[aprssig] I almost understand WIDEn-N

[Keith VE7GDH]

Joe NE3R wrote...

> Yeah, it is lonely, but more lonely when your TNC doesn't seem to work
> (detects data carrier, but nothing displays in the terminal), but 
> that is another story.

Take the APRS client out of the picture and get the TNC going in a plain-
jane terminal program. Then go back to the APRS client when you know what 
settings to use. You can always do a hard reset on the TNC and then just go 
through and adjust the settings that need to be changed, unless your APRS 
client will enter all of those settings for you once you get the two of them 
talking to each other.

> I think I get it, basically the little n doesn't really do anything.

That's about it. It's really part of the alias... e.g. in WIDE2-2 
the "WIDE2" is the alias and the "-2" is an SSID, but with a special purpose 
as it gets decremented as it passes through a digipeater. Typically, 
the "WIDEn" will show how many hops you wanted to get. The second "-N" shows 
how many hops are left. It would be (very) bad practise to have n be a 
greater value than N.

> It looks like WIDE2-2 is the way to go for a fixed station, would 
> that be fine for mobile too?  In the mid west, especiallly to the 
> north, there dont' seem to be do many digis.  My summer 2009 
> vacation plans have me driving out I80 or I90, I thought APRS might 
> be a neat add on to that trip.

For many fixed stations, a path of WIDE2-1 would be "all they would need" if 
they can be heard by a high elevation digi with a large footprint. WIDE2-2 
is the "recommended" path for home stations, but if you know what is around 
you, you should be able to determine if the two hops is overkill or not.

Mobile stations could use WIDE2-2 but if things like terrain or the concrete 
jungle blocked their signal from getting to a WIDEn-N digi, they could get 
help from a "fill-in" WIDE1-1 digi that responds to WIDE1-1 and nothing 
else. The beauty of it is if both a WIDE1-1 dig and a WIDEn-N digi hear the 
beacon, they will both digipeat the beacon. If you are only heard by the 
WIDE1-1 digi, it will get passed on to the WIDEn-N digi with the "WIDE1-1" 
decremented to WIDE1-0 and thus used up, and the WIDEn-N digi will carry on 
and give you one more hop. If you are heard directly by the WIDEn-N digi, it 
will act on the WIDE1-1 and the next WIDEn-N digi down the road will act on 
the WIDE2-1 and use it up. It's a win-win situation.

> I'd also like see how we can use APRS for local emergency
> communications and short message traffic, somehow, I've found myself
> as an ARES AEC in my county.

APRS fits in very nicely with emergency communications. APRS objects can be 
used to show fixed assets like the EOC, reception center, location of a 
search manager and so on, and mobile assets like a vehicle can use a GPS to 
keep their position constantly updated, and of course, APRS messages can be 
sent between stations as well. Information from APRS weather stations can 
also show useful information. There are many ways APRS can be used in 
emergency communications. The more people you get involved with APRS in the 
ARES group, the better they will know how to put it to good use.

> And last but not least, APRS tracking would be a great service to the
> Mountain Club of Maryland during their biannual hike accross MD..

A perfect use for APRS. Once they see it in action, they will think of other 
ways to enhance keeping track of what is taking place out on the trail.

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