Order Tray | Contact Us | Home | SIG Lists

[aprssig] objects sent from a client (was Re: UIDIGI Setup)

Keith VE7GDH ve7gdh at rac.ca
Thu Nov 5 17:37:32 UTC 2009


Bob WB4APR wrote...

> Just to clarify.  That's not the point.

Ed isn't going to like this, but I did change the subject line.

> The point is for "info type" objects generated by "software
> driven" programs [at non-digi-locations]. The reasons these
> local info frequency objects are best generated at the digi are:

In my case, they are one and the same place. On the other hand some
stations generating an object could be so far down in a hole that they
wouldn't be heard at all unless they went through a digi.

> 1) Only the digi can hear the channel and avoid colliding with
> users

That could be re-worded to either "sometimes only the digi" or even
"often only the digi"... it's a bit misleading to make a blanket
statement and say "only the digi" can hear the channel.

I'm not on a mountain-top, but I am on a ridge about 165M ASL. I can
hear one mountain-top digi over 200 km away, and a few others not much
short of that, but that's because they are quite high. However, there's
mostly just water (and a few other islands) between me and there, and I
can hear a lot of traffic from the mainland and in other directions.
While I have mountains to the west and mountains to the east, there's a
lot that I can hear in between. Perhaps my location is somewhat unique,
but it can't be completely unique.

> 2) Only the digi can generate these packets direct over the
> coverage area

Correct, a digi can send a packet direct that can be heard over it's
coverage area. However, another station sending a packet with one hop
via that digi will have the same coverage, but it will take up two time
slots and stations very close to the originating station will  hear two
copies. However, in the case of an IRLP APRS object, the information
will be accurate and far more useless than a "here I am" kind of beacon
without conveying any other information. You could even look at is two
opportunities for mobile stations to hear the change in status of an
IRLP node, giving them a better chance of having the most up-to-date
information.

> 3) Home generated objects have to use 1 hop which collide with
> other users

Collisions are a part of APRS, but "home" stations don't necessarily
have to use any path at all. It's up to the operator to set the path
which could be direct or not. Obviously, if they are normally using any
path at all, they need to consider whether they are the right station to
generate any kind of information object.

> 4) Home objects usually use the station's set path, usually 2 hops

Usually, but not always. I think that more people would listen to your
suggestions if you weren't so rigid with blanket statements. At least
you used the world "usually" above instead of "always".

> 5) Anything beyond the local digi is SPAM and MISSINFORMATION

I would agree with the SPAM part in most cases, but it wouldn't be
misinformation. It would just be propagating it where it wasn't needed.
Umm... isn't MISSINFORMATION kind of like a hookers bulletin board?
What a difference one "s" makes - hi!

> Result is that the QRM and collision potential of these objects
> is 16 times greater when generated at a  home station than at
> the digi.  And all those unwanted copies are in areas where the
> object is useless SPAM. (A 2 hop path where most digis can hear
> 4 others = 16 dupes.

You are talking about objects going out with multiple hops. Yes, a
clue-less person could easily do that. Perhaps I put more faith in my
fellow ham, and perhaps you have seen more examples of people
"doing it wrong".

> Compared to ONE packet that is guaranteed not to collide with
> anything).

You and I know that isn't guaranteed, but a packet sent from a high digi
would have less chance of collisions because it at least listens before
it transmits. There will always be perfect doubles though.

>> If you don't have a digi at your disposal and UI-View is
>> the right tool and in the right place, then why not?
>
> If your area is remote from all other traffic, then of course,
> it is ok to generate these at home, but PLEASE limit them to 1
> hop.  The SPAM issue trumps all else.  I hate seeing a frequency
> object and then QSY to find *that it is 3 counties away that I
> cannot use*.

I'm anything but remote, but I just use one hop. To be honest, the
discussion has made me start thinking about changing my IGate over to
direct with no path, but I would probably want to upgrade from the
current quarter wave to a half wave or something along those lines
first.

>> In my opinion, a digi is not the right tool
>> to generate an object for an IRLP or EchoIRLP node.
>
> Maybe slightly better wording here would be..
>
> " the IRLP or Echolink node itself is the far better
> " place to generate these objects if you can afford
> " the extra radio and TNC....

In my opinion that would be a waste of an extra radio and TNC. In my
case, my IRLP node, IGate and digi are all at the same location. With
different antennas, coverage is different, but my IGate is exactly the
right thing to beacon my IRLP object to RF. As mentioned above, if I
upgrade the IGate antenna, I would very likely change the path to
direct instead of one hop. I would never degrade the IRLP object by
having something that doesn't know the status generate the object.

It all comes down to knowing what you are doing. A car or gun or fighter
jet in the wrong hands can be dangerous. An APRS client is exactly the
same way. You need to know how to use it. As I look around me, I can see
zillions of things that could be used improperly. Used correctly, they
do what they are supposed to do. I'm not saying that an APRS client is
the right tool to do everything with, but it isn't necessarily the wrong
tool just because it isn't a digi.

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




More information about the aprssig mailing list