[OZAPRS] WIDE1-1 (was: European v USnewparadigmand pathlimiting+confusion....)

[Chris Hill]

Hi Gavin,

Possibly...


However, if we map the 50% reliability coverage of your home station, my
home station, VK6RVP-1, VK6KSB-1, VK6KRB-2 and VK6RLK-1, we end up with a
very high likelihood that almost all packets will be heard and digipeated
by
two or more stations at the same time, with large areas of the composite
coverage having less than say 12dB of difference in signal strength coming
from each digi.

In practice, this will mean that "normal" APRS stations will fail to
decode
the digipeated packets, due to the collisions.

Most FM demodulators work "OK" with a co-channel ratio of 12dB or greater,
so I think we should aim to have "simultaneous digipeaters" sited such
that
they have minimal overlapping coverage with less than 12dB of signal
difference.

This isn't easy to do, but for example I believe that the poor coverage in
the northern suburbs of Perth needs to be addressed with either an
omnidirectional digi up around Edgewater, Wanneroo or even Two Rocks way,
or
a digi on a tall building in Perth, with a Yagi pointing north (an omni in
Perth would be a bad idea).


Of course, with the low channel loading in VK6, we could just use "DWAIT
ON"
to help address these issues...


... or, having a look at the 90% reliability coverage for Perth, I wonder
if
it is wise to have home stations acting as "WIDE" digipeaters anyway?
There
is very little need for such "infill coverage", except for the gap north
of
Balcatta.  (The composite 90% coverage is shown at:

http://vhf.wirelessplanet.com.au/aprs/VK6KRB-2_VK6RBC-1_VK6KSB-1_VK6RLK-1_
1u
v_9090_coverage_with_nodes.png



73



Chris
vk6kch



-----Original Message-----
From: ozaprs-bounces at aprs.net.au [mailto:ozaprs-bounces at aprs.net.au] On
Behalf Of Gavin Rogers
Sent: Tuesday, 7 November 2006 2:51 PM
To: VK / ZL APRS Users
Subject: Re: [OZAPRS] WIDE1-1 (was: European v USnewparadigmand
pathlimiting
+confusion....)

Chris Hill wrote:
> Hi Andrew,
> 
> Is there an advantage to having a path of "WIDE1-1, WIDE2-2", instead of
> "WIDE3-3"?
> 
> I would have thought that the slightly shorter packet (approx 10%
shorter)
> would be preferable, as it has a slightly better chance of being decoded
> error free at the first digipeater (and hence accessing the network).


I'm learning here too, but doesn't WIDE1-1 activate fill-in digis (aka 
RELAY stations?). A fluttery mobile station might not get a decodable 
packet into a WIDE2/WIDE3 digi but has a better chance being relayed by 
another user's home RF station first.



73
Gavin
-- 

       Gavin Rogers                     |  Amateur radio station VK6HGR
     http://www.livingwaters.com/good   |     http://vk6hgr.ampr.org/
    ICQ: 17230395          Skype/MSN/Email: grogers at vk6hgr.echidna.id.au
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