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Re: REFLECTOR: cell phones through audio panel


I respect your electronic acumen but in this particular case (digital RF
datacom and telecom) I think you're wrong!  

I assume you already know that multiple local sites receive the comm and
selectively ignore it (only one "connects") even with cellphones, but
that you are referring to sites that are line-of-site in different
cities.  With AMPS-band (cellphone) service, this can be a problem since
"local area" is defined in isolated areas, and (as you state) one site
from each isolated local area may respond (although I doubt it would
ever result in multiple billing - only one could connect to the
destination, if it were even possible to complete a call with the
collisions going on).  

However, with PCS (wideband at 1800-2100 MHz, not sure if this applies
to narrowband PCS in the 800-900 MHz band, usually used for analog
cellphones) - it was explained to me that this is not a problem for the
following reasons:

1) With PCS, there are no isolated areas, the digital negotiation is
"known" across the entire digital PCS network and only one site will
"connect", even if several cities "hear" it.
2) Typically, only one city (or two, near the hand-off point) will even
hear the comm.  With PCS, the ground station negotiates the signal
strength with the handheld unit, and will command it to reduce power
until it is just good enough to carry on communications with the
connected site.

A more major problem would be the spotty coverage - line of sight is
true but you won't get reliable communication if you're 50 miles (more
or less - this is just a guess) away from the nearest ground antenna.

Also, at typical airliner speeds of 400 kts plus, I wonder if the ground
sites can keep up.  But at 100-200 kts, I'd think it really isn't a

-john rourke

HadleyAir@aol.com wrote:
> It is all still line of sight, John, and once you are airborne any tower
> within RF range will work the call. Multiple billing may occur with the
> activation of multiple sites.
> Martin