cornutt@freedom.msfc.nasa.gov (David Cornutt) (04/02/91)
There's one hell of an argument going on in the Usenet rec.aviation group about the use of cellular phones from aircraft. Can anyone answer: (1) what effects this could have on the cellular phone net? (2) what, if any, FCC regulations might apply? David Cornutt, New Technology Inc., Huntsville, AL (205) 461-6457 (cornutt@freedom.msfc.nasa.gov; some insane route applies) "The opinions expressed herein are not necessarily those of my employer, not necessarily mine, and probably not necessary."
David Lemson <lemson@ux1.cso.uiuc.edu> (04/04/91)
cornutt@freedom.msfc.nasa.gov (David Cornutt) writes: > group about the use of cellular phones from aircraft. Can anyone > answer: > (1) what effects this could have on the cellular phone net? We've been through this before. The bottom line, from several authoritative sources that I'm told, is: In rural areas where cells are likely to be fairly spread apart, the impact on the cellular network is likely to be minimal. It might be even "ok". (If you can even get a tower!! The antennas that cell phones use, including on the site towers, have almost zero coverage straight up, where you are!) In metro areas, such as if you were in a heli over Manhattan, it would WREAK HAVOC, as it keeps bouncing you from channel to channel trying to only receive you at one site, which it receives you at several sites at once! This is discounting the fact that you might hear others' conversations. As for FCC rules, it appears that there are no regulations that disallow this, but it is REALLY not a good idea. Cell phones were made for people to be travelling relatively slowly. David Lemson U of Illinois Computing Services Student Consultant Internet : lemson@ux1.cso.uiuc.edu UUCP :...!uiucuxc!uiucux1!lemson
sbrack@iuvax.cs.indiana.edu> (05/09/91)
reb@ingres.com (Phydeaux) writes: > Hi! During a recent flight, I had my phone turned on and noticed the > 'roam' light was on. I tried to place a call but it didn't go > through. We were at about 39,000 feet, and I didn't expect it to. It > would stay on 'roam' for a few seconds and then go to 'NoSvc'. But, > when we were down to about 15,000 feet I noticed the 'roam' light was > on continuously. I tried to dial again and it worked like a charm. I > was using a .6 watt Motorola "Ultra Classic" portable with the small > (1/8 wave?) antenna, and I wasn't even in a window seat! When you activate a cellular phone that high above the ground, its transmission power is so high over such as great surface area, that you end up blanking cells over large (> 2-3 states) land areas. This can result in interruption of service. It is taken **very** seriously by the FCC and the FAA, and probably the carrier who lost revenue due to your "experiment." Pilots can lose their liscenses for allowing these devices to be used on their aircraft. > [Moderator's Note: You should have tried a few more tests of things > you're 'not supposed to do', such as *711 to ask what carrier it was, > and 0 for the operator to find out what place was getting your call. PAT] The footprint of the cellular signalcould have stretched over several states. Presumably, he could get responses from several cellular systems simultaneously, depending on the complexity of his phone. (Some automatically lock on to one signal, others are more "open." Steven S. Brack | I don't speak for OSU. InterNet: Steven.S.Brack@osu.edu | (Bill Miller just can't BitNet: Steven.S.Brack%osu.edu@ohstvmsa.bitnet| understand that.)
Floyd Davidson <floyd@ims.alaska.edu> (05/17/91)
In article <telecom11.365.1@eecs.nwu.edu> "Steven S. Brack" <bluemoon!sbrack@cis.ohio-state.edu> writes: > steves@aerobat.labs.tek.com (Steve Shellans) writes: >> In article <telecom11.332.3@eecs.nwu.edu> reb@ingres.com (Phydeaux) >> writes: > [Talks about activating his cellphone in an aircraft] >>> I realize that you're "not supposed to" do things like this, but if >>> anything had happened I could always have called 911 ;-)> >> I don't think this is funny. The reason you're not supposed to do >> things like this is that stray signals from transmitters and other >> kinds of electronic equipment can interfere with the navigation >> instruments. > While using a cellphone in an aircraft is not a good idea (it, > in fact, has the potential of denying cellular service to users over a > multi-state area), aircraft navigation equipment is really very hardy. > The frequency and power put out by a cellphone shouldn't have an > appreciable effect on airline equipment. It may, however interfere > with the equipment used in general aviation aircraft. I'm not a pilot, I'm a technician who lives in the state with the highest ratio of airplanes to people. I fly a LOT. I talk to pilots at LOT. I talk to FAA people too much. If a pilot allowed you to use a cellphone on an IFR flight that I was on, I want off the plane, NOW. If I saw you using one I would immediately make the pilot aware of it. I don't think it is funny AT ALL. I also don't see what difference it makes if the plane is a commercial airliner or a general aviation craft. The radio's and the navigation systems are the same. (Some day I'll tell you how I learned that Loran C can be 60 degrees off. No problem, just makes the pilot eyes get large when he breaks out of the clouds ...) >> [Moderator's Note: I did not think it was funny either ... maybe next >> time he decides to flex the rules a little in his experiments he will >> try the one which says 'keep all radios, including cell phones, turned >> off in areas where dynamite and other explosive powders are being >> used.' If anything goes wrong, someone will always call 911 :( PAT] > In all seriousness: can a cellphone trigger explosives? It > seems that a radiodetonator would need to be very selective about what > signals trigger it. Yes it can. A radio detonator probably would be very selective. How about just regular blasting caps with a few hundred feet wire (an antenna). Or even just a couple feet of wire (a half wave at VHF frequencies). Someone will call 911, and as Pat implies, it won't be on THAT phone! Floyd L. Davidson | Alascom, Inc. pays me, |UA Fairbanks Institute of Marine floyd@ims.alaska.edu| but not for opinions. |Science suffers me as a guest.
James Turner <turner@newkirk.hq.ileaf.com> (05/17/91)
I don't know if anyone has actually posted the FAR (Federal Air Regulation) that applies to this kind of stuff, but I thought I'd give you the verbatim text: FAR Part 91 (General Operating and Flight Rules) 91.21 Portable Electronic Devices (a) Except as provided for in paragraph (b) of this section, no person may operate, nor may any operator or pilot in command of an aircraft allow the operation of, any portable electronic device on any of the following U.S.-registered civil aircraft: (1) Aircraft operated by a holder of an air carrier operating certificate or an operating certificate; or (2) Any other aircraft while it is operating under IFR. (b) Paragraph (a) of this section does not apply to - (1) Portable voice recorders; (2) Hearing aids; (3) Heart pacemakers; (4) Electric shavers; or (5) Any other protable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communications system of the aircraft on which itis to be used. (c) In the case of an aircraft operated by a holder of an air carrier operating certificate or an operating certificate, the determination requried by paragraph (b)(5) of this section shall be made by that operator of the aircraft on which the particular device is to be used. In the case of any other aircraft, the determination may be made by the pilot in command or other operator of the aircraft. COMMENTS AND EXPLANATIONS: (a) - Not that these regs are binding over US-registered planes only. What you do on a British Airways flight from JFK is between you and them. (1) This is basically any commerical air carrier. (2) This is anyone flying under instrument conditions (poor visibility). This means any pilot in any aircraft, not just commercial. (b)(5) Note that the person making the decision must determine that the device WILL NOT interfere. This is different from prohibiting devices that WILL interfere. Basically, if you're not sure, you can't permit it. (c) Also note that the Pilot in Command (Captain) of a commercial flight is not allowed to make this determination. It must be made by the owner (read lawyers). Hope this will help clarify things. James M. Turner | > (LET ((DISCLAIMER 'INTERLEAF-NOT-RESPONSIBLE)) Senior System Engineer Interleaf, Inc
"Patton M. Turner" <pturner@eng.auburn.edu> (05/17/91)
> In all seriousness: can a cellphone trigger explosives? It > seems that a radiodetonator would need to be very selective about what > signals trigger it. Under proper conditions, blasting caps can be set off by an RF field. A few years ago, while installing a fiber link between two CO's near here I had some caps left over after we blasted a trench through rock on a section of highway right-of-way. Being the curious sort, I decided to see if I could set a cap off with a CB or VHF radio. I cut one leg of the wire to a resonant length (about 50 feet, slightly higher for the CB), and grounded the other leg to a ground rod. Using a 2 meter amateur transmitter feeding 150 watts in to a 5/8 wave (3db gain) antenna, the cap exploded from a distance of 20 feet (this was probably overkill). The CB did not set the cap off at a distance of 7 feet. Note: I buried the cap in the ground, I'm not stupid. There are several reason that caps are almost never set off accidentally. First, lead wires are NEVER allowed to be grounded, and splices are not even allowed to touch the ground. Secondly, the shooting line (wire from caps to blasting machine) is twisted together to prevent an induced potential between the wires. Finally, the end of the shooting line is shunted until it is attached to the blasting machine, then the blasting machine will shunt the line until the fire switches are depressed. In conclusion, I believe it would be virtually impossable to detonate a blasting cap with a cell phone. But just to be safe ... Pat Turner KB4GRZ internet: pturner@eng.auburn.edu
Scott Dorsey <kludge@grissom.larc.nasa.gov> (05/17/91)
In article <telecom11.365.1@eecs.nwu.edu> bluemoon!sbrack@cis.ohio-state.edu (Steven S. Brack) writes: > In all seriousness: can a cellphone trigger explosives? It > seems that a radiodetonator would need to be very selective about what > signals trigger it. The problem here isn't radiodetonators, but ordinary blasting caps. Because being near the scene of an explosion is a bad thing, several hundred feet of wire are often run from the detonator to the cap, enough wire to act as a reasonable antenna. It's possible that a local transmitter will get enough current induced in the leads to fire off the cap; I know that nearby 4W 27MHz CB rigs will do it. I rather doubt that anything at significantly higher frequencies and lower power would do any damage, but I do not want to be the one to find out. scott
u1906ad@unx.ucc.okstate.edu (05/17/91)
Recently somebody was wondering about the warning signs seen around
areas where explosives are being used, advising people to turn off
their cellular phones and two-way radios. While I am not an
explosives expert, I can comment on the reason for this prohibition.
Some of you have probably had the unpleasant experience of
hearing a CB or other type of radio transmission over something that
wasn't supposed to be a radio such as a stereo amplifier or telephone.
This happens because the radio frequency signal is changed from
alternating current to direct current by solid-state components in the
system getting the interference. The DC signal is an extra voltage
introduced randomly into the system which can have unpredictable
results.
In an amplifier, it causes noise or actual audio to be heard. In a
computer system, it may scramble data and cause a system crash. While
the detonators used on a construction site, for example, may not be
radio controlled, the wire leading to them can act as an antenna. A
nearby radio transmitter might just develop enough current in the wire
to trigger the detonator.
Finally, mobile phones and frequency-trunked radios should probably be
turned clear off because they can automatically transmit as a result
of a command from the controlling system such as the answer to a ping.
When considering the things that could go wrong, the expression
"safety first" really applies.
Martin McCormick amateur radio WB5AGZ Oklahoma State University
Computer Center Data Communications Group Stillwater, OKmike spann <mikes@gammafax.gammalink.com> (05/18/91)
In article <telecom11.365.1@eecs.nwu.edu> bluemoon!sbrack@cis.ohio- state.edu (Steven S. Brack) writes: > In all seriousness: can a cellphone trigger explosives? It > seems that a radiodetonator would need to be very selective > about what signals trigger it. > [Moderator's Note: They are very selective about signals, however a > very close radio signal often times can overwhelm receivers in the > area, overloading them with the signal from the nearby unit. I've > never heard of a cell phone (or any radio) causing an explosion like > this, but I guess it is possible. PAT] Digging way back into my memory, I do remember a story (maybe even true) where police officers were told not to dump their spare bullets into the same bag as their hand held radios. The story I was told was that should the push-to-talk button be pressed, the electro-magnetic waves could cause a round to go off. When pressed to explain, their technical expert said that the oxides between the primer and the case could act as a rectifier at 150 MHz, and convert some of the five watts of radio energy into a DC voltage. Supposedly, this DC voltage could set off the primer and therefore the bullet. I thought this was a flimsy excuse, but it seemed to be accepted by all the experts who were trying to figure out why some cop accidently shot himself. I am not sure what this has to do with Telecom other than side effects of seemingly harmless acts are often difficult to fully comprehend. Michael Spann mikes@gammalink.com Voice: +1-408-744-1430 Fax: +1-408-744-1549 UUCP: ...!uunet!gammafax!mikes CIS: 73747,441
John Stanley <stanley@phoenix.com> (05/18/91)
lemson@ux1.cso.uiuc.edu (David Lemson) writes: > Would someone who actually *knows* please check whether or not there > is an FCC regulation against cellular use in airplanes? I attempted to mail this to the first questioner, but his return address was mangled. FAA: Use of electronic equipment onboard aircraft is covered by Federal Aviation Regulations (FAR) Part 91, Section 91.21. This section prohibits use of any electronic device on board an aircraft, with a VERY short list of exceptions. Para. 91.21(c) specifies who may authorize exceptions and allow other equipment. For holders of an operating certificate (i.e. air carriers) the OPERATOR of the aircraft must make the authorization. This is NOT the pilot. Some have opined that the pilot is the official representative of the operator, but this is contradicted by the next sentence in 91.21(c) which says the pilot or operator may authorize use in other aircraft. If the pilot were authorized to make exceptions to 91.21, there would not be a need to specify 'pilot' as an authorization agent for other aircraft. FCC: The use of land cellular telephones is prohibited by exclusion. Section 2.106 of 47CFR lists frequency allocations by type of service (land mobile, etc.) and 22.902 lists those frequencies allocated to the Domestic Public Cellular Radio Telecommunications Service. The frequencies specified in 22.902 are allocated to land mobile service in 2.106. The FCC issued a Public Notice, clarifying the rules. The text of that notice follows (note that the date is 1984 and some sections of the rules have changed numbers) (also, I have talked to both the people listed as contacts, within the last two months, and the status of the situation is stil the same): PUBLIC NOTICE Federal Communications Commission, 1919 M Street N.W., Washington, D.C. 20554 News Media Information 202/254-7674. Recorded listing of releases and texts 202/632-0002. COMMON CARRIER PUBLIC MOBILE SERVICES INFORMATION CELLULAR UNITS NOT AUTHORIZED FOR AIRBORNE USE Report No. CL-142 October 11, 1984 The Mobile Services Division has received several inquiries regarding the use of cellular mobile and portable units in airplanes and helicopters. The public should be aware that such use on cellular units is _not_ permitted inder the Rules. Use of a cellular unit while airborne is likely to cause serious interference both within the cellular system and in other cellular systems, because an airborne unit will have a transmitting range much greater than the land-based unit for which cellular systems are engineered. Under the Commission's rules, airborne mobile units must be individually licensed for air-ground service and may only communicate through base stations licensed for the 450-MHz air-ground service and may only communicate through base stations frequencies listed in Section 22.521. See also Sections 22.9(c), 22.15(i)(3), and 22.509. There are no cellular frequencies available for air-ground service, and persons owning, installing, or operating airborne cellular units will be subject to enforcement action. For further information, Contact Michael Ferrente on 202 653-5560 or Claudia Borthwick on 202 632-6400. - FCC - _SEE_ Notice of Proposed Rulemaking - CC Docket No. 88-411, FCC 88-278, Released September 2, 1988, 3 FCC Rcd 5265 (1988).
"John R. Covert 18-May-1991 1018" <covert@covert.enet.dec.com> (05/18/91)
>> Warning: Using a Cellular phone on an aircraft is a violation of federal >> law and probably some FAA regulations too. You risk getting arrested. > Yes -- but they don't *tell* you that anywhere, so I assume I'll get > at least one warning (before possible arrest) ... Ah, but they _do_ tell you. Every airline's in-flight magazine has a notice forbidding the use of any electronic devices, especially radios, on board aircraft. And besides, ignorance of the law is not a valid excuse (or so I've always heard). It was my understanding that the relevant FAA regulation (FAR 91.19) prohibits use on Instrument Flight Rules (IFR) flights only (virtually all commercial flights will be IFR) and that the prohibition applies from the point at which the aircraft begins moving under its own power until cancellation of the IFR flight plan (which happens automatically upon landing). When I first got my cellular phone, the commercial pilots I talked to told me that this was the case, and I always turn my phone off when I feel the aircraft being pushed back (even if this is not under the aircraft's own power). However, the FARs, being regulations, can be changed at any time, and you are required by law to abide by them. I'll try to get an actual copy of FAR 91.19 to see what it currently says. I know it talks about electronic devices potentially interfering with BOTH navigation and cockpit communication. A critical issue for ALL radios, including the RECEIVER inside a cellular phone, is what frequencies are used for the injection frequency and the intermediate frequency (IF) of the superheterodyne receiver. In my phone, a Nokia P-30 (equivalent to the Moderator's Radio Shack CT-301), the injection frequency in the first IF stage ranges from 785.88-810.81 MHz, resulting in an IF1 of 83.16 MHz. The second stage injects 82.705 MHz, resulting in an IF2 of 455 kHz. Other phones will be designed to use other frequencies, and any of these frequencies could interfere with equipment aboard the aircraft, not necessarily because of design problems with the equipment, but because these frequencies may actually be used for communications. Any superheterodyne receiver is also a transmitter. The radiated power will be very low, but if you're sitting right on top of the antenna of a device designed to receive at the IF frequencies of your receiver, you will interfere with the other device. I have heard at least two recent reports about airlines telling passengers not to use their phones on aircraft at the gate (the one in Telecom from Chris Schmandt and one from a friend sitting in an American Airlines aircraft at the gate in Dallas/Fort Worth last Thursday), so it is possible that FAR 91.19 has been amended to apply at all times aboard aircraft. I called four airlines: American told me that the rules apply at all times. TWA told me that it was between me and the captain. Delta told me that the rules applied at all times. Continental spent the most time researching it, and told me that it was Continental's interpretation of FAR 91.19 that no electronic devices except those specifically authorized by Continental's corporate headquarters may be used from the time you step over the threshhold of the aircraft until the time you leave the aircraft. The reason stated is that even while on the ground parked at the gate, the flight crew will be in communication, by radio, with the tower to make the flight arrangements. Electronic devices, of which cellular phones are only one, may interfere with cockpit communications. Even if FAR 91.19 doesn't specifically state that the prohibition applies on the ground, there is also a broadly worded FAR which prohibits any kind of "interfering with a flight crew". This regulation essentially requires you to do exactly what you are told, within reason, by any airline employee. Failure to obey the instructions of a flight crew member is a crime punishable by law. john
olsen@xn.ll.mit.edu (05/18/91)
lemson@ux1.cso.uiuc.edu (David Lemson) writes: > Would someone who actually *knows* please check whether or not there > is an FCC regulation against cellular use in airplanes? OK. The FCC frequency allocations table (47 CFR 2.106) allocates the cellular phone frequencies to Land Mobile use. Airborne cellular use (i.e., Aeronautical Mobile) is therefore unauthorized transmission, and is subject to prosecution under the Communications Act of 1934. Note that this argument does not apply to cellular use while on the ground. However, an FAA regulation (14 CFR 91.21) prohibits the use of almost all electronic devices on airliners without the airline's permission, and this applies on the ground as well as in the air. Many airlines have given blanket permission for the use of tape players, portable computers, and similar items, but not for any radio equipment (receiving or transmitting). It is unclear to me whether the pilot has the authority to give this permission on the airline's behalf, but if the pilot says it's OK, no one is likely to bother you about it. The purpose of the FAA regulation is to avoid interference with the aircraft electronics. On the ground this may not be a problem, but airborne, and especially while on approach to landing, it is a risk to be avoided.
Jack.Winslade@uunet.uu.net> (05/19/91)
In a message of <16 May 91 20:45:26>, Ted Marshall writes: >> the navigation equipment. Most airliners now use longer range >> navigation systems like LORAN or various satellite-based systems, >> which can't be upset by FM interference. [...] > This is just plain wrong! Loran-C and GPS (satellite) navigation are > being used in air navigation, but, to my knowledge, mostly in smaller > aircraft. GPS, in particular, cannot be used 24-hours/day because > there are not yet enough satellites in place. Over-ocean operations do > use other forms of navigation, including inertial navigation, but > almost all domestic US enroute navigation is via VOR (VHF > Omnidirectional Range). Also, bad weather approaches into all major > and many minor airports are via ILS (Instrument Landing System). When I was in the Coast Guard I spent more time working with Loran equipment than I care to admit. ;-) Loran-C (the type of Loran that is used today) uses a portion of the frequency spectrum that is SO far from that which cellular phones use that unless the loran receiver is defective, it will be essentially blind to interference from any cellular transmissions on board. Loran-C uses pulse trains of 100 kHz RF. Yes, I said that right. 100 kilohertz -- that's well below the AM broadcast band and almost four orders of magnitude removed from the cellular frequencies. (Loran = 10 ** 5 Hz and cellular is ABOUT 10 ** 9 Hz.) HF transmitters in the kilowatt range are routinely used on ships that navigate with Loran-C, with the HF and loran antennas being quite close to each other. Very seldom will interference (to the loran from the radio transmission) occur in this case, let alone the case of a one to three watt UHF transmitter as in a cellular phone. Now (no grin here) for those of you who happen to live very close to a Loran-C transmitting station, this case of no interference does not hold true the other way around. These transmitters pump out RF pulses in the megawatt range and they have been known to bleed into telephone lines (sounds like an old mechanical teletype running in the background) make one heck of a racket in AM and (sometimes) FM radios, and even cause black and white horizontal 'strobe light' bars on television pictures. Good Day! JSW (Charlie-Golf 1967 - 71) [Moderator's Note: Have you ever traveled through the rural area in northern Wisconsin where the ELF (extremely low frequency) transmitters are located? They send/receive radio transmissions to submarines. The antennas are strung up and down the highway on telephone poles! The frequencies which can travel through the earth and under water are sort of special; they make it possible for a submarine to receive radio signals without having to expose at least a little of itself above water; an important feature when used in a spy operation for military intelligence ... but the base station antenna has to be about a mile in length! PAT]
Jordan Kossack <JKOSS00@ricevm1.rice.edu> (05/19/91)
In article <telecom11.367.6@eecs.nwu.edu>, hpa@casbah.acns.nwu.edu (H. Peter Anvin) writes: > There is a second consideration that prohibites specifically > walkie-talkies, cellphones etc. in carry-on luggage: they are > considered potential helps for terrorists coordinating a hijacking. > You can bring these devices onboard but they have to be in checked > luggage. Well, not to drag this topic out any longer than necessary, but this has not been my experience. On several occasions, I've flown with my handi-talkie in my carry-on bag and I have NEVER been hassled about it nor even asked to show that is actually a radio and not some strange detonator. Mind you, two of these flights were this past Winter when the airports were all worried about security, so I don't think this is something that folk need to worry about these days. Besides, would you trust the baggage handlers with a $400 HT? ;-)
"Michael H. Riddle" <riddle@hoss.unl.edu> (05/19/91)
In <telecom11.369.1@eecs.nwu.edu> ivgate!Jack.Winslade@uunet.uu.net (Jack Winslade) writes: [Most of Jack's comments about HF and Loran-C deleted. Anyone whose idea of a vacation spot is Cape May....] > Now (no grin here) for those of you who happen to live very close to a > Loran-C transmitting station, this case of no interference does not > hold true the other way around. These transmitters pump out RF pulses > in the megawatt range and they have been known to bleed into telephone > lines (sounds like an old mechanical teletype running in the > background) make one heck of a racket in AM and (sometimes) FM radios, > and even cause black and white horizontal 'strobe light' bars on > television pictures. > [Moderator's Note: Have you ever traveled through the rural area in > northern Wisconsin where the ELF (extremely low frequency) > transmitters are located? They send/receive radio transmissions to > submarines. The antennas are strung up and down the highway on > telephone poles! The frequencies which can travel through the earth > and under water are sort of special; they make it possible for a > submarine to receive radio signals without having to expose at least a > little of itself above water; an important feature when used in a spy > operation for military intelligence ... PAT Well, this is getting off the telecom topic a bit, but when I was still in the Air Force I had the job of VLF Systems Integration Manager, and additionally flew as a Communications Control Officer on the SAC Airborne Command Post ("Looking Glass"). We had VLF transmit capability, but our antenna wasn't a mile long. We always had at least 27,000 feet (five miles, more or less) of wire on the reel at takeoff. If we had to extend to transmit, the actual length was frequency dependent but was measured in miles, not feet, for lay purposes. We were using 30-60 kHz. The ELF is down in the 3 - 30 kHZ range, so I suspect the Wisconsin site antennas are bigger than merely one mile and/or are loaded substantially. With sufficient loading, and long ground-plane radials, the actual "in the air" portion of some VLF ground transmitters doesn't have to be more than 2000 feet or so. It all depends on how you design it to meet whatever goals you are addressing. (Historic interlude. If I remember correctly, Marconi's original station on Cape Cod was a VLF installation.) Incidentally, we never extended our VLF antenna over land during peacetime, which is to say we always practiced over water. The SAC airborne used the transverse electric component, so we basically dragged the antenna "straight" behind us. (Obviously, there was a droop.) Some other airborne VLF transmitters would fly in predetermined circles to get a "straight" drop and maximize the transverse magnetic component. Pat's comments about "spy" operation aren't quite on point. Equally important is the invisibility (and hence invulnerability) of the SSBN force (sub-launched ballistic missiles). Finally, in regards to the part of the thread about environmental impact and Jack's comments about receving Loran in TV's, radios and maybe teeth fillings, there was a great deal of opposition to the Wisconsin site because of anticipated interence and unknown long-term effects to low level low frequency radiation. Recent EPA reports, while not yet admitting cause and effect, reinforce the need for concern and study even with power lines. As I remember, the Wisconsin site was scaled back after the protests. I haven't heard what, if any, day-to-day interference they have actually observed. <<<< insert standard disclaimer here >>>> riddle@hoss.unl.edu | Nebraska Inns of Court ivgate!inns!postmaster@uunet.uu.net | +1 402 593 1192 Sysop of 1:285/27@Fidonet | 3/12/24/9600/8N1/V.32/V.42bis
John Stanley <stanley@phoenix.com> (05/20/91)
floyd@ims.alaska.edu (Floyd Davidson) writes: > (Some day I'll tell you how I learned that > Loran C can be 60 degrees off. No problem, just makes the pilot eyes > get large when he breaks out of the clouds ...) It is not hard. I live withing flying distance of the master station for the 9960 (Northeast) chain of Loran. One of the standard airways between Syracuse and Buffalo passes right over it. During my last flight to Buffalo on that airway (using VOR's and not LORAN for navigation) the LORAN told me that I was alternately going north, south, east or west at anywhere from 200 to 400 knots, for the entire last half of the flight. The display updates about every six seconds, and turning from north at 400 knots to south at 400 knots withing six seconds would certainly exceed the G limits of the airplane, if not the limits of the human body. This was in a Cessna 172. The 'never exceed' speed is about 130 knots, and this aircraft cannot reach that speed in level flight.
Mike Ardai <ardai@teda.eda.teradyne.com> (05/20/91)
In article <telecom11.368.2@eecs.nwu.edu> Mike Spann <mikes@gammalink. com> writes: > Digging way back into my memory, I do remember a story (maybe even > true) where police officers were told not to dump their spare bullets > into the same bag as their hand held radios. The story I was told was > that should the push-to-talk button be pressed, the electro-magnetic > waves could cause a round to go off. [This is getting rather far from Telecom...] Actually, it is much simpler than that. Most handheld radios have metal contacts on the bottom for recharging. Putting one of them into the same pocket as bullets will cause the bullets to short out the charging studs. This will heat them up and cause them to fire. I seem to rememeber that a cop shot himself that way back in the 70's in NYC. (I had a similar experience with some keys and my ICOM - they sure got hot :-) Michael L. Ardai N1IST Teradyne EDA East sun!teda!ardai (preferred) or ardai@bu-pub.bu.edu
"H. Peter Anvin" <hpa@casbah.acns.nwu.edu> (05/20/91)
In article <telecom11.377.9@eecs.nwu.edu> of comp.dcom.telecom, Jordan Kossack <JKOSS00@ricevm1.rice.edu> writes: > In article <telecom11.367.6@eecs.nwu.edu>, hpa@casbah.acns.nwu.edu (H. > Peter Anvin) writes: >> There is a second consideration that prohibites specifically >> walkie-talkies, cellphones etc. in carry-on luggage: they are >> considered potential helps for terrorists coordinating a hijacking. >> You can bring these devices onboard but they have to be in checked >> luggage. > Well, not to drag this topic out any longer than necessary, but > this has not been my experience.... > Besides, would you trust the baggage handlers with a $400 HT? ;-) I have been asked to qualify where my experience from this comes. I have experienced this on two flights; one in Europe (Milano-Copenhagen I believe); that was the case where they would not even let onboard a wire-bound walkie-talkie lookalike. On a recent (March 91) flight on American Airlines I asked the check-in representatives about my 144 MHz ham handietalkie; they said I could take it onboard only if I put it in the check-in luggage. [Moderator's Note: This thread has gotten quite far from telecom, so unless there is something really new and different not yet posited by the readers, let's close it out. Thanks. PAT]