Arte Booten, N2ZRC
As with any
packet networking, path selection depends on what can be heard
by you and those that can actually hear you. You can get the equivalent
of an MHEARD command, showing you the paths stations near you
are using and which stations you hear direct by pressing the D(igipeat)
key. See who these are. Hopefully, one of them will be a WIDE.
network relies on the majority of fixed stations having their
TNC's DIGIpeat function turned on and their MYAlias set to RELAY.
Since APRS is an unconnected protocol, packet nodes (with a few
exceptions), which rely on connections and error-checking for
data transfer, are counterproductive. APRS utilizes that DIGIpeat
function by the use of GENERIC callsigns as a TNC's alias(es),
most commonly RELAY and WIDE.
various flavors of WIDE, all represented differently on the screens
of different APRS versions. But first let me describe the function
of RELAY in the APRS network, as this is a useful, but often
misused, generic callsign. RELAY stations generally consist of
your average "Joe Aperze" in order to allow low-power,
low gain mobile and portable stations into the network. In many
areas, most of these RELAYs are able to hit the nearest WIDE directly.
that if you can hear and get digi'd by the nearest WIDE from a
fixed location with reasonable consistency, you should AVOID THE
USE OF RELAY because if a WIDE hears you, others probably can
as well..and they're probably also using the alias RELAY. This
causes collisions as each of the RELAYs that hear you try to digipeat
your packet at about the same instant. And your packet will probably
die then and there.
to the various flavors of WIDE. The first is just that. It'll
digipeat anything that specifically goes via its callsign as well
as to the generic callsign WIDE, shown as a small green star in
APRSDos. Sometimes, there's also a weather station associated
with this DIGI, in which case APRSDos shows them as a green circle.
Next comes WIDE-RELAY. These are TNC's that can have two aliases
and digi packets addressed via RELAY, WIDE or its own callsign
and show on APRSDos as big green stars.
We also use
WIDEs that use an alias of TRACE. Their firmware supports the
DIGI-SWAP function. When it DIGIs something addressed via one
of its generic callsigns it changes that GENERIC callsign to that
of its own in the VIA: field of that packet. This allows people
to see how the network is propagating and makes selection of paths
a bit easier. Those of us running APRSDos, WinMacAPRS and pocketAPRS
see these as that large star with a T in the middle.
type uses something the inventor of APRS (The Great Oracle of
Glen Burnie) Bob Bruninga, WB4APR, first proposed several years
ago to enhance unconnected networking via amateur packet radio
and Kantronics recently picked up on. It uses a scheme Bob calls
WIDEn-n. "N" is a number between 1 & 6. The first
of these would represent the number of "hops" you want
of these numbers depends on how many times that packet has been
digipeated by the time the last digi retransmitted it. It's set
by the firmware in current Kantronics TNC's (but I understand
that others *MAY* be coming out with it in the "near"
future) and decrements one from that number on the packet it's
heard, but hasn't yet DIGI'd. WIDEn-n TNC's can also be set for
callsign substitution, as I described above. They have an N in
the middle of the green star.
of WIDEn-n is seen best in a network in which most, if not all,
WIDEs in a given area have such firmware. In others, users of
callsign substitution might consider shutting that feature off.
Unfortunately, not everybody that has a digi is USING Kantronics'
stuff. And some of those that are aren't willing or able to change
the chip. This pretty much describes the APRS network in my part
of the woods.
best path? Look around. Who hears you. Who do they hear. And where
do you want the packets to go? I suppose you'd like a nice, stable
path from Montauk to Albany and Newark to Binghampton. Good luck.
The path you need is there, if you can see anybody else on your
screen. If a Green Star can hear you, then that's gonna be your
starting point. From there, just follow the bouncing green stars.
Booten (firstname.lastname@example.org) AEC for Digital Services, NYC ARES/RACES|
|Riverdale, New York [FN30bu] !4052.71N/07354.06WNPHG5370/A=00240|
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