Any cell phone experts out there? I suspect that cell phone signals are line-of-sight like most other radios.

If so, then boosting the power isn't the issue - it is the height of the antenna. The boost might help in marginal areas, but is no replacement for a PLB which can work anywhere in the world AND give your position even when you don't know what it is.

The celluar phone network is a complicated engineering challenge, and thus the equipment is designed to make assumptions on things to ensure efficiency of the network. The signals from cell phones are within the 800Mhz and 900Mhz ranges for the old analog types. The new PCS ones are in the 1.3Mhz range (I believe, they're over 1Ghz anyway). These signals are nearly exclusively line of sight. There is no bending, and in fact, these signals can be stopped by pine needles.

Boosting signals from a cell phone should be used with care, because of the nature of a cellular network. Cellular phone output wattage is limited so that the phone will only work so far from the tower. This is necessary with the design of a "cellular" network. The other factor is how 911 calls are handled. With most newer handsets, there is an entry programmed into your phone called "Emergency Number". When this number is dialed, the phone will handle this number differently. Instead of trying to work through your paid carrier, the phone may, connect you to the closest cellular tower, regardless of provider. Now you're probably thinking, but if I'm moving, how is the call transferred between competing carrier cell towers? Beats me, but 911 calls are supposed to be handled differently than all other calls, without regard to carrier, or subscriber status. This is why phones with no service can still dial 911. If you let your children play with powered non-subscribed cell phones, they could still initiate a call to 911.

So, getting to the point of the boosting option, that should definately only be used when you are NOT in a dense cellular network. Boosting your signal and dialing 911 may cause problems. Usually, if you are within the same network (say, Cingular), then the system will determine the best tower to receive your call from, and "ignore" any other "hits" your amplified cell phone makes with it's towers. If you have the amplifier and hit multiple towers on multiple providers, I don't believe there is any protocol on how to handle this case. There probably is, but I don't know about.

Like you said, the height of the antenna and line-of-sight to the receiver will make all the difference.

Another thing with cell phones, in the U.S. there is a move to "Phase II" cell phone 911 service. This service uses either the phone, towers, or a combination of both, to determine the locatio n of your cell phone. These will be displayed on a map in the 911 call center to show your location. Some areas don't have Phase II, and you should always give your cellular phone number and location you are calling from, as a cellular 911 call may not always be routed to the jurisdiction you are in.

I should also note that for the privacy concerned, a recent case of a bouncer murdering a young woman in NY pointed out that your cell phone "ping" signals are recorded AND STORED by cell phone carriers. A ping signal is a signal that lets the network know which tower the phone is closest too, so that calls to it can be routed quickly. It is possible that these signals are recorded from ALL towers your phone "pings" and thus, your location triangulated. I'm not a lawyer, but what scares me is that they could be used in civil cases, and not just criminal cases. If you're somewhere you don't want to be, then, perhaps you want to turn off your phone. <img src="/images/graemlins/smile.gif" alt="" />

That's all I know. And I'm not the expert.

I had heard many years ago that hitting multiple cell towers is one of the reasons why cellular calls from airplanes are not allowed (I think the other big safety reason being possible interference with the onboard avionics). At 30,000 feet, you can be line of sight to many towers at once. However, one thing that I never heard mentioned after 9/11 is the use of cell phones by the passengers on United 93 to call family and loved ones. I don't recall ever hearing any mention of reception problems. I have heard of problems with the onboard "air phones" during that incident but not with any cell phones. Perhaps a protocol had been developed by then?

I have a knock off of the Wilson cellular amp that I keep in my truck. It works alright, and has saved my bacon a few times. It doesn’t work miracles, but in areas where you were able to some times get just a blip of service every once and a while, you will get at least one bar of signal with the amp. Outside of areas like that it is hit or miss. I did get great service with it when I got my truck stuck in a canyon and was able to call for some friends to come and help, but on the other hand I still can’t get service on certain areas of the ranch that have a reasonably good path to the local cell tower.

I think I paid $175 for mine.

I belive that cell phones are "mostly" line-of-sight. If you are in a canyon, there is a posibility that the signal might hit some trees and bounce around enough to reach a tower. Of course, the signal loss is tremendous, but any signal is better than no signal.

Note that the Kim family had a ping recorded on a distant cell-phone tower. It is possible that a cell phone amplifier might have allowed them enough signal to send a text message.

Of course, if you are going to spend $400, you might as well get a PLB <img src="/images/graemlins/wink.gif" alt="" />

I'd like to hear more about the incident when a CB radio saved you.

Actually, the agency that banned use of cell phones on aircraft wasn't the Federal Aviation Administration(FAA)- it was the FCC. You're right, they'd hit a whole ton of towers, and in the early days of cell phones, it trashed the way they billed you, and they effectively couldn't.

I have no concrete proof as to this, except that it came from a guy who worked on avionics systems for a few major airlines (including flight testing) that a cell phone has never been proven to interfere with the avionics. When I'm out tooling around in my Piper Warrior, I'll be honest-I leave my phone on.

Not that I have anything fancy enough to get interfered with.... <img src="/images/graemlins/blush.gif" alt="" />
-Kyle

Cell phones and avionics was a Mythbuster's topic one time. I can't remember the details, but the testing initially showed cell phone signals possibly affecting a navigation instrument (a VOR thingamajigee?), but I can't recall if they had to crank up the signal strength beyond normal levels to achieve that. However, with further testing, they weren't able to affect any avionics.

Actually, since there's talk of allowing cell phone use on commercial aircraft, I guess the telecom companies have figured out how to deal with multiple hits to their system from the same phone.

Cell phones are going to be allowed to be used on planes in the near future? Thought I saw that on cnn.com

I remember that MythBusters episode. It was shown that many phones can interfere with VOR signals and make your OBI (Omni Bearing Indicator, for the non-pilots here) go wacky. These tests were done inside of a Faraday cage with completely unshielded avionics. When they attempted the same tests inside a parked business jet, the aircraft's shielding prevented the OBI from being affected.

However, keep in mind that the OBI is what guides an aircraft along the runway's localizer and glideslope (kind of like "autoland", for the non-pilots here) and you'll realize that final approach, 200 feet above runway level, with lousy visibility is the last place you'd want to have a darned cellphone start screwing with your gauges. Would you bet your butt on your aircraft's avionics shielding in that situation, or would you rather just have people shut the cellphones off?