Hi Steve,<br><br>That's what I was afraid of with the preempting concept.<br><br>I believe the hardware we're using supports alternative or proportional pathing so I'll give that a shot and set the airborne digi to only use SAR1-1 and see where that gets me.<br>
<br>Thank you for the reply!<br><br>Greg<br><br>NV6G<br>OpenAPRS.Net<br><br><div class="gmail_quote">On Mon, Sep 14, 2009 at 9:52 AM, Stephen H. Smith <span dir="ltr"><<a href="mailto:wa8lmf2@aol.com">wa8lmf2@aol.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
What do you mean by " if the airborne digi preempts, hitting on SAR1-1" ? <br>
Path hops are processed SEQUENTIALLY from left to right. Assuming you mean some kind of modified firmware that will let the airborne digi respond to "SAR1-1" out of sequence, even if the first two hops are not yet "used up", it will depend on how the path is retransmitted. If it comes out of the digi as: <br>
WIDE1-1,WIDE2-1,SAR1-1* <br>
then potentially dozens and dozens of digis on the ground over a radius of hundreds of miles will simultaneously respond to the "WIDE1-1" hop. [Both low-level home fill-ins AND true high-level WIDES respond to WIDE1-1.] Then all these retransmissions over a huge area will trigger all the real WIDEs again on the second (WIDE2-1) hop. <br>
If the airborne firmware traps and modifies the path string to output something like:<br>
<br>
WIDE1-1*,WIDE2-1*,SAR1-1* <br>
or chops off the first two hops entirely to output just<br>
<br>
SAR1-1* <br>
the airborne digi will, at least, not re-trigger the ground-based digis. However this STILL won't prevent ground-based digis from responding independently and simultaneously to the first two hops while the airborne digi is responding to the last hop. <br>
Further, on each digipeat by a ground-based digi, the airborne one will hear yet another "un-used" SAR1-1 and act on it again if the dupe table isn't big enough and dupe time isn't long enough. You will be creating huge numbers of simultaneous packets that will "step on each other" over a very large area. <br>
The disruption caused by "WIDE1-1,WIDE2-1" paths on balloons at altitude has been discussed many times on this list. The impact on the 144.39 network of a digipeater at altitude, rather than just a originating transmitter, will be at least an order of magnitude worse.<br>
<br>
<br>
<br>
If your user's devices could be set to alternately beacon on two different paths (i.e. the "proportional pathing" of the D710), and you set the airborne digi to respond exclusively to SAR1-1 only, the impact on 144.39 would be VASTLY reduced. The users would alternately beacon "WIDE1-1,WIDE2-1" (to utilize the terrestrial digipeater network only), and SAR1-1 (to utilize the airborne digi with a guaranteed single hop only). <br>
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