concern with cell phones in planes isn't the 900 MHz emissions, but the harmonics that leak out into the HF and VHF comm ranges. That's the same reason why you can't use a broadcast radio receiver in planes.