[aprssig] Any audio recordings of 144.390 MHz ?

Matti Aarnio oh2mqk at sral.fi
Sat Oct 24 13:26:57 EDT 2009

On Sat, Oct 24, 2009 at 12:29:25PM -0400, Robert Bruninga wrote:
> > More precise measurement would take radio 
> > RSSI signal, and account fraction of time 
> > when it is over some defined treshold.  
> > That would know not only of successfully 
> > decoded packets, but also of failures
> > due to two transmitters colliding at too 
> > even signal power levels.
> Yes!  Exactly,  Without RSSI, counting packet decodes is a
> completely meaningless statistic as far as channel loading is
> concerned.  Decodes only show success.  There is no way for
> decodes to show all the failures.  And without comparing the
> two, then there is no conclusions to be drawn as to network
> performance.

Bob,  you are again running off the tangent...

Instead of your feelings, I want raw received audio as is.
I can make educated guess of "got some carrier" while there is no
decodable packet.  Then I can make guestimates of how much there
really is fracticide going on.  Heck, I could teach my testbed
softmodem to periodically report REAL Erlang values!

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

Your hearsay may have some truth behind them, but I want real data.
I also want them from different places, I can do that well enough here
in Helsinki conurban area, I can get same from couple other places
in Finland,  but I really want to see how things are in places like
Austin, Houston, and LA ?

> 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.
> And since the APRS-IS throws away dupes, this makes remote
> monitoring impossible.

Like these ?

These igates do log all heard packets on a local file, and
I wrote a script to plot what I found there.

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

But at first I do need some _real_ audio from radios.
The "TNC test CD" mentioned here is useful start, but I need more.

> IDEA!!!  Since the OUTPUT of an ALOHA caclullation at any one
> site is a single NUMBER, we could ask ALL IGATES to make
> continuous ALOHA calculations and INCLUDE their ALOHA RANGE in
> their IGATE beacon.  This way, we COULD capture this information
> for local, regional and national analysis!!!
> Is anyone actively writing Igate code that wants to add this?

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?

Sure I disregard such notions, but YMMV and all that...

> Bob, WB4APR

73 de Matti, OH2MQK

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