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[aprssig] Local Event using RELAY?

AE5PL Lists HamLists at ametx.com
Sat Apr 2 14:45:34 UTC 2005


> -----Original Message-----
> From: Henk de Groot
> Posted At: Saturday, April 02, 2005 8:29 AM
> Subject: Re: [aprssig] Local Event using RELAY?
> 
> Sorry but we are talking about the channel access 
> characteristics only, not the full ALOHA network. ALOHA in 

But the numbers you espoused from the ALOHA project are not about
channel access only but about their findings with retries.

> Now for your APRS area being mostly CDMA. I have to agree for 
> home-stations, digipeaters and others with good antenna's and 
> terrain that allows you to hear eachother. But if I take my 
> TH-D7 outside with its rubber-duck, the TH-D7 can only hear 
> the digi - at least frequently...

But you obviously missed that most of the packets that the TH-D7 is
competing with are from that digipeater and therefore it too is
operating CSMA.

> While reading your mail I also had another strange feeling. 
> If every station can already hear all its neigbours, why do 
> you have a digipeater? 

I said hear, not decode.  Big difference.

> Okay, I'll leave it with that. I think the raised points are 
> clear and I even think we don't disagree much. Avoid however 
> to take things for granted because you once learned that 
> doing something is a bad thing. Keep an open mind and dare to 
> question these kind of general assumptions.

I have not.  I did question your general assumptions and showed their
fallacies.  You might think about following your own advice and not
discard a reasoned objection just because you think its ok to transmit
in-the-blind on the shared APRS channel.

> By the way, did you know DAMA also works without carrier 
> detection? In DAMA the master (the node) does the listening 

Yes, but it uses a different type of collision avoidance and immediately
begins to fail when non-DAMA activity occurs on the same channel.

> Another example of running without carrier detection is Full 
> Duplex connection on a point to point link. Its just assumed 
> that you are the only transmitting station on one of the two 
> QRG's of the FD link. All our packet interlinks on 23 cm work 
> that way.

Again, completely irrelevant to the topic.

73,

Pete Loveall AE5PL
mailto:pete at ae5pl.net 




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