[aprssig] most packets are transmitted blind (was: Please,

[Robert Bruninga]

>>> there are 350 other user packets flying 
>>> around and most of them are blind 
>>> transmitters that could care less what 
>>> they collide with.
> 
> Even the "blind" trackers you belittle so 
> much have a squelch detect circuit.

Ah, this pushes a rant-button:

That is a very minor point, every mobile, every weather station
and almost every hoome station usually cannot hear more than 2%
or so of the activity on the channel *even-if* they have
sensitive receivers.  They *cannot* hear the other 98% of
stations direct, and it is those other 98% that they have the
potential to collide with when they transmit.  And there is
*nothing* they can do about it.  It is the nature of using a
simplex ALOHA network even with CSMA.

So I was not at all talking about one-way trackers, I was
talking about almost ALL APRS stations are practically "blind"
to all the other users and cannot avoid collisions at the input
to the digis..

> There's whole new product lines of high power...
> trackers that have no receivers...

True, but it just does not really make that much difference.
Even if they had receivers, they could still can do nothing
about colliding with any of the other 98% of all local users
that they cannot hear directly.  The ONLY thing they lose by not
having a receiver is colliding with the digi, and the only
person that hurts is themselves.

> Amateur stations that automatically transmit 
> without first listening to check if the 
> frequency is clear?  Is this even compliant 
> with the letter or intent of rules, or even good 
> operating practice?

Think cleary about what one hears when one listens...  Usually
only 98% of what he hears is the digi, and maybe a rare nearby
mobile is the other 2%.  All the rest of the time, hearing
silence hardly tells one anything at all about a collision with
another user.  It only tells you whether you have a chance for
the digi to hear you.  But the other 350 users in the area are
sharing that same chance and since they cannot hear each other
direct, there is not a thing they can do about avoiding it. (GPS
slotted assignments really does help in events, where you can
organize things)...

> Every Ham should be against this sort of thing.

But first they need to think clearly about what they are
against.  Even if we had perfect operators that always listen
first, the improvement to the network (for all the others) would
only be a few percent at the most.  Hardly worth all the angst
that this topic brings up every time it comes up.

By the way, I my rants against trackers is not because they have
no receivers, its because they do not give us any information on
how to be in immediate *communication* with the Ham operator
driving the vehicle, and second, they are a clear indication
that that operator is driving blind and has no idea what is
going on in the APRS network around him.  And you cannot send
him information, nor extract anything from him for the purpose
of the local situation.  He may as well be a pizza delivery man
as far as providing any benefit to the surrounding community.
Even if he had a load of pizzas. You couldn't send him a message
to bring one by here...

I am not opposed to every ham buying or building as many
trackers as he can afford, so that he can bring them to events
and put them on things that need to be tracked.  But if a HAM is
in the car, then he needs to be receiveing APRS info and
messages too.

Hope that helps
Thanks

Bob, WB4aPR