[aprssig] RE: SDG-9 pass by Annapolis plot 2

Robert Bruninga bruninga at usna.edu
Fri Mar 21 19:28:14 EDT 2008

Balloon watchers...

OK, here is plot 2.  In order to get 12 dB of signal change over
1 hour, on a very stable and completely unwavering signal, the
path length to Annapolis would have had to change by a factor of
4 in one hour.  This plot suggests to me that it went closer to
Annapolis than the original predict.  See attached.

Ill let you guys that have a much better idea of speed take it
from here.  If you can match your better estimates of speed to a
factor of 4 change in range north and east of Annapolis over one
hour, then you can improve this wild guess.  You could also them
make different assumptions about my "6dB estimates" however and
probably get quite other answers...

Its this kind of signal strength visualization that can be such
a powerful direction finding technique on APRS and Ham radio..
Ill eventually add this experience to the APRS Dfing web page:


Bob, WB4APR 

> -----Original Message-----
> From: Robert Bruninga [mailto:bruninga at usna.edu] 
> Sent: Friday, March 21, 2008 7:05 PM
> To: bruninga at usna.edu; 'Robert Rochte'; 'Balloon_Sked'; 
> 'Ralph Wallio, W0RPK'; 'Pierre Thomson'; 'Bill Brown'; 'Joe'; 
> 'Phil Manor'; 'Mike Manes'
> Cc: 'TAPR APRS Mailing List'
> Subject: RE: SDG-9 pass by Annapolis plot 1
> > Drawing concentric rings that are a factor of 4 in 
> > range combined with other data, should be able to 
> > give a rough fix...?
> I can't resist leaving that undone...  Attached is an attempt
> put my data on the predicted plot.  It is easy to see that it
> does not match.  To get this 18 dB or so of signal strength
> change in just an hour and 20 minutes from my location means
> must have been going extremely fast ... -OR- passed a lot
> to me than this predict shows.  Ill work on that in my next
> email...
> Bob, WB4APR
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