[OZAPRS] Are 4 x iGates in Sydney too many?

Ray Wells vk2tv at exemail.com.au
Sun May 25 17:55:33 EST 2014

Guys and Gals,

Take a look at recommended paths and you'll see why multiple digis are 
retransmitting a station.

A mobile with WIDE1-1 WIDE2-1 will have two hops. Most, if not all, 
digis respond to WIDE1-1, so most digis will retransmit a WIDE1-1 packet 
for another hop (to any other digis that hears it) and that (those) 
digis will use the WIDE2-1 part of the path. A path of WIDE1-1 WIDE2-2 
will have three hops, extending the spread to another ring of digis and 
potentially more igates.

The reason for the closest igate not always being the one that appears 
on aprs.fi (et al) is that the nearest igate might be clobbered by 
another station that is stronger than the local digi - think FM capture 
effect - OR the received packet might be mangled in some way through 
collisions, and "lost", whilst a distant igate will receive a valid 
signal via its local digi and deal with it appropriately.

APRS is a bit (a lot!) of a free-for-all for channel access compared 
with connected mode packet where stations hold back transmitting, as 
defined by the channel access parameters of DWAIT, Slottime and 

A situation I see reasonably often is, I can be gating a station that's 
using vk2rcn-1 just fine, sending numerous packets to aprs-is and then, 
out of the blue a packet will go via a couple more digis to be gated by 
a station in Tamworth. I'm in Kempsey. Obviously my rx has been 
clobbered by vk2rdo-3, vk2rmy-1 or vk2jub-3 and I lost the packet.

Ray vk2tv

On 25/05/14 17:12, vk2ycj at bravo.net.au wrote:
> Gary,
> Interesting yes.   I can see a mobile station in Newcastle going to
> VK2RTZ-1 then to VK2RTG-5 rather than via our local iGate VK2ZEN-5
> VK2ZEN-5 looks like it's okay and working.
> Another mobile up the valley is going via VK2RTZ-1 and then to iGate VK2ZEN-5
> Maybe it's a difficult job to get to site and set the routing table on the
> VK2RTZ-5 digipeater if changes are needed.
> Can the routing tables be set remotely via the 145.175 access frequency OR
> can it only be done with a PC and cable onsite ?
> Jamie VK2YCJ
>> Maybe the "path police" should be looking at some of the digi's around
>> the place.
>> I wonder why I see traffic from sugarloaf on highrange being digi'd ? I
>> would have thought there are closer igates that the path should be set
>> (& honoured) that highrange wouldn't digi this stuff ? Maybe its
>> highrange at fault ?
>> On 25/05/14 15:20, vk2ycj at bravo.net.au wrote:
>>> G'day,
>>> I am thinking about using a hand-held 2m rig like a UV-5R as a low power
>>> "fill in" digipeater for a small country town ?
>>> I drive to Dungog from Newcastle (80Km by road north of Newcastle) 4-5
>>> days per week and the APRS coverage is poor or non-existent.
>>> I was considering two options:
>>> 1. Putting a UV-5R hand-held radio on a hill near Dungog as a "fill in"
>>> digipeater running 1-2 watts and solar powered.  The hill is line of
>>> sight
>>> to the main digipeater on the Sugarloaf Range in Newcastle.
>>> 2. Putting an Alinco DR-135T (with Argent Data card T2-135) running 20
>>> watts and not solar powered.  The boys at Goulburn NSW have installed
>>> two
>>> of these recently with good results.
>>> Can someone please comment on the suitability or stupidity of the above
>>> two options ?
>>> Thanks,  Jamie VK2YCJ
>>>> I have been looking at the load on one server in the rotation, which is
>>>> about to move hosting into one of my racks... which is why previously I
>>>> said there was no issue.
>>>> I do see some issues about the place, with a few WIDE3* and a few
>>>> NOGATE. I would have thought a NOGATE should also include NO-DIGI, but
>>>> its seems maybe I have the wrong assumption.
>>>> Maybe we do need someone to have a look at some of the paths being used
>>>> and clean them up.
>>>> I would have thought its best to try and keep RF clear so more can be
>>>> handle without drama.
>>>> Gary
>>>> vk2zbb/vk2lv
>>>> On 25/05/14 11:50, Scott Evans wrote:
>>>>>    From a T2 perspective there's no issue! If you're using
>>>>> aunz.aprs2.net
>>>>> rotate the load balancing is automatically taken care of, however if
>>>>> you
>>>>> have set up a static server and if everyone else had done similar then
>>>>> maybe a problem would exist!
>>>>> On May 25, 2014 11:32:59 AM GMT+10:00, Liz VK2XSE <edodd at billiau.net>
>>>>> wrote:
>>>>>       QTR Thu, 22 May 2014 21:47:13 +1000 Ian Mills QTC
>>>>>           I've noticed we now have at least 4 x iGates in Sydney, I
>>>>> would
>>>>>           have
>>>>>           thought that's too many and may be adding extra loads on the
>>>>>           sever as
>>>>>           they all gate the same traffic?
>>>>>           Ian vk2him
>>>>>       The guys in the US, who have more experience in handling large
>>>>> traffic
>>>>>       volumes, seem to whinge far more about excessive digipeating than
>>>>>       excessive iGating.
>>>>>       I did notice on my last trip to Wollongong that my packets were
>>>>> being
>>>>>       spread far and wide, and often gated from Newcastle after being
>>>>> picked
>>>>>       up by VK2AMW-1. (WIDE2-2)
>>>>>       The questions can best be answered by experimentation.
>>>>>       There is apparently a need for better RF coverage in Sydney. How
>>>>> much
>>>>>       redundancy is required in the iGating system could be explored
>>>>>          by
>>>>>       deliberately turning off internet connectivity at one or more of
>>>>> the
>>>>>       Sydney iGates.
>>>>>       Sydney users would need to know when these changes were made, and
>>>>> then
>>>>>       comment on negative and positive aspects of the changes.
>>>>>       We would also need to know how many hops people are using in
>>>>> their
>>>>>       transmissions.
>>>>>       And is there any information from the APRS-IS server operators
>>>>> about
>>>>>       network load?
>>>>>       -+-+-+-+-+-+-+-+-+-+-+
>>>>>       Liz
>>>>>       VK2XSE
>>>>>       who hopes not to be using APRS in Sinny, 15 years living there
>>>>> was
>>>>>       enough.
>>>>>       ------------------------------------------------------------------------
>>>>>       OZAPRS mailing list
>>>>>       OZAPRS at aprs.net.au
>>>>>       http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>>>> --
>>>>> Sent from Kaiten Mail. Please excuse my brevity.
>>>>> _______________________________________________
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>>>>> OZAPRS at aprs.net.au
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