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time from cell phone was Re: [TowerTalk] Magnetic North Info & Map

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Subject: time from cell phone was Re: [TowerTalk] Magnetic North Info & Map
From: (Jim Lux)
Date: Wed Feb 12 12:58:13 2003
Indeed, while the various TDMA cell phone systems use GPS clocks for sync 
(such as the Z3801s you see available surplus), I don't know that the 
average phone actually gets a time message.  Certainly, my cell phone, a 
Cingular GSM from Motorola, does NOT get time messages, because the time 
displayed drifts substantially over a month.  There might be some option to 
make the displayed time match the "system time", but I haven't found it in 
the menus.

Given the large drift, I assume that the timekeeping function in the phone 
is run from the usual 32 kHz crystal. After all, it has to still "keep 
time", even when there is no cell site in view (like in the screen room at 

I think that the cell site/handset timing is all controlled by the cell 
site (which would make the handset cheaper), and they need to sync cell 
sites with each other to make it work properly.

At 12:26 PM 2/12/2003 -0500, you wrote:
>      An alternative to your shack's PC clock (which is probably not visible
>out by the tower's shadow) is a typical cellphone.  All digital cellular/PCS
>networks rely on GPS signals to maintain synchronization among the
>transmitters at the cell sites and the mobile handsets.  Most, if not all,
>handsets these days include a time display that is better than most you can
>find in a portable form factor, relying on the GPS signals for the correct
>73 de
>Gene Smar  AD3F

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