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

Robert Bruninga bruninga at usna.edu
Thu Jan 4 14:43:07 CST 2007

>>>> Subject: RE: [aprssig] Help with Interfacing a GPSto
Kantronics KPC-3
> 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. 

I think you missunderstand.  Proportional pathing works
perfectly well for two hops.  And reduces packets on the channel
by a factor of 10, and overall channel loading by at least a
factor of 5 even in a 2 hop area.

> 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.  

I doubt it.  Why would they set porportional pathing if they did
not want to take advantage of it?  The advantage to them is
higher local rates and lower DX rates an dlwer QRM for everyone.

> ________________________________
>>> 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
>> 		overhead this is more like only a factor of 2
>> 2) The KPC-3+ TNC tracker that sends raw NMEA can actually
>> produce less QRM, because it can be set to PROPORTIONAL
> 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...

You are correct in this case.  I agree. NMEA trackers are less
efficient in an area such as the LA basin, where only 1 hop
packets are allowed.


More information about the aprssig mailing list