On Thu, Apr 29, 2010 at 8:30 AM, [email protected] <[email protected]>wrote:
> > > Thanks Keith and Lynn: > > I'll read that info > > If I set the 3 hop path, does it ALWAYS go three or will it stop as soon as > it hits an I Gate? > > I thought it stops when it hits the IGate. > > Or, if it gets to multiples, and some are digi's, will they keep it going > out to the path max? > > Curt > > Curt, I guess to answer this in part, one has to realize that the APRS system is a dual-layer system -- an RF layer and the APRS-IS (internet) layer. Once your packet gets into the APRS-IS via an Igate, any additional reports (duplicates) of that packet are removed by the APRS-IS core servers. This is the reason that you cannot see any additional path usage on the RF side once your packet is 'gated'. The RF layer, for the most part, is not aware of any packets already gated to the APRS-IS. Thus, if you have a 3 hop path, and you are in an area where the 3 hop path can be fulfilled, your packet will go thru 3 different hops. Please note, this does not necessarily mean 3 different digipeaters. This means 3 different relays of your packet expanding outward in all directions! Since your in Novi, I'll give a local example ( I'm up near Utica ). If you bring up aprs.fi and center it on Southfield, MI, then expand out the map to see Lansing to the west, you will see the following digi's that I will use as examples. W8FSM-3 in Southfield K1DE-5 near Milford ( W of FSM-3 ) WF5X-13 in Utica ( NE of FSM-3 ) AB8XL in Brandon ( N of FSM-3 ) W8FSM-5 near Holly ( NW of FSM-3 ) W8FSM-4 in Lansing VE3KCR in Chatham/Kent Now, you send a posit from Novi using a WIDE1-1,WIDE2-2 path in SE Michigan, you can have all the possible routes happen: W8FSM-3,WF5X-3,VE3KCR ( your packet made it to Central Southwest Ontario ) W8FSM-3,AB8XL,W8FSM-5 ( your packet made it to Flint area ) W8FSM-3,K1DE-5,W8FSM-4 ( your packet made it to Lansing area ) Only the original relay thru W8FSM-3 a single hop. All the other packets ( all six of them! ) are relays of the original first digi. All of that coverage above happened with ONE posit. Now, if your path had only been WIDE1-1,WIDE2-1, you can remove the last three calls from the list, and you can see that you just halved the amount of traffic created on the RF part of the APRS system -- plus removing a large chunk of Michigan and Ontario that aren't in immediate need of seeing your position. Generally, along major interstate routes, you will never be outside of accessing an Igate for very long using a WIDE1-1,WIDE2-1 path. Hope the example helps. 73, Randy WF5X
