Does installing cell towers on hospital roofs, have any effect on equipment inside the hospital? Also, how come cellphones are not allowed in hositals?
This is a total mess where some facts but mostly a lot of superstition and pure feudalism are at play.
DECT phones, which we know are just as agressive as any cell phone, are used heavily by hospital employees. Diathermic devices that emit in a very broad frequency range and frequency inverters that act as very powerful RF emitters are used in hospitals. But a measly cell phone can't even be taken inside the building.
Same thing with airplanes. They are subject to powerful radar beams. Sometimes actualy being a hazard to crew and passangers, but seemingly not a problem for the technical equipment on board. And micro-wave ovens are used on board to heat that stuff we are supposed to eat during flight.
I once asked the Air Transportation Authorities why cell phones couldn't be used on airplanes. The answer I got is: "It is because the ground stations get confused if more than one station can see the same phone. The roaming won't work". I have this answer in black and white, on paper.
I asked again if it wasn't because of risk for interference with the navigagtion equipment. "No. That is not the reason".
I now hear that IATA is thinking about letting us use our loved phones onboard airplanes. But nothing decided yet. Same thing will probably happen in hospitals. The whole thing is a mess. And an Urban Myth.
The ONLY time cellphones are not allowed to be used is during take-off and landing.
As 9/11 demonstrated, cell operation in low flying aircraft has no problems with respect to cell coverage. Any time a cell phone crosses a cell boundary, the cell towers have little problem with resolving what to do with the signals.
I hardly think that the airlines are really that concerned about our ability to not have problems with our cell phone bills.
Moreover, the restriction against electronic devices also apply to laptops and PDAs, which do not have cell phone-related issues.
We (European airlines) are not allowed to use cell phones on aircrafts. Not under any circumstances. It is only "when the plane has come to a complete standstill" at the gate that we are allowed to switch on the phones.
Other electronic equipment (computers and so on) is allowed during flight. But not during take off and landing.
Voice recorders are not allowed - they contain an oscillator for erasure and tape "priming" and oscillators are not allowed (thought of as transmitters, even if extremely low power and low frequency), not even the local oscillator in a radio receiver. You can't win a discussion with security people. So better do as told. Grudgingly.
I am curious about my new Nokia 9500. It is a phone with a PDA. It has a "Phone Off" mode. So I can use the computer during flight. I wonder if I will have problems with that. I guess I will.. I always have problems.
The witch processes continue. But now on a technical plane.
The only issue I've had with cell phones being on during a flight is that the battery gets clobbered; I think because it's constantly searching for a cell to link with.
The real issue is not whether cell phones ACTUALLY cause interference, but whether they MIGHT cause interference. I think we can all agree that it would be foolhardy to take that risk with a plane loaded with passengers.
Obviously, one could perform tests, but since cell phones and laptops have a half-life of about 1 yr, testing would have to be nearly continuously ongoing just to keep up with all the new models that are introduced. Likewise, aircraft avionics have started to use COTS devices with limited or unknown performance in the presence of EMI.
Additionally, both cell phones and laptops have increasing functionality and clock speed, which would be another potential EMI issue.
But I do not agree. About COTS; they are surely tested to meet flight requirements. And my own COTS are not at all sensitive to cell phones. I have tried to upset several computers (yes, opened them and made my phone and other's transmit continuously while moving around inside the running computer) but never managed to have any reaction.
I guess that it valid to say that equipment that is more in the "far field" should be even less prone to being disturbed by a phone.
Same goes for COTS like PLCs and VFDs. The only problem I have had with cell phones is with old analog equipment when using the phone in front of an open cabinet. Doors closed - no problem.
I can state for a fact that at least some cell phones mess with equipment. I've got a newer Motorola cell phone and have noticed it causes computer monitors to act glichy, same thing when the phone is around radios, but you can hear the glichy-ness through the speaker. Also causes interference through the VFR radio in the Cessna 172 I've been training in.
From what I understand, cell phones in aircraft DO cause confusion on the ground, and I have experienced the result. All I have to do is leave my phone on when I visit one of my mountaintop television transmitters. If the cell system sees my signal at an equal level at several sites (which can happen easily from the altitude where these transmitters are) the system cannot figure out which site I should belong to. However, there is a much worse problem. Because the voice channels are re-used from one site to the next, my phone could work well with one site, while simultraneously jamming the voice channel of someone else who has the misfortune of using the same voice channel as my phone was assigned by the site that accepted my phone and allowed me to talk.
The way cell systems handle this is to label such a phone a "rogue." Once your phone has been designated as a "rogue", your phone will not work again until you power cycle it. I have had this happen several times, and at first, I thought there actually was something wrong with my phone. It took a cell site engineer to explain to me that by coming into several sites at the same level, the cell system put my phone into the "doghouse" to protect other users from interference.
As the population of cell phones increases, cells must get smaller and smaller, and their number increase to meet the demand, because each cell has a limited number of voice channels, and once they are all in use, no more calls can be handled by that site until someone ends a call. People do not like not being able to talk at will, so all of the cell carriers are busy making their cells smaller and building more of them. That reduces the amount of RF coming from any one cell because the distances involved are getting shorter and shorter.
About cell phones in aircraft; the cell companies have decided that they have been losing a lot of business from people in aircraft, so they are now partnering with the airlines, and are starting to build "mini" cell sites inside those commercial airliners. This serves several purposes, but the most significant is that the cell site in the plane can tell every phone there to use a minimim of transmitting power, which will prolong the battery life of all of the phones in the plane, and it wil prevent interference from the phones in the plane to cell sites on the ground. In addition, the cell site in the plane itself runs a very low power (about 1 milliwatt) with a "leaky cable" antenna in the ceiling of the plane, so it also will not cause problems on the ground, even if the plane is near landing or has just taken off.
I wouldn't worry much about a cell site causing RF interference to equipment in the hospital because I'm sure a lot of EMI/EMC testing was done before any cell company was allowed to build a site on any hospital roof. What hospital administator wants to be sued for a wrongful death caused by an electromagnetic compatibility problem traceable to the cell site on the hospital's roof?
That supports what the ATA said about confusing ground stations. Having a leaky cable inside the aircraft to keep transmitter power down sounds perfectly logical and seems to be a good solution.
The original question about cell phones in hospitals remains: Is the cell phone ban in hospitals founded on physical realities or on fear and superstition? And, what about cell phone towers on hospital roofs?
I have designed cell phones for the last 3 years, and the reason that you cannot use cell phones on planes is due to potential RF interference with the aircrafts electronics, period. Cell phones can put out ~21-24dBm of power, and COULD couple into the electronic circuitry. The frequency ranges from 900 - 2100MHz. Therefore, to be safe, they do not allow you to use them on the plane. Also, your phone is almost always seen my multiple cell sites / basestations at the same time.
skogsgurra,
With regards to your Nokia 9500, as long as you are in "Phone Off mode", or "Airplane mode" (Motorola's equivalent mode for A/M1000), there will be no problem using that device while in flight. That mode simply disables the RF section of the phone (both reciever and transmitter). Therefore, it is like using a normal laptop.
Note: The reason that laptops are not a problem is simply due to the amount of transmitted power. While clock frequencies are 2.1Ghz (or 2100MHz, same as WCDMA), the amount of energy that is getting transmitted from from a computer is signifigantly less than that of a cell phone.
TransmitterTamer has the right answear.
Especially for CDMA transmissions that depend on
uniform incoming power to help the tower seperate
the channels.
Com'on guys! It doesn't matter whether it is interference or not why they don't want you to use your cell phones when the plane is taking off or landing.
If we can avoid using our cell phones just for a FEW MINUTES, not an hour or a day, for the safety of all passengers including your beloved self why NOT?
This is already common sense (which I believe not common to all!). Can't we exist in this world without using our cell phone just for a short time? We use it even if we walk, we drive, we eat, etc. etc. and so we can't focus on doing one task and accidents can happen.
Being an engineer is not just knowing the technical side of life thus becoming so technical that we fail to consider what is more practical.
It is a well known fact that cell phones generate enough RF radiation to interfere with the transmission of model aircraft radio control equipment. Most model flying fields enforce a rule that cell phones must be turned off and left in your vehicle.
It is better to slightly inconvenience a few passengers than risk a major aviation disaster because of some person using a cell phone.
That was my contention here! If you think it may interfere, then don't take the risk. Just put off the cell phone and do something else while on flight.
Or better still use your cell phone a lot prior to boarding so, you can rest while on flight. A lot of people I know, chat a lot. If you try to analyze much of their chats are nonsense. If it were with sense, it wouldn't be that long, because the brain can process only limited sensible conversation.
My conclusion to this is, irrespective of whether it can directly interfere the signals or not, the stake is too high to do it, so for everybody's sake refrain from using it just for that period unless extreme emergencies.
