#79351 - 12/07/06 02:34 PM
Followup on the James Kim thread: Cell phone ping.
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Addict
Registered: 11/26/04
Posts: 514
Loc: S.E. Pennsylvania
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Can anyone expand on this? As I understand it, their cell phone was not able to be used to make a call because it was out of range of a tower, but a tower did get a 'ping.' What's the story?
Would a makeshift wire extension on the cell phone have extended its range?
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Univ of Saigon 68
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#79352 - 12/07/06 04:44 PM
Re: Followup on the James Kim thread: Cell phone p
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Enthusiast
Registered: 09/05/01
Posts: 384
Loc: Colorado Springs, CO
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Cell phones generally send out data ever so often (ever few seconds, I believe) that says "I am here." This is to let the cell towers know where the cell is. What happens in a city is that the phone will ping, and the surrounding cell towers will listen and compare notes. The phone is then instructed to communicate with the strongest (clostest) tower.
In this case, it would appear that one single ping was able to, by chance, get through. But it was not reliable enough to get a conversation going.
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-- Darwin was wrong -- I'm still alive
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#79353 - 12/07/06 08:51 PM
Re: Followup on the James Kim thread: Cell phone p
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Old Hand
Registered: 11/26/06
Posts: 724
Loc: Sterling, Virginia, United Sta...
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This also reminds me of Doug's advice that during a widespread disaster, you my not be able to have a voice conversation, but a text message will still go through.
I've never tried this myself, but perhaps one could attempt to send a text message in these circumstances. Perhaps some cellphones are actually smart enough to keep retrying until they get a good enough signal to send through the entire databurst.
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“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin
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#79354 - 12/07/06 09:43 PM
Re: Followup on the James Kim thread: Cell phone p
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Geezer
Registered: 06/02/06
Posts: 5357
Loc: SOCAL
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This also reminds me of Doug's advice that during a widespread disaster, you my not be able to have a voice conversation, but a text message will still go through. But who do you send it to? I called two dispatch centers (county and state) and neither could accept a 911 text message. . .dohh. So if a 911 dispatch can't handle text, who do you send it to? My intent is to send it to a relative out of state who can then call 911 for me on a land line.
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Better is the Enemy of Good Enough. Okay, what’s your point??
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#79355 - 12/07/06 09:46 PM
Re: Followup on the James Kim thread: Cell phone ping.
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dedicated member
Registered: 11/22/05
Posts: 125
Loc: SW Missouri / SE Wisconsin
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Don't know about the wire but I do know that climbing to higher ground helps a lot.
Jon
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#79356 - 12/07/06 10:09 PM
Re: Followup on the James Kim thread: Cell phone p
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Old Hand
Registered: 11/26/06
Posts: 724
Loc: Sterling, Virginia, United Sta...
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That would be my plan as well. Text message a relative or friend with a sit-rep, a location, and instructions then wait to see if it ever goes through.
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“Hiking is just walking where it’s okay to pee. Sometimes old people hike by mistake.” — Demitri Martin
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#79357 - 12/08/06 04:22 AM
Re: Followup on the James Kim thread: Cell phone p
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Cranky Geek
Carpal Tunnel
Registered: 09/08/05
Posts: 4642
Loc: Vermont
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The cell tower's controller also looks at your signal strength. If it isn't high enough, it decides you aren't worth it's time because you are too far away and according to it's programming, you probably have another tower near you that can actually pick up the signal. I wasn't aware of them logging that, though, so I'm suprised by that (happily).
As for extending the antenna, that would improve your ability to receive, but transmitting, with the power levels of a cell phone, I don't know. I doubt it, because you are putting out less than a watt IIRC.
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-IronRaven
When a man dare not speak without malice for fear of giving insult, that is when truth starts to die. Truth is the truest freedom.
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#79358 - 12/08/06 05:13 AM
Re: Followup on the James Kim thread: Cell phone p
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Member
Registered: 04/09/06
Posts: 105
Loc: Richardson, TX
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Let me expound a bit on Ironraven's msg. In any digital system, your phone is transmitting all the time, talking to the cells it can hear, and helping determine which is the best cell to talk to.
This information is also used by the network to figure out where calls to your phone need to be routed. Otherwise, calls to you from an external number would never be delivered to you. In your network, there's a server called an HLR, or home location register. This is a database that holds all of your network and account information. When you leave your home network and move to another network, your local information is stored in a VLR, or visitor location register. The interaction between the HLR and VLR are used to figure out how to get a call to you.
This stuff is updated all the time, but ordinarily nobody would be looking at it. The carrier would have to have the engineering staff draw logs from the VLR database (probably manually), figure out what sector on what cell on what switch that was, then go get the radio propagation maps to figure out what that cell and sector was covering. Then they'd know where to look.
An external antenna is absolutely a help. Antenna gain is the same whether you are transmitting or receiving, and every 6dB of gain gives you a doubling in range.
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John Beadles, N5OOM Richardson, TX
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#79359 - 12/08/06 07:23 AM
Re: Followup on the James Kim thread: Cell phone ping.
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Carpal Tunnel
Registered: 11/09/06
Posts: 2851
Loc: La-USA
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Cell phones use UHF frequencies. UHF is line of sight. The higher your altitude, the greater range of your line of sight. You can go to any C.B. shop (usually located near truck stops) and find adapters for most cell phones & external antennas. You can also find co-axial extensions in the 10' & 20' lengths to get your antenna up to a higher altitude while you stay on the ground.
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QMC, USCG (Ret) The best luck is what you make yourself!
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#79360 - 12/08/06 01:52 PM
Re: Followup on the James Kim thread: Cell phone ping.
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"Be Prepared"
Pooh-Bah
Registered: 06/26/04
Posts: 2210
Loc: NE Wisconsin
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My understanding was that they identified the cell that had the last known contact with their cell phone and used that location for the start of the search area.
A friend at work used to work for Motorola, and he said that the only way to get a ping from their cell phone would have been to fly a helicopter below the ridgeline to avoid other cell phone traffic at a distance, and then to listen for the individual ping of the cell phone with a higly directional antenna. Once detected, they'd need to get the ping in at least two other locations in an attempt to triangulate the location of the source (the car).
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