[aprssig] Local Event using RELAY?

Robert Bruninga bruninga at usna.edu
Tue Mar 29 14:15:13 CST 2005

>>> HamLists at ametx.com 3/29/05 2:03:17 PM >>>
> AX.25 UI packets are transmitted using CSMA with a
>varying probability... that one station will try to transmit 
>at the same time another station is without being able to 
>hear (at all) the other station.

Yes, but when you use a digipeater, then typically you 
can only hear (and avoid a collision with) about 3 % of
the stations on the air (I see 300 stations, but can only
hear 4 or 5 direct).

>For Bob and you to promote transmitting in the blind is
>counterproductive to establishing a stable APRS 
>environment of benefit to the most users. 

That is a malicious stretch of the truth.  We never advocate
transmitting in the blind without consideration of the situation.
And all that we said was that in the case of a flea power
tracker it may be more effective to digipeatr through your
mobile to get out.  And in the case presented, the venue
was out in an area where the mobile could probably
not hear any other stations, and thus could not avoid
collisions and thus there is little difference between whether
it listened first or not.

That is simply a statement of facts and an education of
the user to how APRS typically might work in that RF
domain.  No where is is a "promotion of transmitting
in the blind.".

An educated user is better than a user just 
"transmitting in the blind" without knowledge of
the impact of his transmissions...


> -----Original Message-----
> From: Henk de Groot
> Posted At: Tuesday, March 29, 2005 12:34 PM
> Subject: Re: [aprssig] Local Event using RELAY?
> Hello Pete,
> Now why does this come up now? We had lengthy discussions on 
> the SIG about ALHOA and the maximum 18% channel load. 
> Transmitting blind *is* exactly what ALOHA is all about and 
> nobody argued agaist it.

And I certainly did but you obviously weren't listening.

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