[aprssig] Appalachian Trail APRS trip report
vo1one at gmail.com
Wed Mar 8 12:16:01 CST 2006
On 3/8/06, Andre PE1RDW <aprs at pe1rdw.demon.nl> wrote:
> Stephen H. Smith schreef:
> > scott at opentrac.org wrote:
> >>>6) Cell phones didnt (though we were getting full
> >>> scale signal readings (maybe we were hitting too
> >>> many cells?
> >>My experience (usually on a boat off the California coast) seems to be that the cell towers are easily heard by the phone way out there, but not vice versa.
> > Typical -- (Relatively) high-power base station talkout v.s.
> > flea-powered battery-limited talkback from mobile (hand-held cellphone).
> > [ I'm forever trying to convince my girl friend that I can't hear her
> > cell phone decently, even though she hears me clearly from the
> > wireline side, when she calls on it from inside the house. ]
> The GSM system like it used in europe is better matched, it also alows
> the tower to controll the mobile´s output power (most of the time the
> handheld will be in the 10mW range)
> If you can recieve the tower then the tower can recieve you, no exception.
Not necessarily. If you are greater than 35km away from a GSM cell
site, you can have a strong signal from them, but you will not be able
to obtain a time slot. Aircell (if they're even still around) was a
cellular phone service available for aviation used AMPS because it
wasn't dependant on having time dependant slots to operate and could
be used effectively for a couple hundred km's depending on altitude,
etc. CDMA is also limited, I think the figure is 57km. Still another
issue at high altitude is cell sites on the same frequency interfering
with each other. With digital, it's all or nothing. With AMPS, a
white noise laden interfered with signal is still usable, your call
has a better chance of getting through and you can adjust your
position for better reception.
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