[OZAPRS] Digipeaters and iGATE's

Sun Oct 19 09:16:48 EST 2014

Peter,

APRS is different things to different folk.

Some see its original purpose, position reporting, as the priority.

Others followed Bob's thinking that here was a packet passing network
that could be utilised for all manner of purposes.

The fundamental tension between these two is that position reporting is
degraded as channel utilisation increases, and use for other purposes
degrades position reporting.

I have studied the causes of packet loss (meaning packets that were
transmitted that did not find their way accurately to APRS-IS) and the
causes are many fold, and most of the root causes result in high channel
utilisation which is the indirect cause of most packet loss.

In the beginning, there were digis as a means of sharing position data
over a wider geography.

Then came iGates which provide a superior method of sharing position data.

In this area (I live just SW of Sydney), all prominent digis are
captured by two or more iGates, so you might question the need to
shuffle packets along through three digis... but it is done and it is a
major cause of congestion.

If you have a reliable iGate on a prominent site, it can be argued that
it should not digipeat at all because it only raises congestion without
improving packet flow to APRS-IS.

Indeed, repeating the packet only risks sub standard iGates submitting
corrupted packets (there are something like 10 such digis that get hold
of my packets and corrupt them).

I have been in conversation with the author of Microsat about smarter
filtering capabilities for digis, and he understands the case for
filters that drop packets on hop count, or that have passed through
digis in a drop list... but it is not yet implemented. For the most
part, the digi network cannot do intelligent routing... Bob's "New N
Paradigm" of a decade ago was a mid life kicker for APRS that is not up
to the current need.

If you have access to a prominent site and have affordable Internet
access, I suggest you install the node as iGate ONLY, and that you
configure it to use pre/de emphasis in tx/rx as was originally intended.

Be very cautious about iGating ANY IS to RF. The channel utilsation
during busy hour halved here when a ham who was iGating his buddies to
RF three digi hops away flooded the channel with unwanted traffic.

Not everyone will agree with this approach I am sure... so ask around.

Owen

On 19/10/2014 8:50, VK3AJ wrote:
>
>  
>
> Greetings to all on this list,
>
>  
>
> I manage a number of radio sites here in Victoria for Scouts Victoria
> as well as myself in significant locations.
>
> Since getting a nice new TM-D710GA to play with, I have been getting
> more interested in APRS and how it works.
>
> I noticed some significant holes in the APRS coverage in the areas my
> voice repeaters cover, so have started the process of establishing
> APRS on one of the sites (VK3RSA) to fill these holes and learn more
> about how the network works.
>
> I’ve tried contacting our Victorian APRS coordinator to no avail, so
> are seeking advice from members of this list on the right way to set
> it up, how best to configure it for best performance and not have an
> adverse effect on the APRS network.
>
>  
>
> The site has excellent free high speed internet access, so I am
> interested in setting it up as an iGATE as well.
>
>  
>
> So to specifics.
>
>  
>
> The hardware is a Microsat WIN3in1 mini connected to a 25W Motorola
> MCS2000 mobile into a Folded Dipole antenna on a water tower 48m AGL.
>
>  
>
> The site is a high mountain that has 360deg visual coverage for 100+
> Km in 85% of horizon. Nearest obstructive mountain is the Dandenong
> ranges 15Km away.
>
> Current tests from the site shows significant coverage improvements
> across the area.
>
> Some of the information I have read on the internet (so it must be
> true J) suggests that APRS sites on high mountains aren’t necessarily
> a good option. Is this correct?
>
> The site shows a path from my mobile (VK3AJ-9) as SW55Q7 via VK3RSA-1,
> WIDE*,WIDE2-1,qAR,VK3GY-1. I’m note 100 percent sure what all this
> means, but have noticed that other sites show WIDE1-1 where mine shows
> WIDE*. What effect does this have?
>
> Can anyone advise the correct settings for a WIN3in1 mini in such an
> environment?
>
>  
>
> How do I go about setting it up as an iGATE? Is this an appropriate
> option?
>
>  
>
> I have three other sites that I could add APRS to depending on
> appropriateness. 1 is in a rural area not currently covered by APRS
> (SW corner of Victoria) and the other 2 are outer eastern Victoria
> sites. How do I get / Who is best to advise me on suitability of these
> sites for adding to the network?
>
>  
>
> I’m a hands on learner, so please, no highly technical answers.
>
>  
>
> Thanks in advance for the collective wisdom.
>
>  
>
> Regards,//
>
>  
>
> */Peter Chaplin/*
>
> */peter at chaplin.net.au/* <mailto:peter at chaplin.net.au>
>
> */VK3AJ/*
>
> */Scout Radio & Electronics Service Unit/*
>
> */Repeater Coordinator/*
>
> */0418 328 882/*
>
> / /
>
> /No trees were harmed in the posting of this message...however an
> extraordinarily large number of electrons were horribly inconvenienced./
>
>  
>
>
>
> _______________________________________________
> OZAPRS mailing list
> OZAPRS at aprs.net.au
> http://lists.aprs.net.au/mailman/listinfo/ozaprs
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