[RFI] Fw: cell phone interference on airplanes

Jim P jvpoll at dallas.net
Wed Mar 1 23:35:59 EST 2006

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

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 seconds.

Jim P //  WB5WPA  //

----- Original Message ----- 
From: "Ed -K0iL" <eedwards at tconl.com>
To: <rfi at contesting.com>
Sent: Wednesday, March 01, 2006 10:02 PM
Subject: Re: [RFI] Fw: cell phone interference on airplanes

> 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 //
> ----- Original Message -----
> From: <W3DMB>
> >
> > Which means if all those cell phones on Flight 93 had been off - the USA
> > would now be missing the US capitol building (and many members of
> Congress).
> > Jerry
> > W3DMB
> >
> > In a message dated 3/1/06 12:06:38 P.M. Eastern Standard Time,
> > n0rq writes:
> >
> > I hadn't  seen this mentioned, and thought it interesting...
> > Carnegie Mellon  engineers have found that cell phones and
> > other devices on an airplane can  indeed cause interference
> > to the operation of the plane.  Details  at
> > http://www.post-gazette.com/pg/06060/662669.stm

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