[aprssig] What I sent to N7HRT

[Earl Needham]

         After typing this up, I thought that it might be interesting here 
on the APRSSIG.  This was quite a bit of typing and thinking...

At 06:58 PM 1/9/2005, N7HRT at aol.com wrote:
>Earl,
>I was having trouble being heard last night, the closest digi is almost 
>100 miles from my current location.  I did not know if making the path 
>longer would bring any new hops, I was using 3; is that a more appropriate 
>number?  I have to confess that I am new to the whole APRS thing and some 
>of the parameters are a black hole of explanations.  I have seen a whole 
>range of stuff on WIDE and TRACE with no standard as I can see.
>
>Any input is appreciated.

         OK, Dave, maybe I can help a bit.

         First, a good path would probably be WIDE3-3.  That will get you 3 
hops in all directions, won't generate duplicate packets, will keep your 
range short, etc...

         Now to try and explain digipeating in APRS.

         WIDEn-N (like WIDE3-3) gets your signal repeated 3 hops in 
whatever direction it will go in.  Your signal will show  up like this:

 From your station:
N7HRT-6>APU25N,WIDE3-3:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         After 1 digi:
N7HRT-6>APU25N,WIDE3-2:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         After 2 digis:
N7HRT-6>APU25N,WIDE3-1:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         After 3 digis:
N7HRT-6>APU25N,WIDE3*:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         You can see the packet stays the same length throughout while 
keeping the same advantages as shown above.

         Now, TRACEn-N (like TRACE3-3) is different.  Check this out -- 
(I'm using DIGI1, DIGI2, and DIGI3 because I don't know the digis in your 
area) --

Direct from your station:
N7HRT-6>APU25N,TRACE3-3:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         After 1 digi:
N7HRT-6>APU25N,DIGI1*,TRACE3-2:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         After 2 digis:
N7HRT-6>APU25N,DIGI1,DIGI2*,TRACE3-1:=3637.70N/09937.10W-*EM06-Harper 
Co,Ok. N7HRT at arrl.net {UIV32N}

         After 3 digis:
N7HRT-6>APU25N,DIGI1,DIGI2,DIGI3*:=3637.70N/09937.10W-*EM06-Harper Co,Ok. 
N7HRT at arrl.net {UIV32N}

         And that all looks OK, but after SEVEN digis you might have the 
following:
N7HRT-6>APU25N,DIGI1,DIGI2,DIGI3,DIGI4,DIGI5,DIGI6,DIGI7*:=3637.70N/09937.10W-*EM06-Harper 
Co,Ok. N7HRT at arrl.net {UIV32N}

         The packet gets longer.  The TRACE function can be used to see 
what path a packet follows to get to a specified location, but should be 
used with care, as it will tend to clog the network.

         Generally, and more especially in areas where the network is 
mature, a path of 2 hops is about right, and any more than 3 is tending to 
be excessive.  Here in the southwest, we can "get away with it", because it 
can be a long way to the next APRS op, but when you get to a big city, look 
out!  They don't like it much.

         Hope this helps,
         Earl


Earl Needham, KD5XB, Clovis, New Mexico DM84jk
http://kd5xb-2.no-ip.info