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[aprssig] Help with Interfacing a GPSto Kantronics KPC-3

Scott Miller scott at opentrac.org
Wed Jan 3 23:25:19 UTC 2007


I think this is really my main objection to the proportional pathing scheme.
Even up the coast here, you don't need more than 2 hops to get all over.
There's really not much benefit unless you want to be seen in Arizona.  And
users who don't understand it are probably more likely to crank their rate
up higher when they don't see their packets getting in as often as they
expect.  Even with SmartBeaconing I have to remind users that when they're
sitting still, bench testing a unit, it's going to have a low transmit rate.
 
Scott
N1VG


  _____  

From: aprssig-bounces at lists.tapr.org [mailto:aprssig-bounces at lists.tapr.org]
On Behalf Of Stephen H. Smith
Sent: Wednesday, January 03, 2007 3:11 PM
To: bruninga at usna.edu; TAPR APRS Mailing List
Subject: Re: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3


bruninga at usna.edu wrote: 

The transmitting of raw NMEA strings over the air... 

... is highly discouraged in California.  Raw NMEA 

... occupy up to TEN times more air time than the 

most compact encoding format for APRS (Mic-E).

    



A little caution and explanation with that advice...



1) True, it is 10 times longer, but when you include the packet

overhead this is more like only a factor of 2 longer.



2) The KPC-3+ TNC tracker that sends raw NMEA can actually

produce less QRM, because it can be set to PROPORTIONAL PATHING.



  



This accomplishes nothing in Southern California where all the digipeaters
enforce SINGLE HOP no matter what path is set into the tracker.   All you
are doing is transmitting longer packets that:

1)  Occupy more air time

2)  Are much more likely to get trashed due to congestion on the saturated
channel here.  



--

Stephen H. Smith    wa8lmf (at) aol.com 
EchoLink Node:      14400    [Think bottom of the 2M band]
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"APRS 101"  Explanation of APRS Path Selection & Digipeating 
  http://wa8lmf.net/DigiPaths 

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