[RFI] Fw: cell phone interference on airplanes

Ed -K0iL eedwards at tconl.com
Thu Mar 2 21:59:26 EST 2006


You're getting very Pedantic again.  :-)

I think everything you say is probably correct, but mostly applies to
Metropolitan areas with short towers located close together, not in rural
areas with taller towers farther apart.  And the plane was flying very, very
low as well.  As Mr. Swenson pointed out, it would depend on the system's
rural design as to how it might work or not work.  Some cell phones were
shown as inoperable by the "writers" while verified accounts of relatives
calling a cell phone on the plane and getting thru were shown that way as
well.  They showed the calls as very short calls ending abruptly, which all
agrees with what you say below.  Mark Bingham's mom got thru to him only to
lose him less than a minute later.  Then she left a chilling message on his
phone mail telling him to take over the plane if at all possible.  This
message was played on two of the documentaries.

I'm not going to call the victims' relatives a bunch of liars.  They all
acted heroic that day.  But you go right ahead because it really doesn't
matter, does it?  

-----Original Message-----
From: Jim P 

> Network, and Discovery Channel) showed at least two passengers who 
> used their cell phones at various times: Tom Burnett and Mark Bingham.  

I don't believe it.

This is the continued making of another pernicious urban legend IMNSHO.
The popular account of these events ALWAYS cites 'cell phones'. Balderdash.

I don't and won't buy it based again, on the careful scrutiny and listening
and subtle clues in the wire, newspaper and televised interviews that I used
to determine what it was they actually used.

Coupled with the fact that it would be a difficult if not nearly impossible
to hold ANY call from a jet aircraft for more than a minute or so.

Let's take a minute to discuss the nature of a 'cell site':
o Cell sites are tri-sectored affairs, with 'neighbor' cells
  look into the adjacent coverage area of their neighbors.
o Calls are meant to be moved from neighbor to neighbor.
o Calls will not HAND OFF to a cell for which a neighbor
  cell has NOT been assigned/designated as a potential
  candidate or neighbor cell, no mattter how 'real' some
  docu-drama would make you believe, therefore, calls
  will NOT handoff across a system.
o Handoffs/handoff initiation takes place in a finite, usually
   per-cell site determined period of time. Set this interval
   too low and the switch load goes up. Set it too long
   and it's possible to 'drag' through a suitable neighbor
   cell without performing a handoff; those kinds of call
   usually drop.
o  Cell sites also many times employ antennas with either
   physical or mechanical  'downtilt'. These have 'lobes'
   and nulls that can exend into small areas above and
   around the cell site, further poluting the airspace above
   cell sites/a cell site system.
o Cell site TDMA (like IS-136 and GSM) ALSO have to
   do TIME ALIGNMENT to keep their subscribers in
   their assigned time slot (NO FAIR transmitting in adjoining
   time slots!), this VARIES with distance and one could
   conceivably outrun the MTSO switch's ability to keep
    phones in their time slots were they airborn. (CDMA may
    have an advantage here, I don't know.)
This is just plain, straight-away falls in the category of 'make believe'
when one KNOWS the technology involved and physics and other elements that
come into play.

416 channels  (one set each for A and B band carriers) used over and over
requires a LOT of careful, sectorized planning JUST to make a cellular
system PLAY well at ground level. And how many dropped calls and noisy calls
and cross talk does the average caller experience using a cell phone?

Multiply that by 1000 if you are in the air.
That would make it prety near near impossible to do and a genuine fluke if a
call managed to get 'set up' and the circuit maintained for more than 20

Jim P //  WB5WPA  //

----- Original Message -----
From: "Ed -K0iL" 

> On the three docu-dramas/documentaries I've seen (History Channel, A&E
> Network, and Discovery Channel) showed at least two passengers who used
> their cell phones at various times: Tom Burnett and Mark Bingham.  Tom's
> wife and Mark's mother both mentioned talking to them on their cell
> Although one program shows Mark's initial call was on the GTE phone while
> the other shows him on a cell phone.  So there is some conflicting info.
> There were one or two others shown using or trying to use cell phones as
> well.  And the GTE phones were also shown being used at different times by
> various passengers, but according to one of the programs, only 8 GTE
> could be used at a time so many of the others tried to use their cell
> phones.
> So there are, in fact, accounts of cell phones being used confirmed by
> relatives of the victims.  They apparently worked intermittantly so the
> calls were the longer calls like that Todd Beamer had with Ms. Jefferson.
>  -de ed K0iL
> -----Original Message-----
> From: Jim P
> GTE Verizon that morning reports that **23 calls** were made from Flight
> that morning via their Airfones. Not ONE news account or interview of
> personally involved told stories on TV and elsewhere that indicated 'cell
> phones' were used. I could verify *no* accounts that morning or afterward
> where a terrestially-based 'cellular'
> phone was used. Not one.
> Jim P // WB5WPA //

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