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<font size=3>At 07:19 AM 3/31/2005, you wrote:<br>
<blockquote type=cite class=cite cite="">
________________________________<br><br>
<x-tab> </x-tab>From: John
Kraus<br>
<x-tab> </x-tab>Posted At:
Wednesday, March 30, 2005 10:21 PM<br>
<x-tab> </x-tab>Subject:
RE: [aprssig] Local Event using RELAY?<br>
<x-tab> </x-tab><br>
<x-tab> </x-tab>At 09:00
PM 3/30/2005, you wrote:<br>
<x-tab> </x-tab><br><br>
<x-tab> </x-tab><x-tab>
</x-tab>Ah ha!!!
The light came on for me! Henk and I are<br>
talking apples to Pete's<br>
<x-tab> </x-tab><x-tab>
</x-tab>
oranges... Apples and Oranges...<br><br>
<br>
<x-tab> </x-tab>This
discussion is silly. <br>
<x-tab> </x-tab><br>
<x-tab> </x-tab>The key is
to understand that the primary factor that influences<br>
whether a station is CSMA or ALOHA is, at its most basic, simply a<br>
matter of antenna height or more succinctly HAAT. <br>
<x-tab> </x-tab><br>
<x-tab> </x-tab>If a
station is running near a unity gain antenna at less than<br>
10 ft above ground it is almost always functionally ALOHA. The<br>
exception being when it is on a high site or is located in a station<br>
dense area.<br>
<x-tab> </x-tab><br>
<x-tab> </x-tab>Conversely
if it is located at 300ft HAAT or on a mountain it is<br>
mostly CSMA. <br><br>
I did not receive Wes's email via TAPR so I will respond to his email
as<br>
a SIG post in my next post. As to your statements above, they
are<br>
incorrect. Reread my original post. That station with the low
HAAT is<br>
most definitely running CSMA to over 90% of the packets being
generated.<br>
Actually, it is running closer to CSMA for 99% of the packets on the<br>
frequency when you take the time to do the math and take into<br>
consideration what a station can _hear_ versus what a station can<br>
_decode_. This is a very important distinction which your
statements do<br>
not take into account.<br><br>
73,<br><br>
Pete Loveall AE5PL<br>
<a href="mailto:pete@ae5pl.net" eudora="autourl">mailto:pete@ae5pl.net</a>
<br><br>
_</font></blockquote><br>
You are located in a "station dense area". The station in
my example is not. Neither are stations located throughout much of the
geographic area of the US. I stated in my example that the low
station could only hear the digi. It is ALOHA to everyone else on
the frequency.<br><br>
The key concept that continues to be missed is that APRS is a mixed CSMA
/ ALOHA network. Stations that are CSMA should not transmit
blind. Stations that are almost always ALOHA can be granted the
ability to transmit blind under special circumstances.<br><br>
The single easiest way to differentiate is by looking at RF range and
that is largely a function of antenna height and topology.<br><br>
============here is my text again.===============<br><br>
<font size=3>Ask this question:<br><br>
If the transmitting station can not hear <b>ANY STATION</b> but the digi
who will be harmed by its transmission in the blind? If the digi and the
ALOHA collide who loses? <br><br>
The answer in both cases is nobody.<br><br>
Nobody is harmed by the blind transmission.<br><br>
The ALOHA station must accept the loss of this packet as part of
"its" network design it is expected and unavoidable therefore
not harmful.<br>
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