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Re: Brief msgs via 9600 Pacsats?



I've been sort of half following this thread, but it seems
that a few points need to be clarified.

  1)  Operating the pacsats without some form of doppler
      control is virtually pointless for anything other
      than quick demonstrations.

  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.  (And 
      (accidently or otherwise) sending duplicate requests 
      while in the queue is counter-productive,
      in that you forfeit your current spot in the queue
      and go back to the end in most cases.

  3)  The pacsats have no "list mine" function.  Without
      a complete directory, you wouldn't even know if
      a message for you existed.  (Or to put it another
      way,  "hit and run" type of operations don't work
      well on the pacsats.   The most efficient way to
      operate is to be able to listen for entire passes. 
      It's feasible to 'pop in and upload' a quick message,
      but not feasible to recieve messages via this 
      route.)


IMHO, "APRS like" operations really aren't feasible on 
these birds, particularly with the configuration you're 
proposing.  The mechanics of keeping a yagi hand pointed
at the sky, while tuning an HT with the other hand
(and typing on the computer with a third) really isn't
feasible for any type of "real" use.

 A small full duplex radio, and some form of high gain 
omnidirectional antenna (or electronically switched 
array) which could passively listen for most of a pass 
would probably prove to be  far more useful, and 
wouldn't be limited to very short 'aprs like' 
transmissions - you could send and recieve 
anything you wanted...

  -al



Bob Bruninga wrote:
> 
> On Wed, 21 Oct 1998, Paul Williamson answered questions about finding ways
> to use the Kenwood 9600 baud TNC/HT for communicating via satellite:
> 
> > You should be able to receive arbitrary messages with little problem.
> > The transmission you make to request transmission of a file is a UI
> > frame.  The file you request generally won't be transmitted immediately,
> > so your receiver will have plenty of time to change bands while your
> > request is in the queue.  An exception is made for extremely short
> > requests -- they're jumped to the front of the queue.  So, you might
> > have to rely on downlink congestion for delay when you're asking for
> > an extremely short file or for a small "hole" to be filled.
> 
> Thanks Paul.  So it does seem like a very slow T/R transceiver can still
> "request" a download without too much difficulty.  That seems to solve the
> problem then.  A wilderness user can at least then "check for mail from
> Home or emergency messages".  Thats good news...
> 
> de WB4APR, Bob
> 
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