[aprssig] Dayton meltdown.

[J. Lance Cotton]

Robert Bruninga wrote:
> Indoor GPS...
> 
> Yes, but everyone will still only be at the 
> location of the antenna on the roof, because
> that is where all the signals arrive at their
> given phases.  re-transmitting them inside
> the building is an equal delay to all signals,
> so all positions will all still only be the position
> of the antenna.  Bob, WB4APR

Or rather, people's locations will not be calculated accurately by the GPS 
receivers, but since there is additional non-constant delay from the 
re-transmitting antenna to each individual receiver.

By putting in a passive GPS repeater you have broken one of the assumptions 
that a receiver uses in the position calculations. Everyone will have a 
different position, but none will be correct/accurate.

-Lance KJ5O


>>>>Wes Johnston <aprs at kd4rdb.com> 5/23/2005 10:21:14 AM >>>
> 
> 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.  Bias the
> whole
> thing with 5v to run the preamp on the external antenna.  The passive
> antenna becomes a radiating antenna.  All the GPS signals become
> "mirrored" inside the building.  The only problem I can see is getting
> the coax thru the roof.  Think of it is cutting a hole in the roof so
> that your portable GPS unit inside the building could see the sky.
> 
> I liked the vicinity tracking, but as far as I know, it's only use was
> at dayton back in 1998 using those mfj data radios that were mod'ded
> to
> be really really deaf.
> 
> Wes
> 
> Robert Bruninga wrote:
> 
> 
>>>Also, has anyone in dayton ever considered a 
>>>GPS repeater in each hall? 
>>>   
>>>
>>
>>But then everyone gets the same position, the
>>position of the antenna on the roof.  
>>
>>My proposal for indoor tracking at Dayton is in 
>>"vicinity tracking" where we put nearly deaf low-power 
>>digis in each room.  With no change on the part of
>>the trackers, once indoors, they start getting reported
>>via the room digis and since we have full path
>>tracing, then the individual is located in the room
>>of the first digi that heard him.
>>
>>This was my plan back in 1998 or so.  Its all 
>>written up in my vicinity.txt file.  These digis are
>>called BOX-N digis and whever APRSdos sees
>>a packet that comes in via a "box-N digi" it
>>ignores the actual posit and plots it as a vicinity
>>plot in the vicniity (100 feet) of the box-N digi.
>>
>>de WB4APR, Bob
>> 
>>
> 
> 
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-- 
J. Lance Cotton, KJ5O
joe at lightningflash.net
http://kj5o.lightningflash.net
Three Step Plan: 1. Take over the world. 2. Get a lot of cookies. 3. Eat the 
cookies.