[aprssig] Audio Feedback for APRS Packets and Messages on the TH-D72
vk2tv at exemail.com.au
Sat Jul 27 02:32:46 CDT 2013
On 27/07/13 01:16, Robert Bruninga wrote:
> On Thu, Jul 25, 2013 at 7:34 PM, Tony VE6MVP <tony at ve6mvp.com> wrote:
>> At 01:48 PM 2013-07-24, Robert Bruninga wrote:
>> The most important thing to realize is that if you can hit TWO
>> digipeaters, then the chance is very high that you will NOT get a
>> “MY PACKET” display since both of those digis will BOTH
>> digipeate your packet at the same time
>> and you will always get a collision.
>> The folks here in central Alberta have been reconfiguring the digi's
>> to have different delays when repeating packets for exactly that
> But it is not a "problem" It is how APRS was designd for maximum
> throughput. APRS is designed to key up all digipeaters that heard a
> packte at the *same* time. This assures that a 2 hop packet will go 2
> hops in all directions in only *two* time slots. That is why DWAIT is
> always set to zero.
> If you add delays you will cut the performance of the APRS network by
> a factor of FOUR or more. It would be shooting yourseves in the foot!
> Each digi can hear usually 4 or more other digis (they dont have to
> deconde them, just hear them, and then each of those can hear four
> more. SO you can have one packet taking up to 16 time slots as each
> digi awaits its turn!
> Please do not do this. It is not a "problem", it is users needing to
> understand how the network works and recognizing that just because
> they don't "see" every "my-packet" does not mean at all that the
> packet did not go out.
> Fratricide of all those dupes was fundamental to the design of the APRS system.
> Hope that helps.
> Bob, WB4APR
There is a fundamental difference between unconnected packet (ui - read
as aprs) and connected mode packet (bbs, nodes, etc) where timing for
collision avoidance (maximum channel utilisation) is so important. For
aprs, parameters such as DWAIT, Slottime and persistence are set to be
as aggressive as possible - quite a contrast to the "be nice" settings
some of us are used to.
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