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Cellular Phone Forum / Providers / Verizon / May 2004Mile high signals
The question is simple: has anyone received a signal from a commercial airliner 6 miles high, for more than 10 seconds? Particularly an all digital signal. Comments how the signal that high in the sky and in a tin can is? > The question is simple: has anyone received a signal from a commercial > airliner 6 miles high, for more than 10 seconds? Particularly an all digital > signal. > > Comments how the signal that high in the sky and in a tin can is? I frequently fly on a private aircraft and lose a signal somewhere between 10,000 and 15,000 feet. Larry > The question is simple: has anyone received a signal from a commercial > airliner 6 miles high, for more than 10 seconds? Particularly an all digital > signal. > > Comments how the signal that high in the sky and in a tin can is? It doesn't matter. If you're flying 200-500 miles per hour you won't be able to acquire a tower and hold on to its signal for more than a second anyhow.  SignatureJustThe.net Internet & New Media Services, Apple Valley, CA PGP: 0xE3AE35ED Steven J. Sobol, Geek In Charge / 888.480.4NET (4638) / sjsobol@JustThe.net Domain Names, $9.95/yr, 24x7 service: http://DomainNames.JustThe.net/ "someone once called me a sofa, but i didn't feel compelled to rush out and buy slip covers." -adam brower * Hiroshima '45, Chernobyl '86, Windows 98/2000/2003 > It doesn't matter. If you're flying 200-500 miles per hour you won't > be able to acquire a tower and hold on to its signal for more than a second > anyhow. But the radio horizon is massively expanded at 35,000 feet. And path loss is greatly diminished. W/ completely unobstructed line-of-sight, a signal w/ a Rician distribution (i.e. a dominant LOS path) will attenuate 6 dB for every doubling of path distance. As such, the signal attenuation at 128 miles from a BTS is only 6 dB greater than at 64 miles from the BTS...only 12 dB greater than at 32 miles...only 18 dB greater than at 16 miles...only 24 dB greater than at 8 miles... At cruising speed & altitude on commercial flights, I have acquired CDMA 1900 forward-link PNs from sites more than 100 miles distant. Of course, Ec/Io was heavily degraded -- too many uncorrelated distant sites corrupting orthogonality. And reverse-link power was insufficient to complete a network registration let alone originate an outgoing call. But, on the forward-link, individual PN offsets could be identified & the sync channel could be successfully decoded. On one particular hour-long flight, I logged Sprint PCS SIDs from the Chicago MTA, Minneapolis-St. Paul MTA, Des Moines MTA, St. Louis MTA, & Kansas City MTA. Of course, all of the above were conducted for educational &/or investigational purposes only... :) Andrew -- Andrew Shepherd cinema@ku.edu cinema@sprintpcs.com http://www.wirelesswavelength.com/ >> It doesn't matter. If you're flying 200-500 miles per hour you won't >> be able to acquire a tower and hold on to its signal for more than a second >> anyhow. > >But the radio horizon is massively expanded at 35,000 feet. And path >loss is greatly diminished. I subscribe to Alltel and have a Startac with the debug mode enabled. I flew with a friend in a 182 from Greenville SC (GMU) to Augusta GA several months back with it in debug mode. As we climbed (to 5500, I think), I watched the signal fall from -65dB to -115dB ... in view of 4 Alltel towers. I attribute that, perhaps wrongly, to a highly directional omnidirectional antenna <g>(pattern flat like a pancake or frisbee). I did not sync at all while in the air. As we approached the Augusta airport, signal strength come up, and I obtained sync as we were on final. He has Sprint; his experiences are similar, but he doesn't try to use it in the air .. something about "first, fly the airplane" >Of course, all of the above were conducted for educational &/or >investigational purposes only... :) > >Andrew Exactly the same .... I never tried to make a call. Had I, things may have changed. I do note that when roaming, I will often register with a different system after I hit "send". George I Don't have a clue what you just said. I thought using a cell phone on an airplane was not allowed? Dan >>> It doesn't matter. If you're flying 200-500 miles per hour you won't >>> be able to acquire a tower and hold on to its signal for more than a second [quoted text clipped - 28 lines] > >George > The question is simple: has anyone received a signal from a commercial > airliner 6 miles high, for more than 10 seconds? Particularly an all digital > signal. > > Comments how the signal that high in the sky and in a tin can is? As a pilot I can tell you, no. In addition to the many other fine answers you'll get telling you it's not possible (because of speed of aircraft, distance or such)...and not to mention it's currently illegal (at least in the states) - there's a technical reason as well: Most cell sites undoubtedly use some type of directional antenna (probably sectional or panel type, not beam type) to help reduce interference and boost the signal. While all antenna's bleed, they tend to have very sharp attenuation in the directions they are not pointed towards. Since most cell traffic is expected to be terrestial bound, they tend to be pointed at a down angle from the tower (i.e. pointed towards the cell phones below it) and thus there's not much signal escaping up. Sure, high frequency signals tend to "expand" as they traverse a certain distance - but undoubtedly the points at which you run through these apexs in a commercial airline are far an few between.... And even if they did use an omnidirectional antenna, again, the properties of such an atenna are that the signal is strong in the plane of the direction (so typically in some sort of donut shape around the vertical element) and attenuated perpendical to the plane (so no up and down signal). Now, an omnidirectional antenna on it's side might give a better signal - but that wouldn't be so useful to cell phones on the ground as now the polarization of the signal is wrong (so there'd be a severely diminished signal). > The question is simple: has anyone received a signal from a commercial > airliner 6 miles high, for more than 10 seconds? Particularly an all digital > signal. > > Comments how the signal that high in the sky and in a tin can is? |
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