> Would someone in the know explain why technically the cell phones in the
> headrest(Verizon?) Airphones don't cause the same problems as customer
> owned cell phones.
Two words: "Proper engineering"
1) Proper placement of T and R antennas on the outside of the fuselage
2) Control of and proper freq spacing and inter-transmitter isolation
with filter and or isolators on the transmitters used for the air-to-ground
link.
3) Choice of frequency bands that do not conflict with COMM or NAV receivers
> Why are they immune from causing RFI to the aircraft
See answer above.
> Why are they immune from causing RFI ...
> ... massive interference to cell sites below?
The GTE Airfone system has enjoyed their own exclusive assigned set
of frequencies for such systems. There is one system that is an
exception to that rule, we can discuss that later.
(Isn't Google working anymore?)
"In the mid-1980s commercial mobile telephony took to
the air. The North American terrestrial system or NATS
was introduced by Airfone in 1984, the company soon
bought out by GTE."
MORE:
http://www.privateline.com/PCS/history10.htm
And I have a beef now too.
It centers around the word 'cell' in cell phone which is short for
'cellular' phone which was really formally known as AMPS in
the industry (Advanced Mobile Phone System) to contrast it
with the several predecesor mobile phone systems such as
IMTS (Improved Mobile Telephone Service) previously fielded
by Bell and other private carriers known as RCCs (Radio
Comon Carriers) which included a lot of mom and pop
operators in the smaller cities.
Radio Common Carrier history:
http://www.wirelessweek.com/article/CA153848.html?spacedesc=News
Jim P // WB5WPA //
----- Original Message -----
From: "WX5L" <wx5l@charter.net>
To: <dswenson@wearne.net>; "RFI" <rfi@contesting.com>
Sent: Thursday, March 02, 2006 7:05 PM
Subject: Re: [RFI] Fw: cell phone interference on airplanes
> Would someone in the know explain why technically the cell phones in the
> headrest(Verizon?) Airphones don't cause the same problems as customer
owned
> cell phones. Why are they immune from causing RFI to the aircraft and also
> from causing massive interference to cell sites below?
>
> Thanks,
>
> Randy
> WX5L
>
>
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