[aprssig] WIDE settings

[Keith VE7GDH]

Ken K9FV wrote...

> Thank you Gary for such a good explanation of the settings.  Mobile
> stations should use both "WIDE" statement, and base stations should
> only use the single "WIDE" statement.

The recommended settings for mobile stations in North America are
WIDE1-1,WIDE2-1 for a two hop path. The recommended settings for fixed
stations is WIDE2-2 for a two hop path. In a FEW areas, a longer path might
be needed... a very few areas. Mobiles would then use WIDE1-1,WIDE2-2
instead. If a fixed station was within earshot of a "high" digi (one high
enough to have a very large footprint might want to consider a path of jus
WIDE2-1 for a one hop path. It just depends on the topography and location
of the adjacent digi(s) and IGates.

> The first "WIDE1-1" will allow 1 hop from "any digi". If this first
> digi does not get the packet to an IGate, then the second "WIDE2-1"
> will allow a second hop only if needed to find an IGate, but the max
> is 2 hops with this setting - is this correct?

You're getting there, but you need to understand a few subtleties. A path of
WIDE1-1 will be acted on by BOTH any home fill-in "WIDE1-1 only" digi and by
the "high WIDEn-N digis". It doesn't matter if a fill-in digi (typically at
someone's house and in a relatively low elevation) is triggered
simultaneously as a WIDEn-N digi. If only the WIDE1-1 digi hears the mobile
and gets it to a higher elevation WIDEn-N digi, that's great. If you are
digi'd by both a WIDE1-1 and a WIDEn-N digi at the same time, it doesn't
really matter. The transmission by the WIDEn-N digi possibly running 5-10W
into a gain antenna will be much stronger at the next WIDEn-N digi than the
one from the WIDE1-1 digi. The important thing is that the mobile station is
"helped" out by the WIDE1-1 digi if necessary. If a WIDEn-N digi hears the
mobile station direct, it WILL act on the WIDE1-1 and kick it out the other
side with the WIDE2-1 still intact to be acted on by the next WIDEn-N digi.
It doesn't matter if the mobile station is heard direct by an IGate, or if
it hears the WIDE1-1 digi, or if  hears the WIDEn-N digi... or if it hears
all three. I see that Bob replied with a very accurate statement that AX.25 
will process digipeater fields in sequence, but I already had the "long 
version" typed out. As a further explanation of that, you could use a path 
of DIGIME,WIDE1-1,WIDE2-1 and you would not get digipeated at all... unless 
there was a digi within earshot of you that responded to an alias of DIGIME. 
Again, the path is used sequentially.

> IF a mobile station with the "WIDE1-1,WIDE2-1" setting is heard by a
> "high digi" first, then there would only be a single hop because the
> "high digi" will ignore the first "WIDE1-1" and only act on the second
> "WIDE2-1" statement and allow only a single hop - is my understanding
> correct??

No. The "high digi" (the WIDEn-N digi) if it hears the mobile station direct
will act on the WIDE1-1 and kick it out the other side with the WIDE2-1
intact so that the next WIDEn-N digi will act on it.

> Then a mobile running WIDE1-1, WIDE2-2 could have a possible 3 hops,
> the first from any local "fill in digi".

That is correct, but keeping in mind that a WIDEn-N digi will act on the
WIDE1-1 if it hears the mobile station direct.

> The second WIDE2-2 will allow a "high digi"up to 2 hops (if needed)
> to reach an IGate.  Once the packet reaches an IGate, there are no further
> repeats of the packet.

You are correct that WIDE2-2 would give you two hops via "high" digis, but
the digi doesn't know or care if your beacon has made it to an IGate. You
could be heard direct by an IGate and that would have no bearing on how any
digis acted on the path that you were using.

> I think I understand the meaning of your term "high digi" (major
> digi?) vs "fill in digi" - In as I said, I'm just learning this stuff
> so I am not familiar with the old RELAY setting).  A "high digi" is a
> digi that has a large coverage area, while a "fill in digi" is more
> like a home station setup to digi, and would have a much smaller
> coverage area.

Typically, the WIDEn-N digis are located at a higher elevation than the
surrounding area. In some areas (e.g. Colorado) they might be at 10,000
feet. With the digis far apart and very little APRS activity, that is fine.
If you stuck a digi at 10,000 feet in a plane above Los Angeles or
Baltimore, it would be a disaster. In high density areas, digis should be
"high enough" but not too high.

Typically, a WIDE1-1 fill-in digi is at someone's house. Even a mobile
station could be set up as a WIDE1-1 digi, but probably not too many are set
up that way. Someone living on a mountaintop should probably not set up a
WIDE1-1 only digi. If a digi was needed there, it should be a WIDEn-N digi.
If it is surrounded by WIDEn-N digis on top of every hill around it, an
extra digi just wouldn't be needed.

The old RELAY is obsolete and shouldn't be used. There was no callsign
substitution and no dupe suppression, leading to a ping-pong effect. RELAY,
WIDE, TRACE and TRACEn-N are obsolete in North America. Most digis (I hope
that is accurate) have updated their settings. A few have not yet. A few may
never get updated. The operators of those digis are doing the APRS users a
dis-service by encouraging the uses of obsolete settings and all of the
problems that came with them.

> The settings for these digi's depend on the station owner to
> correctly set the parameters of his station depending on the
> coverage area each digi is expected to have. (am I correct here?)

Yes. www.nwaprs.info is a good site to look at suggested settings written in
plain and easy to understand language. It is up to every digi operator to
set it up properly and to use the suggested settings. APRS is a cooperative
thing. Doing things the "right" makes it work better. Doing it the "wrong"
way with improper settings makes APRS less useful and less useable. Also,
take a look at www.ew.usna.edu/~bruninga/aprs/fix14439.html, but ignore the
obsolete graphic 3/4 of the way down the page... WIDEn-N filtering at
borders with the white background that says "all digis support RELAY, WIDE"
etc. I'm sure Bob didn't intend to leave it there, and it will eventually be
replaced with something that reflects currently accepted settings.

> When looking at an APRS map, sometimes I see a solid green star - that
> is a "fill in digi" and the green star with the yellow "D" is
> considered a "high digi"???

The symbol used by any APRS station should as accurately as possible denote
what kind of station it is. Digis use a star. The overlay helps tell users
what kind of digi it is. The beacon comment can provide more information.
Typically, a star symbol with an L overlay would indicate that it doesn't
support SSn-N (state flooding... with SS replaced with the two letter
abbreviation for the state or province), S would indicate that it DOES
support SSn-N, and 1 (one) would indicate that it was a WIDE1-1 only digi. I
don't know what the "D" is. You can view a list of symbols
www.ew.usna.edu/~bruninga/aprs/symbolsX.txt and there is some overlay
information at www.ew.usna.edu/~bruninga/aprs/symbols-overlays.txt. I
couldn't find the "D" so perhaps someone else could answer that. What is the
callsign of a digi that is showing a "yellow D" on your map? There is also a
chart at www.wa8lmf.net/miscinfo/APRS_Symbol_Chart.pdf that shows symbols...
e.g. #/ would be a star with a D in it, but it would possibly be an "old"
digi using obsolete settings. #\ would be a numbered digi that would allow
the "S" to be added for a digi that would support SSn-n.

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