[aprssig] Balloon DFing on APRS (DFS)

[Gregg Wonderly]

On Mar 5, 2012, at 12:29 PM, Bob Bruninga wrote:

>> I believe Bob is planning to use the original directional DF, 
>> not the omni-DFS for his balloon tracking. 
> 
> Lynn, good assumption.  Launch is not today (obviously) but now can be
> Friday or the next week...
> 
> But I'd love to use OMNI-DFS since we should get plenty of signal only
> reports and it would be ideal to see them as well.  But because we did not
> anticipate balloon Signal Strengthing, the OMNI-DF technique only makes
> meaningful plots for reasonable PHG values since the size of a OMNI-report
> is based on the PHG plot.
> 
> Im racing to meet a travel deadline and will be out the rest of the week.
> But Ill lay this at your feet... (if you want to consider it)...
> 
> Maybe we should look at extending DFS significantly for Balloons?  In fact,
> I think I have allowed (in my code anyway), the extension of the HEIGHT byte
> in PHG to extend beyond "9" (not sure if this is documented anywhere), but I
> cannot remember if we let "A,B,C,D,E,F" be the next heights or we let it
> just extend in the ASCII table above "9" as :;<=>.  Anyway, lets assume
> ABCDE?
> 
> A = 10,240'
> B = 20,480'
> C = 40,960'
> D = 81,920
> E =163,840

I'd suggest that we need to find a way to narrow the gap between these larger values.  The propagation ranges are very different between these values.  Can we make the letters each represent something smaller, like 5120 feet each.

95000/5000ish would be just 19 letters, and if we went to Z, we'd get to 130,000 feet where you get to the edge of what we'd consider a "mobile" APRS station.

Gregg Wonderly
W5GGW