On Fri, Aug 14, 2009 at 11:53 AM, Broncus<[email protected]> wrote:
>> If you use a path such as WIDE1-1,WIDE2-1,MYCAR and have your vehicle >> set to preemptive digipeat on MYCAR, it will be handled by the car, >> but will look like this after. WIDE1-1,WIDE2-1,MYCAR* where the >> asterisk (*) represents the has been digipeated bit. Any subsequent >> digipeater fill-in or mountaintop will only look for a path that is >> after the has been digipeated bit. > > I don't quite get this. But I think you are saying, the car would see > the MYCAR (fromthe HT) and forward the beacon with the > WIDE1-1,WIDE2-1 intact which a fill-in or WIDE digi would see > and treat it like it came direct. No, exactly the opposite. The outgoing path in a packet HAS to be used in the order it is listed. Using WIDE1-1,WIDE2-1 means that WIDE1-1 has to be used before WIDE2-1. WIDE1-1 is supported in home fill-in digipeaters, as well as the main WIDE area digipeaters, so any digipeater will respond to that path. Once WIDE1-1 is used (and marked with the has-been-digipeated bit which sometimes is shown as the call of the digipeater followed by an asterisk "*"), then only a WIDE area digipeater will act upon the WIDE2-1. If you use a named path such as PNDRVL,WIDE2-1, and you are not heard by PNRDVL first, you will not get digipeated by anyone else. With preemptive digipeating, (which is only supported by Scott's OT2 as far as I know), it will scan all of the aliases in the outgoing path, and if it finds an alias which it is configured to act upon in a preemptive manner, it will use that alias up. So if the path is as above, WIDE1-1,WIDE2-1,MYCAR, and you have the OT2 set to act preemptively upon MYCAR, then the OT2 would be able to digipeat the packet even if the packet was heard directly, and neither the WIDE1-1, nor the WIDE2-1 had been used up already. If the MYCAR alias is acted upon, the packet would end up looking like it had been completely used up even though it hadn't been acted upon by a fill-in nor a WIDE area digipeater. It's a little bit of a strange concept. It was based on the idea of having a fully mobile self deployed network in support of a Search And Rescue event. Each SAR team would carry an OT2 set up as a preemptive digipeater set to act upon the SARn-N alias. Each SAR package would use an outgoing path of WIDE1-1,WIDE2-1,SAR7-7. This would allow those heard by the regular APRS-RF network to be digipeated normally. If however the SAR teams ended up in an area with no APRS infrastructure in place, the teams would become their own self deploying, self digipeating network, which would hopefully be able to get tracking information back to the search HQ. Even in an area of digipeater coverage, the SAR network would digipeat itself. There would be no flooding effect to the local network as the SAR alias is not regularly supported by the main digipeaters. Make any sense? James VE6SRV
