Cell phone jammer wanted!!
Jun 2nd, 2006, 07:11 AM
#41
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I use my 5-6yr old Sennheisers on every flight I take and wouldn't travel without them.
I don't know the model #, and it's probably obsolete now anyway. Small, fold up, great audio quality, batteries last 20-30hrs of usage (I carry replacement batteries in the case).
I just wish the ability to cancel out high frequency white noise was as good as the low freq engine noise. Some planes have a high pitch engine whine, others have high pitched ventilation noise, and others have too much high frequency babble noise sitting in the row behind me.
I don't know the model #, and it's probably obsolete now anyway. Small, fold up, great audio quality, batteries last 20-30hrs of usage (I carry replacement batteries in the case).
I just wish the ability to cancel out high frequency white noise was as good as the low freq engine noise. Some planes have a high pitch engine whine, others have high pitched ventilation noise, and others have too much high frequency babble noise sitting in the row behind me.
Jun 2nd, 2006, 10:19 AM
#42
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Robespierre, you need to go to the individual reviews of each headphone if you want more detail. There really is no argument here - they are both good products.
I bought my Bose when they first came out, and have been very happy with them. Being over-the-ear headphones, they block out some noise even with the circuitry turned off during takeoff and landing. Another thing I like is that the batteries and noise cancelling circuitry are self contained in the earpieces rather than hanging from the wire.
Your Sennheisers have some advantages over the Bose, including their lightness. As for sound quality, well, if you disagree with CNET, fine. As long as you are happy that's all that matters.
I bought my Bose when they first came out, and have been very happy with them. Being over-the-ear headphones, they block out some noise even with the circuitry turned off during takeoff and landing. Another thing I like is that the batteries and noise cancelling circuitry are self contained in the earpieces rather than hanging from the wire.
Your Sennheisers have some advantages over the Bose, including their lightness. As for sound quality, well, if you disagree with CNET, fine. As long as you are happy that's all that matters.
Jun 2nd, 2006, 02:50 PM
#44
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Spread-spectrum or not, it's the same frequencies for both phones and jammers of phones. I don't recall GSM using spread-spectrum, though. You may be thinking of GPS. GPS, however, involves receivers only at the user end, and is thus harmless (but also easy to jam, and the jammers are extremely dangerous, since avionics often depend on GPS).
Jun 2nd, 2006, 03:21 PM
#45
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<b>xyz123</b>,
you keep on insisting that mobile phones will not work over the ponds, and it's simply not true.
No need for towers. The system has been tested and it's ready to go, but FAA is still witholding approval to use it until public hearings are concluded. They are accepting any and all comments from the public, organizational or individual. If you are against it, please write FAA.
The system would work of a satelite, not towers. Do some Googling.....
you keep on insisting that mobile phones will not work over the ponds, and it's simply not true.
No need for towers. The system has been tested and it's ready to go, but FAA is still witholding approval to use it until public hearings are concluded. They are accepting any and all comments from the public, organizational or individual. If you are against it, please write FAA.
The system would work of a satelite, not towers. Do some Googling.....
Jun 2nd, 2006, 03:25 PM
#46
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www.wikipedia.com:
<i>A few U.S. airlines have announced plans ([4] and [5]) to allow mobile phones to be used on aircraft, pending approval by the FCC and the FAA. The idea is similar to that used in some cars on the German ICE train: the aircraft will contain a mobile signal repeater that will then transmit the signals to a terrestrial-based system on separate frequencies that do not interfere with the cellular system. Since the repeater is literally right next to the passengers, the phones' output power would be reduced to the lowest level possible, reducing interference with cells on the ground. ARINC and Telenor have formed a joint venture [[6]] company to offer such a service on-board commercial aircraft and will be launching a service in late 2006 that will safely allow you to use your cellphone on-board the aircraft. The cellphone calls are routed via the on-board SATCOM to the ground network and an on-board EMI screening system stops the cellphones contacting the ground network.</i>
<i>A few U.S. airlines have announced plans ([4] and [5]) to allow mobile phones to be used on aircraft, pending approval by the FCC and the FAA. The idea is similar to that used in some cars on the German ICE train: the aircraft will contain a mobile signal repeater that will then transmit the signals to a terrestrial-based system on separate frequencies that do not interfere with the cellular system. Since the repeater is literally right next to the passengers, the phones' output power would be reduced to the lowest level possible, reducing interference with cells on the ground. ARINC and Telenor have formed a joint venture [[6]] company to offer such a service on-board commercial aircraft and will be launching a service in late 2006 that will safely allow you to use your cellphone on-board the aircraft. The cellphone calls are routed via the on-board SATCOM to the ground network and an on-board EMI screening system stops the cellphones contacting the ground network.</i>
Jun 2nd, 2006, 03:38 PM
#47
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The ARINC/Telenor system uses Code Division Multiple Access so that people can use their North American handsets in airplanes.
CDMA is a spread-spectrum signaling technology.
Spread-spectrum signaling can only be jammed with broadband energy, since the jammer can't know the sequence.
CDMA is a spread-spectrum signaling technology.
Spread-spectrum signaling can only be jammed with broadband energy, since the jammer can't know the sequence.
Jun 2nd, 2006, 03:50 PM
#48
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Whatever system is used, jamming and normal transmission occupy the same frequency spectrum.
CDMA is not immune to jamming, as GPS local denial technologies demonstrate. However, CDMA isn't used in most of the world for cellphones, anyway; the world standard is GSM, which is multiplexed by time and frequency.
Jamming, though, can be "nice": a local transmitter can pretend to be a base station and simply refuse all calls, for example. Conversely, no form of jamming will prevent interference from individual phones trying to contact the network.
CDMA is not immune to jamming, as GPS local denial technologies demonstrate. However, CDMA isn't used in most of the world for cellphones, anyway; the world standard is GSM, which is multiplexed by time and frequency.
Jamming, though, can be "nice": a local transmitter can pretend to be a base station and simply refuse all calls, for example. Conversely, no form of jamming will prevent interference from individual phones trying to contact the network.
Jun 2nd, 2006, 03:57 PM
#49
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No.
Since the jammer doesn't know the spread-spectrum formula, he has to transmit broadband energy across the entire band in order to be sure of hitting the traffic he's trying to interfere with. Broadband energy is a mixture of many frequencies that generates sum and difference frequencies and sidebands that are typically far outside the band in question. These are the ones that would probably interfere with signaling within the aircraft systems.
CDMA (not GSM, regardless of its popularity) is the technology under discussion, because that's the one being contemplated by the carriers we're talking about.
Since the jammer doesn't know the spread-spectrum formula, he has to transmit broadband energy across the entire band in order to be sure of hitting the traffic he's trying to interfere with. Broadband energy is a mixture of many frequencies that generates sum and difference frequencies and sidebands that are typically far outside the band in question. These are the ones that would probably interfere with signaling within the aircraft systems.
CDMA (not GSM, regardless of its popularity) is the technology under discussion, because that's the one being contemplated by the carriers we're talking about.
Jun 2nd, 2006, 04:51 PM
#50
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I bow to all of your superior knowledge of cellular science. Being called a terrorist/commie sympathizer does chill the conversation a bit, but don't suppose I can expect the decencies of debate always to be respected in a public forum like this.
Those of us whose dreams of world domination center around thwarting peoples' natural right loudly to rehash clever things they said that day and what they had for dinner, inches away from people who are trying to sleep, must twirl our villainous moustaches and slink back to our caves.
Skipping ignorantly over the real possibility of a jammer, I never contemplated buying one, just hoped tomboy would be nearby with his/hers. Nor do I really want to spend $100-200 for a headphone I'd use only on my too-infrequent plane and train trips.
If the FAA is indeed accepting public comment, hooray!
Those of us whose dreams of world domination center around thwarting peoples' natural right loudly to rehash clever things they said that day and what they had for dinner, inches away from people who are trying to sleep, must twirl our villainous moustaches and slink back to our caves.
Skipping ignorantly over the real possibility of a jammer, I never contemplated buying one, just hoped tomboy would be nearby with his/hers. Nor do I really want to spend $100-200 for a headphone I'd use only on my too-infrequent plane and train trips.
If the FAA is indeed accepting public comment, hooray!
Jun 3rd, 2006, 12:37 AM
#52
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You don't need to spread energy throughout the spectrum, you just need to interfere with the more limited use of the spectrum by the devices you want to jam.
Anyway, I've heard a lot more opposition to cellphones in the air than support. An important group that is opposed to the idea is composed of mainly business executives who value their time away from the phone aboard an aircraft; apparently it is the only place left where many of them are unreachable. I don't understand why they just don't turn their cellphones off if they want peace and quiet, but perhaps some Sacred Trust or contractual clause requires them to always have an operating cellphone on their persons (?).
Anyway, I've heard a lot more opposition to cellphones in the air than support. An important group that is opposed to the idea is composed of mainly business executives who value their time away from the phone aboard an aircraft; apparently it is the only place left where many of them are unreachable. I don't understand why they just don't turn their cellphones off if they want peace and quiet, but perhaps some Sacred Trust or contractual clause requires them to always have an operating cellphone on their persons (?).
Jun 3rd, 2006, 01:38 AM
#53
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This is getting more and more bizarre. Why does it have to be a choice between cellphones and jamming devices? Why not let the airlines know your concerns instead? If there is as much opposition to cellphone use on airplanes among the general public as on this thread, then the airlines wouldn't dare introduce the service.
There are many cases where a flight has been diverted to the nearest airport because of a drunk or bellicose passenger, with police waiting to arrest the culprit. My guess is, the same thing would happen to someone caught using a jamming device on an airplane.
There are many cases where a flight has been diverted to the nearest airport because of a drunk or bellicose passenger, with police waiting to arrest the culprit. My guess is, the same thing would happen to someone caught using a jamming device on an airplane.
Jun 3rd, 2006, 02:01 AM
#54
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>Sennheisers are vastly superior.
I thought that too. The one I bought in the early eighties worked well until last year when I bought a HD600. Very diappointing! After a few days the fist one had some low frequency resonance. On the 2nd one now after only 15 months one speaker failed. Crap made in Ireland!
I thought that too. The one I bought in the early eighties worked well until last year when I bought a HD600. Very diappointing! After a few days the fist one had some low frequency resonance. On the 2nd one now after only 15 months one speaker failed. Crap made in Ireland!
Jun 3rd, 2006, 02:51 AM
#55
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Headphones:
The best pair I EVER owned and I tried just about all the ones mentioned earlier -
Sony's MDR-NC11A
Great sound, decent noise cancelling and the size can't be beat if you travel a great deal. Highly recommend. They're not cheap, but worth every penny.
I have had this unit for ~2 years now and it works flawlessly, but since I'm going to Japan next week I may upgrade. The Sony megastore I visited last month in Tokyo had some newer models that sounded out of this world.
The best pair I EVER owned and I tried just about all the ones mentioned earlier -
Sony's MDR-NC11A
Great sound, decent noise cancelling and the size can't be beat if you travel a great deal. Highly recommend. They're not cheap, but worth every penny.
I have had this unit for ~2 years now and it works flawlessly, but since I'm going to Japan next week I may upgrade. The Sony megastore I visited last month in Tokyo had some newer models that sounded out of this world.
Jun 3rd, 2006, 06:09 AM
#56
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AAFF - You have to get yourself a pair of Shures. The sound quality of the MDR-NC11A is so crappy compared to the old NC10 I first couldn't believe it at first. [Well, now my dad uses it on the plane - the NC circuit is helpful there.]
I really think the Shures are perfect for travel. They are very small (almost disappear in my ear), very light, well built with robust wires, and a nice travel case. Besides the various fit sleeves, it also come with an attenuator which will be useful if you fly AF's 773 (audio output too high even at lowest setting), and the 1/2 plug (for your CX flights). The only thing missing is a two-to-one prong airline adapter, so you need to keep the Sony one or get a Radio Shack.
I really think the Shures are perfect for travel. They are very small (almost disappear in my ear), very light, well built with robust wires, and a nice travel case. Besides the various fit sleeves, it also come with an attenuator which will be useful if you fly AF's 773 (audio output too high even at lowest setting), and the 1/2 plug (for your CX flights). The only thing missing is a two-to-one prong airline adapter, so you need to keep the Sony one or get a Radio Shack.
Jun 3rd, 2006, 01:35 PM
#57
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<b>rkkwan</b>,
on this issue we will have to disagree. I would not trade my Sonys for anything.
2 years ago I shopped and compared in HK and for my ear the Sony product was and still is the best.
I will try other models again next week in Japan, but I probably will end up buying the lates Sony product again if I buy anything because as I said, the headphones are still great and there is really no reason to upgrade at the moment.
BTW, I mostly use my headphones with the iBook to listen to music/watch DVDs.
on this issue we will have to disagree. I would not trade my Sonys for anything.
2 years ago I shopped and compared in HK and for my ear the Sony product was and still is the best.
I will try other models again next week in Japan, but I probably will end up buying the lates Sony product again if I buy anything because as I said, the headphones are still great and there is really no reason to upgrade at the moment.
BTW, I mostly use my headphones with the iBook to listen to music/watch DVDs.
Jun 3rd, 2006, 03:12 PM
#58
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"You don't need to spread energy throughout the spectrum, you just need to interfere with the more limited use of the spectrum by the devices you want to jam."
Anthony, I can only explain this. I can't understand it for you. Spread-spectrum signaling takes the energy from a source and spreads it all over a band. In order to interfere with it in the manner you suggest, a jammer would have to spread his jamming signal the same way in order to "hit" wherever the legitimate signal is at any instant.
But that's impossible unless he has a duplicate of the legitimate transmission equipment that can replicate the direct sequence or frequency hops implemented in the legitimate channel, as the case may be. Absent a copy of that equipment, he has to resort to blasting energy all over the band spark-gap style, and that's where the danger of sum-and-difference beats aliasing into critical systems comes into play.
Anthony, I can only explain this. I can't understand it for you. Spread-spectrum signaling takes the energy from a source and spreads it all over a band. In order to interfere with it in the manner you suggest, a jammer would have to spread his jamming signal the same way in order to "hit" wherever the legitimate signal is at any instant.
But that's impossible unless he has a duplicate of the legitimate transmission equipment that can replicate the direct sequence or frequency hops implemented in the legitimate channel, as the case may be. Absent a copy of that equipment, he has to resort to blasting energy all over the band spark-gap style, and that's where the danger of sum-and-difference beats aliasing into critical systems comes into play.
