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[aprssig] ALOHA Circle on findU and/or APRSWorld

Steve Dimse k4hg at tapr.org
Mon Nov 1 03:03:34 UTC 2004

On 10/31/04 at 8:52 PM Christensen, Eric <CHRISTENSENE at MAIL.ECU.EDU> sent:

>Is it possible to view the 40 closest stations that are on RF (i.e. no
>Winlink, CW, or just IS stations) listed?  That way people could tell
>what kind of path to use if they weren't using APRSdos?  I like the way
>findU shows the closest stations but it shows both IS and RF stations.
>Maybe it could be done using the Q-construct or the presence of an
>I-Gate in the path?  Not sure if it can be done with the current code.

Not with findU's current code, and furthermore this is much harder to do than it
appears at first glance. Positions arrive at findU by many different routes,
there is no single test you could perform on a packet to tell which originated
on RF, so the code would be complex, and in a few cases it may not be possible
at all. Worse is the problem of IGates and others on both RF and INet...in most
cases client programs transmit on both RF and INet at the same time, so the INet
packet is the one that makes it onto the APRS-IS and therefore findU. These
would be eliminated from the list, even though they appear on RF. 

I don't believe it is possible to generate the info you ask for reliably with
findU. The reason is the same one I always give whenever a propagation question
is posed for findU and the APRS-IS. These systems were designed to transport the
data; the dup-checking and other characteristics of the system preclude their
being used for any propagation studies.

Steve K4HG

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