[aprssig] what is RELAY, WIDE, TRACE, etc?

[Keith - VE7GDH]

Jason KG4WSV wrote On 02/08/2004 7:57:13 AM

> Assuming I've got all that right, first question: what is the
> difference between RELAY and WIDE? As far as I can tell from the
> standpoint of an end user who is transmitting or receiving there is no
> difference: RELAY,RELAY; RELAY,WIDE; WIDE,RELAY; WIDE,WIDE; and WIDE2-2
> would all get me digipeated twice.  I assume what various digipeaters
> do with these may depend on what kind of digi it is and how it's configured?

I'll let someone else give you a more detailed reply on the other points you raised (it looks like you have a good handle on the source and destination addresses), but you should never have two "relays" in your unproto address. You don't want your beacon ping-ponging around between every RELAY station within earshot of the first one that heard you. You also never want to have RELAY after a WIDE. This would be even worse than just having two RELAYs. Presumably every RELAY within 100 KM or so of any WIDE digi that heard you would commence to digipeat your beacon and it would kill the entire system around you for a while.

A typical path would be RELAY,WIDE2-2. However, if there isn't a RELAY within earshot, your beacon ends there. Only those that could hear you directly would know of your existence. WIDE2-2 is pretty reasonable in populated areas. The first WIDEn-n digi to hear you would decrement the count to WIDE2-1 and send it on. The next WIDEn-n digi that heard it would decrement it to zero and no other WIDEn-n digis would digipeat your beacon. Typically, most WIDEn-n digis will also respond to RELAY, so theoretically, RELAY,WIDE2-2 will get you out 3 hops. In sparsely populated areas RELAY,WIDE3-3 or 4-4 or 5-5 probably wouldn't raise too many eyebrows. In areas where the APRS frequency is saturated and with well placed digis, more than 2-2 is just not necessary.

A path of RELAY,WIDE,WIDE should get out through a RELAY if one is within earshot, and if so, through two WIDE digis, but the WIDEn-n digis are smarter and there won't be as many duplicate packets with WIDEn-n. However, any "dumb" TNC could be set up as a RELAY or WIDE digi, but it would be better off as a RELAY digi somewhere in the fringe areas than it would be in an area that was already heavily used.

Again, I'll let someone else give you a "more proper" description of TRACE, but it is similar to WIDE except that every TRACE digi that it passes through would add it's callsign to what it sent out. You can look at a TRACE frame and see all the TRACE digis that it went through. A beacon that just went through a WIDE will just show you the last WIDE that it went through....e.g. this station was 429 km from me, but I know how his beacon got here... through MTHEBO, ELLIS, and SUMAS:

N7HQR-9>APRHH2,MTHEBO,ELLIS,SUMAS,TRACE2*,VE7GDH,I:=4458.51N/12400.49Wv000/000

I checked at findu.com and the actual unproto address looks like it was RELAY,TRACE2-2.

73 es cul - Keith VE7GDH
--
"I may be lost but I know exactly where I am"