[aprssig] Local Event using RELAY?

AE5PL Lists HamLists at ametx.com
Thu Mar 31 09:08:06 CST 2005

Let me reiterate as you apparently didn't understand my posts:
#1 - ALOHA is not transmitting in-the-blind.  It is a much more complex
protocol which is significantly different from APRS.  The term has been
misused extensively here to justify people using the statistics gathered
in that project which are not related, in any way, to VHF APRS
#2 - Yes I live in an area with a dense concentration of stations.
However, my home QTH is NOT in a densely populated area.  To point, it
doesn't matter.  If 70 or 80% of the packets heard in your area are
digipeater packets, then you are running CSMA regardless of your HAAT if
you see that digipeater.  Simple math: if you are the only station
within the hearing range of the digipeater and you are beaconing a path
that is digipeated, over 50% of the packets in your area are digipeater
packets (the digipeater beacons too).  As you add stations, regardless
of whether you hear them directly or not, the percentage of digipeated
packets continues to increase.  True, it is doubtful that you will
interfere with your own packets being digipeated, but the moment you add
another station, those odds increase dramatically.
#3 - While I feel that transmitting in-the-blind is poor operating
practice and in some instances illegal in the USA, the promotion of such
operation as justified by the errant use of ALOHA numbers or incorrect
statements such as yours is just plain wrong.

I don't know how to make it clearer so I am done trying.  Good luck and
please keep your transmit-in-the-blind operations out of my coverage


Pete Loveall AE5PL
mailto:pete at ae5pl.net 


	From: John Kraus
	Posted At: Thursday, March 31, 2005 8:27 AM
	Subject: RE: [aprssig] Local Event using RELAY?
	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
	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.
	The single easiest way to differentiate is by looking at RF
range and that is largely a function of antenna height and topology.

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