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ZL3AI > APRDIG 19.07.06 01:09l 186 Lines 6594 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 25 #16, 2/2
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Message: 6
Date: Sat, 15 Jul 2006 22:22:10 -0600
From: w0ep <w0ep_at_frii.com>
Subject: Re: [aprssig] Re: Unreasonable xmission delay
Which server are you getting your data from?
On Sat, 2006-07-15 at 21:04 -0700, BH wrote:
>I did a little analysis of APRS traffic this afternoon looking only at
>packets with $GPRMC sentences. Today's analysis looked at all $GPRMC
>sentences that I decoded vs the time that the packets were received.
>GPRMC includes the timestamp from the GPS, and my computer time is
>synced with an Internet time server. Here is the the data showing the
>callsign of the IGate, and the time delay for each individual packet
>rounded to the nearest second. There are some marked outliers which
>on further analysis showed was often do to corrupted packets, see the
>large numbers in the first station listed below. This IGate also
>shows marked delay in time, but then appears to improve with time. I
>understand that complete analysis would require looking at all the
>path data also. The idea here is to see where problems points may be
>located.
------------------------------
Message: 7
Date: Sat, 15 Jul 2006 22:39:05 -0700
From: BH <brent.hildebrand_at_gmail.com>
Subject: Re: [aprssig] Re: Unreasonable xmission delay
The Core Servers - Rotating.
w0ep wrote:
>Which server are you getting your data from?
------------------------------
Message: 8
Date: Sun, 16 Jul 2006 09:44:53 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: Re: [aprssig] Re: Unreasonable xmission delay
>>>brent.hildebrand_at_gmail.com 07/16/06 12:04 AM >>>
>I did a little analysis of APRS traffic this afternoon...
Looking at the ones with LONG delays, I notice they are also in the middle
of very high density areas.
N3XKU in the middle of New Jersey, The highest APRS density on the planet,
KD7NM in the middle of seattle, and N6EX-3 in the middle of Los Angeles.
Again, it is not inconceivable to me that in the vicinity of these IGates
is a digi somwehre on a high location that either hears too much or is
simply using carrier squelch and it takes forever for the DCD light to go
out so that the packet is finally transmitted. Maybe if we looked at the
path, we could learn something.
Bob
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Message: 9
Date: Sun, 16 Jul 2006 08:51:46 -0500
From: "john b. leonard, jr." <w9jbl_at_comcast.net>
Subject: RE: [aprssig] Re: Unreasonable xmission delay
One of our club members reported a big opening in 2m and 6m last nite.
That may explain why the system is hearing too much.
73s
w9jbl
dekalb, il
------------------------------
Message: 10
Date: Sun, 16 Jul 2006 08:56:04 -0500
From: "john b. leonard, jr." <w9jbl_at_comcast.net>
Subject: RE: [aprssig] Re: Unreasonable xmission delay
Also, when I listened to 144.390 yesterday here at home, it was non-stop
packet-racket. It was impossible for my system to get thru the 1st hop on
the digi here (WA9CJN-15).
w9jbl
------------------------------
Message: 11
Date: Sun, 16 Jul 2006 12:09:09 -0400
From: "Robert Bruninga" <bruninga_at_usna.edu>
Subject: RE: [aprssig] Re: Unreasonable xmission delay
>>>w9jbl_at_comcast.net 07/16/06 9:56 AM >>>
>Also, when I listened to 144.390 yesterday here at
>home, it was non-stop packet-racket. It was impossible
>for my system to get thru the 1st hop on the
>digi here (WA9CJN-15).
>>
>>>One of our club members reported a big opening in 2m and 6m last nite.
Good point. These band openings could really do that to our DCD lights.
Of course if that is normal for any given area, then it might be a good
idea to check all the surrounding digis and see if they support the New-N
protocol.
I see that WA9CJN is fully New-N compliant, so this comment is not to you,
but a general kibitz...
Getting most digis to set parameters to the New-N paradigm droped our
channel from 100% QRM down to periods as long as 10 seconds now when no
packets are heard... But we all still see each other, just more reliably
now.
Bob
------------------------------
Message: 12
Date: Sun, 16 Jul 2006 09:11:15 -0700 (PDT)
From: Jeff Thomas - KD4EVB <kd4evb_at_yahoo.com>
Subject: [aprssig] Re: Unreasonable xmission delay = big white elephant in
the room
I'll preface this I have little doubt there is something funky going on
with APRS-IS at times, but from reading this thread I think there is
another angle to be examined.... local RF network loading.
Here we have a mobile beaconing an appropriate (I guess for the area)
WIDE1-1,WIDE2-1 path. Problem is (IMHO) the 30 second beacon rate. This
strikes me as excessive unless needed for a specific situation (event,
emergency ops, etc). Come on folks, even at 60MPH in 30 seconds you've
only gone 1/2 mile at best! A few mobiles beaconing at this rate on top of
an already loaded channel can have a serious impact on local rf network
reliability.
Let's take a look:
http://www.findu.com/cgi-bin/near.cgi?call=K4COE
Looks like the ALOHA circle down there is only 30 miles. Approaching 400
packets an hour (that APRS-IS is seeing at least). 6 Digi's in that 30
mile radius (wow).
I can only imagine what the DCD lights on those digi's look like. It's one
thing to examine the rf level from a home station, but it's a whole
different view to look at things at the actual Digi site.
I remember a few years ago during the (WIDE,WIDE versus WIDEn wars) when
the local RF network here in the Ohio Valley was in shambles due to poor
configs, poor paths, and excessive beacon rates. I could go to the digi
site and wonder if the darn DCD light was stuck on. Even have a video
somewhere of it, it was a real eye opener. Folks if the DCD light is on,
nothing's getting digipeated during that time!
Things in the Ohio Valley are much better today, not perfect (still lots of
digi's using old standards to my south), but cleaning up the RF side of
things has made local communications much more reliable. At one time the
locals switched to 440 as 144.390 was a disaster is terms of loading and
reliability.
In short, nothing against K4COE persnoally, but if this stations setup is
typical for that area, I can only imagine how bad the RF level of things
are.
Again, there's definitely something goofy going on with ARPS-IS at times,
but let's not forget the other side of the equation...the local RF
networks.
Just a little food for thought.
73
Jeff
KD4EVB
------------------------------
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