[aprssig] Dayton meltdown.

Rick Green rtg at aapsc.com
Mon May 23 10:56:03 EDT 2005

On Mon, 23 May 2005, Wes Johnston wrote:

> No..... it's like a passive repeater.  You take an active (ie preamp'ed)
> antenna on the roof and plug a passive antenna into it.
> Robert Bruninga wrote:
>> But then everyone gets the same position, the
>> position of the antenna on the roof.
   GPS units work on the timing differential between the signals received 
from multiple satellites.  With a repeater, active or passive, you receive 
the signals from the various satellites at a single point, the 
roof-mounted antenna. No matter where or how you repeat these signalls, 
their timing relationship WRT each other is fixed, so all GPS receivers 
listening to the repeated signals will report the position of the 
repeater's receiving antenna.
   It's really no different than a GPS receiver with an external antenna. 
No matter how you move the receiver, the position reported is that of the 
antenna.  Think of a repeater as a piece of 'wireless coax'.

Rick Green

"They that can give up essential liberty to obtain a little
  temporary safety, deserve neither liberty nor safety."
                                   -Benjamin Franklin
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