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[aprssig] WIDEn-N 'Decay Sequence'

VE7GDH ve7gdh at rac.ca
Mon Jun 19 14:48:33 UTC 2006


Anders (callsign?) wrote...

> "Can someone describe how the WIDEn-N knows when to stop?"

It stops when N gets to zero. e.g. WIDE1-1 wants to be digipeated by a
digipeater using an alias of WIDE1 and the SSID (the 1 on the end) gets
decremented to zero after it has been digipeated. Going back a step, if a
station beacons with a path of WIDE3-3, it will get digipeated three times
if it is

1) heard by a WIDEn-N digpeater in which case it will leave that digi with a
path of WIDE3-2
2) if that digi is in turn heard by another WIDEn-N digi, will go out the
other side as WIDE3-1
3) if that digi is in turn heard by yet another WIDEn-N digi, will go out
the other side as WIDE3-0 (the zero won't be shown just like yourcallsign-0
would just show up as yourcallsign.

> I'm guessing that when the packet is re-transmitted, the
> server software changes the text of what goes out. For example:
>
> Original transmission: abcdeWIDE2-2figk
> First retransmission:  abcdeWIDE1-2figk
> 2nd retransmission:    abcdeWIDE0-2figk

Not quite... the WIDE2-2 would leave the first digi as WIDE2-1. The second
digi would decrement it to WIDE2-0 and that would be the end of the road.

> and the next person that received it sees
> "Ahh, zero, don't rebroadcast."

Right... when the N on the end decrements to zero, it stops there.

> But if that's the case, the "-2" doesn't really do anything.
> Also, if the 'n' got decreased each time, I
> don't know why a user would specify "WIDE1-1, WIDE2-1", since
> the second entry would 'override' the first.

Hopefully some of that is already explained above, but... The reason for the
WIDE1-1 is so that it will hopefully be digipeated by a WIDEn-N digi, but if
it isn't heard by try WIDEn-N digi and it is heard by a "home fill-in digi"
that responds to WIDE1-1. If the original beacon is heard by BOTH a "home
fill-in" digi and a higher elevation WIDEn-N digi, they will both transmit
at the same time. Being a higher elevation and possibly with a higher gain
antenna and maybe running 10 watts (e.g.) instead of the 5 watts that the
"home fill-in" digi is running, the next WIDEn-N digi down the road (FM
capture effect) hears the WIDEn-N digi. For other stations near the station
that is beaconing, the WIDE1-1 (home fill-in) digi and the WIDEn-N digi,
they get two chances to hear the beacon... either direct, or from one of the
two digis depending on (FM capture effect) if one of the digis is stronger
at this other stations location.

Digi paths are used sequentially. e.g. if you used a path of VE7XYZ,WIDE2-2
and he digi VE7XYZ didn't hear you, any WIDEn-N digipeaters in the vicinity
would just ignore it. Only if VE7XYZ hears the beacon and digipeats it will
a WIDEn-N digi that can hear VE7XYZ respond to it.

> So that points to me not understanding how this works. *grin*
>
> Could someone show me the decay sequences for:
> "WIDE2-2"
> "WIDE2-1"
> "WIDE1-1"
> "WIDE1-1, WIDE2-1"
>
> Or perhaps a definition of what the 'n' and 'N' variables
> are named?

WIDE1-1 should NEVER be used after WIDEn-N. Scenario... a WIDEn-N digi at
1,000' above the valley will perhaps 20 WIDE1-1 digis around it down in the
valley, and 10 miles away, another WIDEn-N digi at 5000' with perhaps 100
WIDE1-1 digis within range of it. If a path of WIDE2-2,WIDE1-1 was used, the
digi at 1000' would respond to the WIDE2-2. It would go out the other side
as WIDE2-1 and the second WIDEn-N digi would respond to it with the WIDE2-2
now decremented to WIDE2-0. Doing its duty, it would send it out as WIDE1-1
and perhaps 120 home fill-in digis (as well as any other WIDEn-N digis off
on the horizon) would respond ALL AT THE SAME TIME. Result... lots of QRM.

Definition... WIDE3, WIDE2, WIDE1 etc. are aliases. In WIDE2-2, the last
number an SSID. When no SSID is specified, the SSID is zero, but isn't
shown... e.g. VE7GDH-0 is the same as VE7GDH. When a series of WIDEn-N
digipeaters digipeat a beacon, they decrements the N until each "hop" is
used up.

> Patience with me please, I got my D700 last week and only
> really finished the installation yesterday. Now that
all the hardware is straightened out, I'm looking at
the software subtleties . :)

Nice radio! Set the callsign to yourcallsign-7 for the SSID and set the path
to WIDE1-1,WIDE2-1 and you should be off to a good start! Run the radio at 5
or 10 Watts most of the time. Only crank the power up if you are out in the
boonies. Decide what is a reasonable rate to beacon at depending on your
speed (or if you are stationary!) and how busy the frequency is.

Read up on "voice alert" and get that set up. It involves enabling CTCSS on
144.390 so you transmit a 100 Hz tone when you beacon. The idea is that if
other mobile stations also have 100 Hz CTCSS, they will hear a packet burst
when you beacon. One of you makes a quick voice call with your callsign and
"QSY 652" or whatever frequency you want to move to and the other station
hears the callsign & frequency and you get to have a voice QSO on the D700s
other band while you are in range of each other... or QSY to a repeater if
available to stretch it out a bit. You should only beacon with the 100 Hz
tone enabled when you are actually there and listening.

Just read WA2MCT Mark's reply before hitting send. Lots of good stuff in
there. Jus one thing to add... I agree with Mark that APRS is supposed to be
local. I gave an example of WIDE3-3 above. There are some occasions /
locations where you will need / want more than two hops, but as of about a
year and a half ago, two hops has become the recommendation. For most home
stations, a path of WIDE2-2 should be used. Depending on location, you will
probably do OK with a path of WIDE2-2 while mobile. However, when using
WIDE1-1,WIDE2-1 you get the best of both worlds. Two hops whether you are
heard by a home fill-in digi first and then a WIDEn-N digi or whether you
are heard direct by the WIDEn-N digi. If it's the latter, your beacon will
go out a bit further. Using WIDE1-1,WIDE2-1 will tend to keep your beacon
more local. It is the universal and recommended path in North America. You
can also specify a particular digi, but as soon as you move away from home,
you would have to change the path. You can also use e.g. WA7-7 (if you were
in Washington) for state flooding to go out a maximum of 7 hops. This would
be an unusual situation where you needed to send a bulletin out further than
it would normally go.

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





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