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Re: Brief msgs via 9600 Pacsats?



I can only speak from personal experience, but my impression
from watching my station operate is that most of the 9600 
bps pacsat operators are running full automatic for at 
least half the day (and most are 24x7.)  I tried 
"hand operating" on selected passes, and it simply
wasn't feasible.

  My station at my last qth was badly obstructed,
but still usable if I followed all the passes and caught
what data I could (usually 300-500kb./pass)  What I found was
that if I shut the station down for a day,  my station
spent all its time for the next several passes fighting 
its way into the queue for directory fills that nobody else 
needed.   Not only did this waste my time, but the fill
requests interferred with other folks's uploads etc. 
(And I averaged an 'OK' for about every 4-5 fill requests
I sent, when the satellite was over canada, and 1 in 10
when the satellite was in view of the US east coast.)
The situation was far worse before I fixed my desense
problem, since I think I was missing a lot of the 
satellite responses.  (This would be true for a slow
half duplex operation as well.)

  Conversely, if I left it running, I got the benefit of
needing the same fills that all the other users needed,
usually the most recent messages.)  There were times
that it took more than 24 hours to get fully caught
up on the directory, and this was after I had instructed
wisp to fill the directory before doing any downloads. 
(The better stations in better locations probably have
an easier time of this.)

  I seriously doubt that a casual user such as a hiker
could turn on  a station, and get fully caught up 
in one pass, to the point where he could be confident
that there were (or were not) any messages addressed
to him. (More likely, he could upload small outbound 
communications, but not with the degree of reliability
required for so called "critical" communications.

  The reason I stopped operating on the pacsats was
related to the amount of "work" my station needed 
to do in order to stay current, and the associated
wear and tear on the az/el rotators.   (A "no moving parts"
antenna with enough gain to hear the birds from
horizon to horizon would have me back on in seconds...)
 
 IMHO,  a 'list mine' function (possibly  implemented as a 
special case of a broadcast fill request) would be 
a HUGE  advantage and would probably decrease 
downlink congestion quite a bit,  since there
are many "marginal stations"  (such as mine) who would
be willing to dispense with the full directory if we could
just find/download messages addressed to us.  This would
also go a long way towards allowing folks such as Bob
who want to be able to operate in more of a "hit and run"
fashion (no insult intended) to do so with a 
laptop/yagi/HT from the field.  (And IMHO, field operations
are where pacsats excel, especially now that large
amounts of people have decent home internet service.)

-------------

Bob Bruninga wrote:
> 
> On Thu, 22 Oct 1998, al lawler wrote:
> 
> >   1)  Operating the pacsats without some form of doppler control is
> >       virtually pointless for anything other than quick demonstrations.
> 
> Or essential critical communications if you have no other means to
> communicate.  I am not proposing this for routine operations.  But trying
> to see if the radio is useful for rare, but necessary commmunications in
> remote areas with no other alternatives.
> 
> With the IF bandwidth of the Kenwood HT, It works perfectly with just
> three settings, +5, 0 and -5.  Relatively easy to do in an 8 minutes.
> 
> >   2)  Running half duplex, it sounds like you could possibly
> >       miss lots of 'ack' messages, thus causing a lot of
> >       needless resends.  This doesn't really seem all that
> >       friendly to the other users, particularly given
> >       how congested the 9600 bps birds can be.
> 
> No intention to do so.  The question was asked, and the answers confirm it
> is not possible.  Thanks.  We're learning...
> 
> >   3)  The pacsats have no "list mine" function.  Without a complete
> >       directory, you wouldn't even know if a message for you existed.
> 
> This is a good point.  THanks.   Any work around ideas?
> 
> I do assume that a hiker or boater or other station needing to access
> the Pacsat would listen the entire pass.  But then if he doesnt listen
> every pass, then he is not building up the directory.  Hummh.  Lets say he
> only checked in once a day.  About how many directory entries are there on
> average per day?
> 
> I do see that his directory fill requests does add bandwidth if we assume
> that all the other operators are running automatic and get the directory
> piecemeal.  His Dir request would be larger than the others...
> 
> That would be a nice statistic to know  in general anyway.  What are the
> operational habits of most stations?  Automatic/every pass/every day?
> 
> I noticed that only 5% or less of the PACSAT messages were to/from USA
> callsigns.  Is this true in general or was this unusual for the few passes
> I have worked so far?
> 
> Still learning.  Thanks
> 
> de WB4APR, Bob
> 
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