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[aprssig] Appalachian Trial Golden Packet!

Bob Bruninga bruninga at usna.edu
Sun Mar 15 03:57:40 UTC 2009


> Imagine getting an APRS packet all 
> 2000 miles from one end of the Appalachian 
> Trail to the Other!... in about 40 hops...

Well, got out the trail maps with my son this evening, and it was immediately apparent that the strategy must be to ZIG/ZAG between mountain ranges rather than trying to shoot straight along the AT range.    Since the AT is straight along the ridgeline, then, the height of average terrain between the peaks is only a few hundred feet difference, limiting line of sight distances only in the 20's of miles.

But by zig/zagging from one mountain range to another, we can take advantage of THOUSANDs of feet difference in heights above average terrain between peaks across valleys and should be able to get  much much farther per hop.

BUT, this second-order knowledge cannnot be easily derived from just the AT maps, it requires input from local sources who know the highest Peaks +/- 50 miles from the AT, and those are probably the VHF contesters and REPEATER owners...

So this is going to be a good cross polination of ham radio enclaves... to ut together the best plan.

Anyway, I have an idea for the numbering scheme.  We number the peaks per state from North to SOuth.  So the full hops from Maine to Georgia might look like this when abbreviated:

M12N12S12N123J12P12345D1V12345678C1234T12345G1

M is the start in Maine
N ofr New Hempshire
S for Mass
N for newyork
J for new jersey
P for PA
D for maryland
V for VA
C for North Carolina
T for tennessee
G for Georgia.

Stations along the way would use tactical calls like MASS-1, MASS-2, MASS-3 for the three peaks through Massachusetts.  Each station along the way should be able to see their 7 nearest neighbors north and south, or 15 stations total.  With a  beacon rate of 5 minutes each, that would mean an average QRM rate of only one packet every 20 seconds.  Maybe this will allow the golden packets plenty of room to get through. (remember, we are on our own frequency (maybe 145.01?)

Of course, most of those packets will be LONG ones, because they can be carrying as many as 7 Traced callsigns in each packet...  That's 65 bytes of just callsigns.  But then when a golden packet is re-initiated after 7 hops, then that trace history is abbreviated back down to just 8 or 9 bytes using the naming convention above.

In fact, we can limit our re-initiating to say 5 hops or less, so that we can STUFF the abbreviation into an unused DIGI field so that it is carried along for the ride, and does not have to corrupt the original golden packet DATA.

If the two end-to-end golden packets do get through, then we can propogate a PHASE-2 operating mode, where stations are encouraged to then re-initiate the two packets from their two farthest DX stations further along the trail.  This then could potentially get an end-to-end packet from every participating station!

And of course, most of these paths can be checked out in advance, since there are probablly APRS digipeaters on a lot of these peaks already...

Bob, WB4APR

>We would use the TEMPn-N digipeating that should be built into every D700 (or other portable digi). see www.aprs.org/TEMPn-N.html .
>
>We would have to operate on something OTHER THAN 144.39, but maybe 145.01 would do.  Also we would NOT operate on the same weekend as any other SOTA acticity, since we would be shooting ourselves in the foot with RF blocking from the same hilltops.
>
>The plan might be something like this:
>
>1) All AT stations operate with TEMP7-7
>2) This lets you see your 7 adjacent nodes in both directions
>3) Being linear, there will be few dupes
>4) Most stations can be just D700's acting as digis (or other temporary digi that can support TEMPn-N digipeating.
>5) At each site along the way, you watch for a "golden" packet from either end (Springer Mountain or Katadin).  Then you do the following:
>(a) you  capture it and save it for record purposes, 
>(b) you re-INITIATE a packet from your station that regenerates the packet with your new TEMP7-7 path, but it includes a shorthand notation of all successful hops so far.
>(c) The above regenerated packet will go both ways, so the 7 statiuons prior can also see that it has been picked up and forwarded along the way.
>
>If that becomes too much congestion, then we might ask that when a packet is "regenerated", that the sending station has to change its path to DIGI1,DIGI2,DIGI3,TEMP4-4 to force it to only go the preferrred way.
>
>Also we dont want all 40 statiosn to be regenerating the golden packets.  Just the stations about every 7 hops or so.
>In this respect, maybe we should designate the regenerating statiosn beforehand so that we can enforce it.
>
>This way the packet can go the needed 40 to 50 hops, yet still maintain a record of the hops.  We will need to come up with 1and2-LETTER abbreviations for all peaks along the way, so that we can keep the final packet under 80 bytes!
>
>Then we set aside a weekend and go do it!  We might need to schedule two weekends, one for the first attempt, and the second one for all of us that screw it up the first time...
>
>If you are interested in gettting involved in the planning and activation of this, please join the peak2peak group on yahoo groups...  But we will distinguish this specific event as the AT Golden Packet event.  Anyone know of any high-PR dates for the AT that might  be appropriate?
>
>Again, I only saw the tip of the iceberg today when I saw a note on SOTA, and I hope I am not jumping the gun and jumping into someone else's project.  But I sure get excited when it comes to playing PACKET.  And this is the ultimate... packet...
>
>Need people with good RF and mountain top experience to help organize and plan out the HOPS.  I bet, on our own freq, we can probably even average 100 mile paths if we really do it right.  That would only take 20 hops...
>
>I'll certainly volunteer to plan the Maryland hop...
>
>Bob, Wb4APR
>
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