Re: Message retry


kc8sfq
 

Hi Rob, Thanks, That makes it a bit clearer. Since we'll be real proud to
get 3 dumb trackers and two digis, circuit loading may not be as big a
problem as I had envisioned. Right now, we are probably on the flat spot
at the bottom of the learning curve. It's all up hill from here, right?.
73, Ron (KC8SFQ)
+++++++++++++++

Let me try this again.SlotTime and Persist are TNC parameters (not
APRSIS32 or any other computer app). They are used to space data "when the
frequency is clear".
If you have 15 TNCs all waiting to transmit and the frquency becomes
clear, ALL 15 will MOST LIKELY transmit at EXACTLY the same time (since
they all "see clear RF" at the same time).  To avoid this, the TNCs use
an algorithm with SlotTime and Persist to try and spread them out:
  Persist is a probability calculation
  SlotTime is a "very short delay" in milliseconds - actually value x10
milliseconds.  So a value of 15 is 150 ms delay.  
SlotTime itself CANNOT delay a packet by even seconds, let alone 10
minutes.

The Beaconing stradegy (Genius, Smart, or any other) is used by the
"computer" (or micorprocessor) to determine when to send data to the
TNC.  This results in time that are typically in "minutes".   When that
time is up, the data is passed to the TNC, but the TNC has to determine
when to TX over a clear frequency which will allow other stations to hear
the packet.  SlotTime and Persist determine that.


 Robert Giuliano KB8RCO

From: "kc8sfq@... [aprsisce]" <aprsisce@...>
To: aprsisce@...
Sent: Wednesday, May 11, 2016 5:23 PM
Subject: Re: [aprsisce] Re: Message retry

  Hi Rob,
If the Genius calls for a beacon, but the slot time doesn't come around
for (lets say) ten minutes, Which takes priority? Will the TNC wait for
the next ten minute window? or send the packet called for by Genius? The
COMMS director for the race we're prepping for seems stuck on 15 minute,
time only beacons. I'm trying to convince him that 15 min is a recipe for
failure of APRS as "REAL TIME tactical information". (it seems like I
heard that phrase somewhere <G>). The lead cyclists can easily cover 4-5
miles in that 15 min time.

Time slotting is a technique used by the TNC to help avoid data
collisions
on the air........ These are typically very short delays.
How short? How tightly do I dare slot 3 or 4 trackers? I have been
following a thread, elsewhere, about not using DWAIT on DIGIs

Q2: APRSIS32 has 3 places to enable internet stuff:
I have all those up and running, as well as RF with various radio/TNC
combinations and SSIDs as I test equipment. You can find me between Battle
Creek and Grand Rapids, just west a ways from you. SSIDs vary, but
usually: -0, home and probably attended, though I'm not staring at it; -9,
mobile; -11&12 are the DIGIs; -13 is a tracker, and my wife's tracker is
KC8UJA-9 I still have two trackers to build yet, but that is mostly
hardware. That's the easy part.

The part I am working on though is making one of the DIGI-APRSIS32 combo's
work as an IGATE. I have IS to RF and RF to IS both set to on, but the
VIEW LOGS/ IGATE ENABLED tab shows it to be DIS abled. It seems to me that
I read here some time ago that all I had to do was check IS to RF and RF
to IS, and APRSIS32 would be an IGATE. That computer also has my passcode
in the proper box to allow IS access.

73 and thanks, Ron (KC8SFQ)

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