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CB Radios, Cellphones and Gasoline Vapor Ignition
Claims that people have started fires by using
their cell phone while refueling a car apparently are false: See http://www.snopes.com/autos/hazards/gasvapor.asp and other sites. However, the first radios transmitted sparks, so in principle it should be possible to transmit near a long wire separated by a small gap from ground or another wire and get a small spark. So, I decided to try an experiment. I don't use a cell phone, so I assumed a CB radio transceiver would be a reasonable substitute: The power output of a nominal 5 W CB also is consistent and nonadaptive, so a possible unknown (actual output power) is avoided. Cell phones are adaptive and not very consistent in power output, so power should be monitored during a cell phone experiment. 5 W is considerably more than the 0.2 to 2 W typically possible from a cell phone; the power should be the important factor, although maybe someone should repeat this experiment with a cell phone, which would operate at a much higher frequency. I used a Radio Shack TRC-231 handheld (stock #21-1675) with xmit power on high and set on Channel 40. The antenna was the one that came with it (about 25 cm long). I set the volume to max and the squelch at min to be able to detect anyone else trying to use the channel; this was just to be sure that my brief, silent transmissions would not interfere with anyone. I used the CB indoors, in a mostly metal-shielded room. Because CB wavelength is around 10 m, everything I did was in the near field; however, the inverse square law for power still holds, allowing that the CB antenna is more of a line than a point source under my conditions below. The first thing I noticed was that every time I keyed the transmit button, the CB would switch the light level of a nearby touch-dimmed lamp, and it made a Microalert microwave detector scream. I unplugged the lamp and turned off the Microalert. Then, I tried to light a 120VAC indicator neon lamp attached to two solid copper switchback wires totalling about 1 m long, so the lamp was in the middle effectively of a dipole antenna. I tested the lamp and found it would light with 10 microamps current. The CB had no effect, even if held parallel to, and almost touching, the wires. Thus, the near field of a 5 W CB radio can not supply about 90 V at even 10 uA, under these conditions. I then attached a 1.2 m monopole antenna to an oscilloscope. This antenna has a Schottky hot carrier diode and impedance matching resistors builtin. It's home made, but it's probably as good as any other wire about that long. I hooked the antenna coax to an oscilloscope: With the CB transmitting, and its antenna parallel and 1 m away from the monopole, the amplitude was about 100 mV p-p, at 27 MHz or so. I could not get more amplitude no matter how close I held the CB, or at what angle. Touching the bare monopole wire increased the amplitude by no more than 10%. So, first conclusion: To get even a 1 V spark would take a wire at least 9 m long, all somehow kept within 1 m of the transmitter. Thus, it appears it is not feasible to create a hazardous spark with a CB at a gas station. Just to be sure, I taped a 1 m wire to a table top in the dark and slowly brought it closer and closer to another wire plugged into a wall socket 3rd wire ground (yes, I verified that the socket was wired to ground first!). At each distance, I briefly keyed the CB. I could not see any spark, even after dark-adapting my eyes for 10 min and letting the wires touch. I might have dark-adapted longer, but I don't know whether I should have been able to see a 50 mV spark or not. So, I think sliding over on a car seat, and thus generating a possible static charge, would be more likely to ignite gasoline vapor than talking on a cell phone while refueling. However, it would be useful for someone to repeat this kind of test with an actual cell phone, as opposed to a CB radio. The wires should be shorter, for one thing . . .. I'm cross posting to an antenna group, looking for criticism. John John Michael Williams |
I was struck by a thought when I heard the latest Palestinian
terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... ROTFLMAO! ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | John "Peace for our Time" Kerry, Neville Chamberlain of this Century |
"John Michael Williams" wrote in message
m... Claims that people have started fires by using their cell phone while refueling a car apparently are false: See http://www.snopes.com/autos/hazards/gasvapor.asp and other sites. However, the first radios transmitted sparks, so in principle it should be possible to transmit near a long wire separated by a small gap from ground or another wire and get a small spark. So, I decided to try an experiment. I don't use a cell phone, so I assumed a CB radio transceiver would be a reasonable substitute: The power output of a nominal 5 W CB also is consistent and nonadaptive, so a possible unknown (actual output power) is avoided. Cell phones are adaptive and not very consistent in power output, so power should be monitored during a cell phone experiment. 5 W is considerably more than the 0.2 to 2 W typically possible from a cell phone; the power should be the important factor, although maybe someone should repeat this experiment with a cell phone, which would operate at a much higher frequency. I used a Radio Shack TRC-231 handheld (stock #21-1675) with xmit power on high and set on Channel 40. The antenna was the one that came with it (about 25 cm long). I set the volume to max and the squelch at min to be able to detect anyone else trying to use the channel; this was just to be sure that my brief, silent transmissions would not interfere with anyone. I used the CB indoors, in a mostly metal-shielded room. Because CB wavelength is around 10 m, everything I did was in the near field; however, the inverse square law for power still holds, allowing that the CB antenna is more of a line than a point source under my conditions below. The first thing I noticed was that every time I keyed the transmit button, the CB would switch the light level of a nearby touch-dimmed lamp, and it made a Microalert microwave detector scream. I unplugged the lamp and turned off the Microalert. Then, I tried to light a 120VAC indicator neon lamp attached to two solid copper switchback wires totalling about 1 m long, so the lamp was in the middle effectively of a dipole antenna. I tested the lamp and found it would light with 10 microamps current. The CB had no effect, even if held parallel to, and almost touching, the wires. Thus, the near field of a 5 W CB radio can not supply about 90 V at even 10 uA, under these conditions. I then attached a 1.2 m monopole antenna to an oscilloscope. This antenna has a Schottky hot carrier diode and impedance matching resistors builtin. It's home made, but it's probably as good as any other wire about that long. I hooked the antenna coax to an oscilloscope: With the CB transmitting, and its antenna parallel and 1 m away from the monopole, the amplitude was about 100 mV p-p, at 27 MHz or so. I could not get more amplitude no matter how close I held the CB, or at what angle. Touching the bare monopole wire increased the amplitude by no more than 10%. So, first conclusion: To get even a 1 V spark would take a wire at least 9 m long, all somehow kept within 1 m of the transmitter. Thus, it appears it is not feasible to create a hazardous spark with a CB at a gas station. Just to be sure, I taped a 1 m wire to a table top in the dark and slowly brought it closer and closer to another wire plugged into a wall socket 3rd wire ground (yes, I verified that the socket was wired to ground first!). At each distance, I briefly keyed the CB. I could not see any spark, even after dark-adapting my eyes for 10 min and letting the wires touch. I might have dark-adapted longer, but I don't know whether I should have been able to see a 50 mV spark or not. So, I think sliding over on a car seat, and thus generating a possible static charge, would be more likely to ignite gasoline vapor than talking on a cell phone while refueling. However, it would be useful for someone to repeat this kind of test with an actual cell phone, as opposed to a CB radio. The wires should be shorter, for one thing . . .. I'm cross posting to an antenna group, looking for criticism. John John Michael Williams It's a bit of a stretch to think that cell-phones are a problem, whereas the car driving off next to you, with a set of spark plugs going for their lives, is not. Hmmmm. Ken |
John, It's also possible to start a fire rubbing two sticks together, but it isn't as likely to be an accidental thing. I would tend to doubt any claims about cell phones starting accidental fires unless there has been some modification to the phone, or other unusual circumstance. Turning off cell phones and radios seems like a reasonable precaution while fueling, I don't have a problem with that. I also don't understand why anyone else would either. Do I turn off my two way radio when fueling? Yes, but mainly because of how it's connected (ignition switch). If fuel vapor liable to ignite because of RF? Not unless the RF field is very strong, or the antenna arcs for some reason. Very likely? Not really. Possible? Sure. So using a little common sense... what's the problem? 'Doc PS - Cross posting is a sure way of causing misunderstandings. |
I noticed that the appearance of the no cell phone signs came around the
same time that gas stations started running audio commercials through speakers at the pump. |
John Michael Williams wrote:
SNIP However, the first radios transmitted sparks, so in principle it should be possible to transmit near a long wire separated by a small gap from ground or another wire and get a small spark. So, I decided to try an experiment. SNIP There is one other potential source for a spark that you did not investigate. A make/break contact in a switch causes sparks when opened. The US Military specifies special shielded switches for their explosive, gas vapor, etc., environments. So, it is possible that pressing the PTT or the ON/OFF switch causes the necessary spark. Remember the Apollo ground fire. A switch/spark caused an oxygen explosion. |
"Dave Shrader" wrote in message news:Xu36c.33004$po.292953@attbi_s52... John Michael Williams wrote: SNIP However, the first radios transmitted sparks, so in principle it should be possible to transmit near a long wire separated by a small gap from ground or another wire and get a small spark. So, I decided to try an experiment. SNIP There is one other potential source for a spark that you did not investigate. A make/break contact in a switch causes sparks when opened. The US Military specifies special shielded switches for their explosive, gas vapor, etc., environments. So, it is possible that pressing the PTT or the ON/OFF switch causes the necessary spark. Remember the Apollo ground fire. A switch/spark caused an oxygen explosion. I wouldn't call it an "oxygen explosion" but a small fire that grew rapidly due to the pure-oxygen atmosphere. |
Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... If they could figure out from whom they're buying all them pre-paid cellphones (in order to generate the number lists), it could work. Just keep it running 24/7 with a "Sorry, wrong number" message in case an innocent (or unfinished bomb) answers. I figure eventually they'll run out of suicide-bomb volunteers. Might as well help if it can be done without blowing anyone else up. Mark L. Fergerson |
On Wed, 17 Mar 2004 13:08:33 -0700, Jim Thompson
wrote: I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... ROTFLMAO! Yes, I'm rolling on the floor laughing at all these deaths, too, as I'm sure we all are. -- The BBC: Licensed at public expense to spread lies. |
"Paul Burridge" wrote : Jim Thompson wrote: : : I was struck by a thought when I heard the latest Palestinian : terrorist trick is to send a kid through the border with a back-pack : bomb triggered by a cell phone.... : : The Israelis should get a telemarketer's speed dialer and constantly : dial away... boom... boom... boom... : : ROTFLMAO! : : Yes, I'm rolling on the floor laughing at all these deaths, too, as : I'm sure we all are. Huh? He seemed to be laughing at the lame Idea! I also thought it funny that anyone would try something which would almost totally wipe out the cellular phone service for the entire country... All to provide a SMALL measure of confidence that no one had a bomb attached to a phone. Like it would even work! WTH are you referring to? GAL! |
Better not open your door or have someone else open theirs next to yu then.
That dome light switch might get you. "Dave Shrader" wrote in message news:Xu36c.33004$po.292953@attbi_s52... So, it is possible that pressing the PTT or the ON/OFF switch causes the necessary spark. Remember the Apollo ground fire. A switch/spark caused an oxygen explosion. |
"Ken Taylor" wrote:
[snip] It's a bit of a stretch to think that cell-phones are a problem, whereas the car driving off next to you, with a set of spark plugs going for their lives, is not. Hmmmm. Quite. Not only that, but a petrol station I used to live near had an in-store bakery. Tim -- Love is a travelator. |
In rec.radio.amateur.antenna,
( I suppose this is on RRAA because cell phones have antennas ) sci.electronics.design,sci.electronics.basics, Jim Thompson wrote: I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... Call phones have become the trigger of choice for terrorist bombs. The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... This might already be illegal there (not that that would stop a government). I've heard that various parts of Europe have much stronger privacy laws than the US, so there's little or no telemarketing. ROTFLMAO! Of course, in the USA, one could put the cell number on the national DO-NOT-CALL list, then only an "illegal" telemarketer would trigger the bomb. Bombers might figure ways around this (especially if they search Usenet), such as a cellphone answering circuit and a "dee tee em eff" decoding circuit. I wouldn't want to spell it out for them... ...Jim Thompson ----- http://mindspring.com/~benbradley |
On Wed, 17 Mar 2004 13:08:33 -0700, Jim Thompson
wrote: I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... ROTFLMAO! ...Jim Thompson The terrorist will just make 'em more sophisticated. Like once you dialup the cellphone you have to enter a N digit code followed by the * key before the bomb detonates...123456789*...BOOM!!! Remove "HeadFromButt", before replying by email. |
IIRC, the Apollo capsule wire insulation was FEP, and was ignited when the
power conductor it insulated was mechanically pinched and shorted to ground. It overheated enough from fault current to ignite before the breaker tripped. Kapton tape was blamed in the Swissair 400(?) cockpit fire and crash in Newfoundland(?) a few years back. Gasoline vapor fuel fires were ignited by early pagers and first generation cell phones which used tiny universal motors with eccentric weights as silent ring annunciators. Find one of those old beasts and try running that motor in a flammable environment. The technical basis of this is covered in a text: "Intrinsic Safety" by Redding, published by Mc Graw Hill. -- Crazy George Remove N O and S P A M imbedded in return address "DarkMatter" wrote in message ... On Wed, 17 Mar 2004 21:33:43 GMT, Dave Shrader Gave us: So, it is possible that pressing the PTT or the ON/OFF switch causes the necessary spark. Both in handheld radio transceivers, and cell phones, there are NO switches that pass any power level that causes a spark to exhibit upon contact or release. Sheesh. Remember the Apollo ground fire. It was a pure oxy environment. There was, as a rule nothing flammable on board. The problem was that materials were not tested for their flammability in such an oxy rich environ. The kapton tape is what was set afire by the spark, and that fire grew ferociously in the oxygen. The oxygen was the oxidizer, not what burned. A switch/spark caused an oxygen explosion. Are you sure you aren't just pulling that one out of you ass as well? I was taught that it was the spark caused by a dropped wrench, and that tape is what burned. An explosion would have blown the craft open from the inside. That did not happen. One would think that all the switches on Apollo were already gas tight. |
On Wed, 17 Mar 2004 13:08:33 -0700, Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... ROTFLMAO! ...Jim Thompson Had the liberals not f'd everything up, this would've been a common counter-terror measure. You place radio transmitters at sensitive locations to blow up car bombs before they got close enough to do damage. The theory is that if the tango pusses out, another tango remote detonates the bomb, so all bombs have a radio failsafe. -- Best Regards, Mike |
On Wed, 17 Mar 2004 16:35:02 -0700, Mark Fergerson wrote:
Jim Thompson wrote: I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... If they could figure out from whom they're buying all them pre-paid cellphones (in order to generate the number lists), it could work. Just keep it running 24/7 with a "Sorry, wrong number" message in case an innocent (or unfinished bomb) answers. I figure eventually they'll run out of suicide-bomb volunteers. Might as well help if it can be done without blowing anyone else up. Mark L. Fergerson Do you all think that tangos are dumb enough to trigger the bomb with the ringer or would the detonator answer first and listen for a DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just as he's connecting the thing. -- Best Regards, Mike |
On Thu, 18 Mar 2004 00:09:30 GMT, Roger Gt wrote:
"Paul Burridge" wrote : Jim Thompson wrote: : :I was struck by a thought when I heard the latest Palestinian :terrorist trick is to send a kid through the border with a back-pack :bomb triggered by a cell phone.... : :The Israelis should get a telemarketer's speed dialer and constantly :dial away... boom... boom... boom... : :ROTFLMAO! : : Yes, I'm rolling on the floor laughing at all these deaths, too, as : I'm sure we all are. Huh? He seemed to be laughing at the lame Idea! I also thought it funny that anyone would try something which would almost totally wipe out the cellular phone service for the entire country... does a 200 station phone room with auto-dialers all calling one state wipe out POTs? WTH are *you* talking about? All to provide a SMALL measure of confidence that no one had a bomb attached to a phone. Like it would even work! WTH are you referring to? GAL! -- Best Regards, Mike |
On 17 Mar 2004 12:02:15 -0800, John Michael Williams wrote:
Claims that people have started fires by using their cell phone while refueling a car apparently are false: See http://www.snopes.com/autos/hazards/gasvapor.asp and other sites. There was discussion of this and bad electric fuel pump designs last year, but I don't recall anyone testing it out. snip So, I think sliding over on a car seat, and thus generating a possible static charge, would be more likely to ignite gasoline vapor than talking on a cell phone while refueling. It is more likely and there's a gas station here that has a memo to that effect (static - mainly in winter) posted where the customers can *not* see it, duh! No signs on the pumps... The memo says you should shock yourself on the car befor going to the pump. No one thought about the vapor from the car on the other side of the island. However, it would be useful for someone to repeat this kind of test with an actual cell phone, as opposed to a CB radio. The wires should be shorter, for one thing . . .. I'm cross posting to an antenna group, looking for criticism. John John Michael Williams -- Best Regards, Mike |
On Wed, 17 Mar 2004 19:16:45 -0800, DarkMatter wrote:
On Thu, 18 Mar 2004 10:02:37 +1300, "Ken Taylor" Gave us: snipped previous It's a bit of a stretch to think that cell-phones are a problem, whereas the car driving off next to you, with a set of spark plugs going for their lives, is not. Hmmmm. Yes, I agree. At 40kV these days too, and sure... none of that closed system leaks anywhere.... sure. It is ten orders of magnitude more dangerous than any handheld (or ear held) transmitter is to flammable liquid vapors. One should turn one's engine off whenever not using the car, let alone at fuel pump islands. Always! The old adage that it costs more to restart an engine than to leave it running is bull**** today. Fuel injected (or throttle body)cars do not suffer the idle mixture swings or flooding risk of old carbureted engines. Unless you are in a very very cold place, turn your friggin' engine off when you aren't driving the friggin' car! The guy next to you with the dangling plug wire arcing away, though. Make me more determined to have fuel delivered to a home tank. I got yelled at for leaving the engine running at a deisel pump once. Some people just don't know how hard t is to ignite the stuff. -- Best Regards, Mike |
On Wed, 17 Mar 2004 13:33:06 -0800, Guy Macon wrote:
"John Michael Williams" wrote: Thus, it appears it is not feasible to create a hazardous spark with a CB at a gas station. So, I think sliding over on a car seat, and thus generating a possible static charge, would be more likely to ignite gasoline vapor than talking on a cell phone while refueling. Excellent set of experiments! I heartily approve of anyone who does an experiment rather than taking someone's word. Yeah. Amazing how much BS gets foisted on people. Your methodology seems sound to me. You might try putting a couple of drops of gasoline on a ceramic plate and seeing if your wire is making a spark too small to see but large enough to ignite the gasoline. It's the vapor you want to try to ignite, so conditions will vary depending on the wind. temperature, and pump rate which iis coutered by the new vapor recovery systems installed on pumps. I think the dangling plug wire is more dangerous than even smoking at the pump. Ever throw a lit cigarette in a pail of gas. The cig gets extinguished. Another way of looking at it is with statistics. How many people talk on cell phones while refueling? How many fuel fires occur? --------------------------------------------------------------- |'Doc says... |Turning off cell phones and radios seems like a reasonable |precaution while fueling, I don't have a problem with that. |I also don't understand why anyone else would either. You don't understand why someone might be unwilling to miss an incoming call when there is no apparent benefit? -- Best Regards, Mike |
On Wed, 17 Mar 2004 13:33:06 -0800, Guy Macon wrote:
snip |'Doc says... |Turning off cell phones and radios seems like a reasonable |precaution while fueling, I don't have a problem with that. |I also don't understand why anyone else would either. You don't understand why someone might be unwilling to miss an incoming call when there is no apparent benefit? Uh, a local Pastor's douche-bag wife recently backed over a BP station clerk here (while he was measuring the pumps) and drove off. He's in friggin' pain. Cops pulled the snotty bitch over and she claimed she didn't know she'd run over him. Was it the cell phone or the blaring xtian music? -- Best Regards, Mike |
On Wed, 17 Mar 2004 21:50:35 -0600, Crazy George wrote:
IIRC, the Apollo capsule wire insulation was FEP, and was ignited when the power conductor it insulated was mechanically pinched and shorted to ground. It overheated enough from fault current to ignite before the breaker tripped. Kapton tape was blamed in the Swissair 400(?) cockpit fire and crash in Newfoundland(?) a few years back. Gasoline vapor fuel fires were ignited by early pagers and first generation cell phones which used tiny universal motors with eccentric weights as silent ring annunciators. My Motorola Classic has one of those. What are they using now? Find one of those old beasts and try running that motor in a flammable environment. OK ;) The technical basis of this is covered in a text: "Intrinsic Safety" by Redding, published by Mc Graw Hill. -- Best Regards, Mike |
"Active8" wrote : Roger Gt wrote: : "Paul Burridge" wrote : : Jim Thompson wrote: : : : :I was struck by a thought when I heard the latest Palestinian : :terrorist trick is to send a kid through the border with a : back-pack : :bomb triggered by a cell phone.... : : : :The Israelis should get a telemarketer's speed dialer and : constantly : :dial away... boom... boom... boom... : : : :ROTFLMAO! : : : : Yes, I'm rolling on the floor laughing at all these deaths, too, : as : : I'm sure we all are. : : Huh? : He seemed to be laughing at the lame Idea! I also thought it : funny that anyone would try something which would almost totally : wipe out the cellular phone service for the entire country... : : does a 200 station phone room with auto-dialers all calling one : state wipe out POTs? WTH are *you* talking about? Gee - Primitive! Not a Telephone guy I guess...... The last autodialer I worked on was a Dual DS3 line unit with a router. 2 times 864 lines wide. A few of those would really choke a network! : All : to provide a SMALL measure of confidence that no one had a bomb : attached to a phone. Like it would even work! : WTH are you referring to? GAL! : : Best Regards, : Mike |
Active8 wrote:
[bombs] Do you all think that tangos are dumb enough to trigger the bomb with the ringer or would the detonator answer first and listen for a DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just as he's connecting the thing. I very much doubt they bother with DTMF decoders. I mean, how often do you get a wrong number? I've had about 4 in my life. They'll just connect the ringer (or vibrate function) to the detonator (with whatever minimal circuitry in between is required - I've never used a detonator!) and then only turn the phone on at the last minute. It's not dumb to design a remote detonation system that requires the absolute minimum of specialist knowledge and equipment to construct. Tim -- Love is a travelator. |
Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... You would have to have every phone in the nation ring every couple of hours. They're not going to be stupid enough to have the phone both switched on and connected to the bomb until the last minute. Tim -- Love is a travelator. |
Guy, I don't understand why anyone would have a cell phone stuck in their ear every waking moment, especially in a car, or while fueling, or in a number of other places where I've seen them. They can be and are a hazard while driving, and a real P.I.T.A. in public places. (Hurray for the states that passed a 'no cell phone while driving' law!) Seriously, how many ~important~ calls have you ever had on your cell phone when in a public place, or while driving that couldn't have waited? Cell phones should be water soluble, or biodegradable... 'Doc |
'Doc wrote in message ...
John, It's also possible to start a fire rubbing two sticks together, but it isn't as likely to be an accidental thing. I would tend to doubt any claims about cell phones starting accidental fires unless there has been some modification to the phone, or other unusual circumstance. Turning off cell phones and radios seems like a reasonable precaution while fueling, I don't have a problem with that. I also don't understand why anyone else would either. Do I turn off my two way radio when fueling? Yes, but mainly because of how it's connected (ignition switch). If fuel vapor liable to ignite because of RF? Not unless the RF field is very strong, or the antenna arcs for some reason. Very likely? Not really. Possible? Sure. So using a little common sense... what's the problem? 'Doc PS - Cross posting is a sure way of causing misunderstandings. I was just trying to add some factual information to the link I gave, which was just a lot of rumor--both pro and con RF hazards. Check it out. From time to time, I read postings about people complaining about others gabbing on a cell phone while (self-serve) refueling. I don't follow what you say about cross-posting. I'm not a ham operator, so if I am making some obvious mistake, I thought adding the antenna group would get a correction. Is that your interest? Hopefully, this thread will end up by putting to rest fears of cell phones around gas stations, at least from the RF standpoint. Also, if I'm wrong, and there IS danger from the RF, someone should be able to correct me. Either way, it's an interesting topic, don't you think? John John Michael Williams |
On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton
tim.auton@uton.[groupSexWithoutTheY] wrote: Do you all think that tangos are dumb enough to trigger the bomb with the ringer or would the detonator answer first and listen for a DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just as he's connecting the thing. I very much doubt they bother with DTMF decoders. I mean, how often do you get a wrong number? I've had about 4 in my life. They'll just connect the ringer (or vibrate function) to the detonator (with whatever minimal circuitry in between is required - I've never used a detonator!) and then only turn the phone on at the last minute. It's not dumb to design a remote detonation system that requires the absolute minimum of specialist knowledge and equipment to construct. To use the unique cellphone ID to detonate a remote bomb is actually a very ingenious innovation. No timers to mess with. The terrorist has full and instant control of the time and place to set off the bomb. As Tim says its relatively easy to connect the ringer wires to a simple circuit to output enough juice to trigger the detonator. Frist year student project - like using a battery to keep a capacitor charged and the ringer closes the discharge switch. Boom. The countermeasure I think, is fairly simple. Every vulnerable public place which may be targeted by terrorist bomb attacks, should install cellphone signal blockers. I believe these are already available and smart dining places and concert halls have them so that their patrons won't be interrupted by cellphones. I'll skip the arguments, mostly from cellphone service providers, against signal blockers that may cause doctors and emergency workers to miss their calls. Until some better solution comes along I think this is a good solution. (Hint. Buy shares in signal blocker companies.) If this suggestion is taken up perhaps we'll get some peace from those incurable cellphone yakkers who think the world wants to hear every word they say anywhere. |
"KLM" wrote in message ... On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton tim.auton@uton.[groupSexWithoutTheY] wrote: The countermeasure I think, is fairly simple. Every vulnerable public place which may be targeted by terrorist bomb attacks, should install cellphone signal blockers. Not in the US. Intentional interference is illegal. It likely is in most places. |
On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton
tim.auton@uton.[groupSexWithoutTheY] wrote: Active8 wrote: [bombs] Do you all think that tangos are dumb enough to trigger the bomb with the ringer or would the detonator answer first and listen for a DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just as he's connecting the thing. I very much doubt they bother with DTMF decoders. I mean, how often do you get a wrong number? I've had about 4 in my life. They'll just connect the ringer (or vibrate function) to the detonator (with whatever minimal circuitry in between is required - I've never used a detonator!) and then only turn the phone on at the last minute. It's not dumb to design a remote detonation system that requires the absolute minimum of specialist knowledge and equipment to construct. Tim New anti-terrorist weapon = telemarketers. They call everybody. Should wipe out the bomb makers in about a week. Dave Head |
|
Jim Thompson wrote:
I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... Not really. The technology is far better. Here you can get those industial mobiles with a serial output. You can send an SMS which's string can be decoded by software of you own microcontroller. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net |
On Thu, 18 Mar 2004 14:08:26 +0100, the renowned Rene Tschaggelar
wrote: Jim Thompson wrote: I was struck by a thought when I heard the latest Palestinian terrorist trick is to send a kid through the border with a back-pack bomb triggered by a cell phone.... The Israelis should get a telemarketer's speed dialer and constantly dial away... boom... boom... boom... Not really. The technology is far better. Here you can get those industial mobiles with a serial output. You can send an SMS which's string can be decoded by software of you own microcontroller. One could easily imagine a semi-smart anti-convoy bomb that could be remotely triggered by a hidden operator to go off after a programmable delay (with password), so signal jamming would be relatively ineffective. Nasty, and hobbyist-level technology once you have the phone. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
In message , Guy Macon
writes [Snipped] It's silly to worry about cell phones when every car that drives in has a high-voltage ignition system under the hood, 12V spark-producing switches in the door frames, and a hot catalytic converter underneath the car. The RF/electrical bit seems like a red herring to me, but I suppose it would be better to give full attention to the flammable liquid you're pumping rather than a telephone conversation. -- Syd Rumpo |
On Wed, 17 Mar 2004 21:33:43 GMT, Dave Shrader
wrote: John Michael Williams wrote: SNIP However, the first radios transmitted sparks, so in principle it should be possible to transmit near a long wire separated by a small gap from ground or another wire and get a small spark. So, I decided to try an experiment. SNIP There is one other potential source for a spark that you did not investigate. A make/break contact in a switch causes sparks when opened. The US Military specifies special shielded switches for their explosive, gas vapor, etc., environments. This reminds me of a story... (pause while room clears out). Years ago I was an engineering student working for Cadillac Motor Car. Electronic fuel injection was new then, and there had been a couple of fires in the field that were suspected to have been caused by leaky fuel lines, which were at higher pressure than on the old carbureted cars. There were competing theories, however, as to what exactly was setting off the fire. I got assigned to help the guy doing the experiments to find out. He had a car fitted with a plexiglas hood, topped by a small tower with a high-speed movie camera pointing down for a good look at anything happening in the engine compartment. Two fire extinguishers were arranged to cover the under-hood area, and a fuel vapor sensor was also installed there. The way it was supposed to work was that he would drive and I would operate the hand-pumped sensor, and at the first sign of fire he would trigger the extinguishers. We ran all the tests at the GM Proving Grounds in Milford, Michigan. We tried making leaks in the fuel injection hoses. We had gas spraying all over under the hood, collecting in pools on the hot exhaust manifold. We tried poking holes in the spark plug wire insulation. Nothing, no fire. Finally I got a bright idea, and loosened the ground for the air conditioner compressor clutch. The idea was that this was a big inductor, and if the circuit opened there would be a big spark. Then all we needed to do was get the wire to bounce. We tried swerving from side to side, and driving on bumpy tracks, but no deal. I was *sure* that this spark would do the job, but we couldn't tell if we were really getting the spark. So finally I stood on the hood, holding on to the camera tower, so I could see for myself if there were sparks. He drove down the bumpy road one more time, and I did in fact see a spark: The high-speed movie shows the fire spreading out from it, more and more on each frame. Also on each frame was the back of my head, moving away more and more on each frame, until the extinguishers doused everything. What a rush! Them was the good ole' days..... Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis www.daqarta.com |
Paul Burridge wrote:
I've never been blown up yet. You've never died yet, either. :-) -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
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One thing that may set off a detonator is a RF field with a wavelength in
the order of the detonator leads. From the time I worked with detonators on oilrigs, an absolute radio-silence was required till the charge was safely lowered down the borehole. Wim |
On Thu, 18 Mar 2004 10:30:45 GMT, Dave Head wrote:
On Thu, 18 Mar 2004 05:39:21 +0000, Tim Auton tim.auton@uton.[groupSexWithoutTheY] wrote: Active8 wrote: [bombs] Do you all think that tangos are dumb enough to trigger the bomb with the ringer or would the detonator answer first and listen for a DTMF sequence. Hmmm? Achmed the bomb maker gets a wrong number just as he's connecting the thing. I very much doubt they bother with DTMF decoders. I mean, how often do you get a wrong number? I've had about 4 in my life. They'll just connect the ringer (or vibrate function) to the detonator (with whatever minimal circuitry in between is required - I've never used a detonator!) and then only turn the phone on at the last minute. It's not dumb to design a remote detonation system that requires the absolute minimum of specialist knowledge and equipment to construct. Tim New anti-terrorist weapon = telemarketers. They call everybody. Should wipe out the bomb makers in about a week. Dave Head Not if they're on the Do Not Call list ;) -- Best Regards, Mike |
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