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[aprssig] Any audio recordings of 144.390 MHz ?

Robert Bruninga bruninga at usna.edu
Sat Oct 24 22:15:04 UTC 2009


>> Yes!  Exactly,  Without RSSI, counting packet 
>> decodes is a completely meaningless statistic ...
> 
> Bob,  you are again running off the tangent...
> Instead of your feelings, I want raw received 
> audio as is. 

Hey, I aree with you completely.  That was the purpose of my
email, to encourage such analysis, because that is the only way
to properly analyze the channel as heard at one location.

> That raw audio is able to supply me RAW DATA 
> to MEASURE, not your hearsay.

My analysis is not hearsay. It is the logical observation on the
function of DWAIT=0 and fratricide in the network that some are
overlooking in their rush to endorse viscious digipeating.

>> Unfortunately, I do not think that the APRS-IS 
>> web pages can do any meaningful ALOHA calculations, 
>> because the calculation must be done on what a 
>> single receiver hears at a single location.
> 
> Like these ?
>   http://ham.zmailer.org/oh2mqk/aprs/oh2rdk-heard-direct.png
>   http://ham.zmailer.org/oh2mqk/aprs/oh2rdy-heard-direct.png

I tried them, bu the links did not work for me, but I assume
they are exactly what we need at each Igate.  I was saying that
a central site cannot make any analysis remotely based on other
Igate feeds, but each site can make its own analysis and make
the result available to the rest of the world, as apparenlty
your site is doing.  This works perfectly since each Igate knows
what it hears on RF (though it does not know what it doesn't
hear) which is the point we are both agreeing on.

> Note the massive asymmetry in both cases, 
> a "single number" really is not all that good.

The calculated ALOHA Range should not be interpreted as a
geographical circle, but a single unit of measure that is
independent of topology but represents the range from the
receive site that constitutes a full channel.  And since it is
calculated exactly the same way at each location, it reveals a
relative figure of merit.

>> IDEA!!!  Since the OUTPUT of an ALOHA calculation 
>> at any one site is a single NUMBER, we could ask 
>> ALL IGATES to make [frequent] ALOHA calculations 
>> and INCLUDE their ALOHA RANGE in their IGATE beacon.  
>> This way, we COULD capture this information
>> for local, regional and national analysis!
> 
> Isn't the idea in igate/digi that it does not need 
> to know where it really is? Nor look inside the 
> packets for deep analysis like packet originator's 
> coordinates?

Yes, for routine operations, but since we have Igates all over
the nation and world, this could be an additional function they
could perform.  I assume that most Igates have some form of
local client function and station lists, because they have to
have a LOCAL list to know what stations are their responsibility
to pass messages to.

Shucks, it would sure be nice if EVERY DIGIPEATER also had a
little smarts and could also report on its own RSSI.  That would
give some people a clue what the digipeater is hearing on its
input.  In its 10 minute beacon it could report:

"176RX, 109TX, 243 busy"

ON a ten minute basis (total 600 1 sec slots) this tells us that
176 packets were decoded at th is site, 109 were elegible for
further digipeating, and another 243 seconds the channel was
busy with other collisions and non decodable traffic.  Leaving
72 secnds the channel was clear.

This kind of info would be very helpful for analyzing the
network.  Maybe we can get some of the new digis to make  such a
report?

Bob, WB4APR





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