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ZL3AI > APRDIG 26.10.06 07:06l 277 Lines 10925 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 28 #9, 3/4
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From: ZL3AI@ZL2BAU.#87.NZL.OC
To : APRDIG@WW
Message: 19
Date: Mon, 9 Oct 2006 10:56:47 -0400 (EDT)
From: "Bob Bruninga " <bruninga_at_usna.edu>
Subject: Re: [aprssig] Re: D7 and ITEM
>Bob, the documentation I've found is... confusing at best
>about the timestamp in OBJECT. Some places say optional,
>some places say not - which is it?
The time stamp is required.
But if the object is a permanent one that is never changing, then I
receommend that a time-stamp of 111111z be entered to indicate that the
field is not used. This is because some programs reject a 000000z time
stamp.
Bob
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Message: 20
Date: Mon, 9 Oct 2006 11:06:15 -0400 (EDT)
From: "Bob Bruninga " <bruninga_at_usna.edu>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
>I wish the FCC would come along and declare the
>future of APRS will be on 440 at 9600 baud,
Depends on what one thinks APRS is.
This clamor for 440 at 9600 baud flies in the face of physics if you want
good general coverage. VHF is 9 dB better than UHF for omni antnenas (think
mogbiles) AND it has less multipath and fades.
So APRS at UHF may have practical applications, but serving as a general
distribution it will never be as "good" as VHF. SUre all those problems
can be fixed with 3 times more digis to cover the same area, but I doubt it
will ever be practical for general coverage like VHF.
Bob
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Message: 21
Date: Mon, 09 Oct 2006 11:04:07 -0400
From: John Mc Hugh <johnk.mchugh_at_att.net>
Subject: [aprssig] ARISS
Did I miss a posting?
What has happened to ARISS?
Looking at the web page the last stations to contact it were 40 days ago
John, K4AG
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Message: 22
Date: Mon, 09 Oct 2006 10:29:32 -0500
From: Gregg Wonderly <gregg_at_wonderly.org>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
Bob Bruninga wrote:
...
>VHF is 9 dB better than UHF for omni antnenas (think mogbiles) AND
>it has less multipath and fades.
>
>So APRS at UHF may have practical applications, but serving as a
>general distribution it will never be as "good" as VHF. SUre all
>those problems can be fixed with 3 times more digis to cover the
>same area, but I doubt it will ever be practical for general
>coverage like VHF.
UHF does much better in structure penetration and requires a smaller
antenna system for the same gain (not power). 9 db of gain can be realized
with a stacked collinear about the same height as a 5/8s wave mobile VHF
antenna (which is 6b of gain). In the end, if antenna and gain is the
problem, the answer is more antenna, or better yet (for density
diversification), more digis. The "better" coverage of VHF is, in fact,
the bigger problem the current APRS network has.
Cellular and wide area network technologies use higher frequencies and
lower power to simplify life and create a more dependable system, not to
cause themselves to spend more money on more cell sites.
RF spectrum is finite. Space in the universe is infinite.
Gregg Wonderly
W5GGW
------------------------------
Message: 23
Date: Mon, 9 Oct 2006 09:43:43 -0600
From: Joel Maslak <jmaslak-aprs_at_antelope.net>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
On Oct 9, 2006, at 9:29 AM, Gregg Wonderly wrote:
>UHF does much better in structure penetration and requires a smaller
>antenna system for the same gain (not power). 9 db of gain can be
>realized with a stacked collinear about the same height as a 5/8s
>wave mobile VHF antenna (which is 6b of gain). In the end, if
>antenna and gain is the problem, the answer is more antenna, or
>better yet (for density diversification), more digis. The "better"
>coverage of VHF is, in fact, the bigger problem the current APRS
>network has.
I'll add that there will be less chance of corrupted packets from noise at
9600, since the packet is on the air a shorter amount of time. Remember,
one bit of corruption in a packet results in a lost packet!
I'm planning a test in a month or so on this. I'm going to set up a UHF
station next to my VHF IGate, and compare coverage. Of course it's not
possible to have a 100% fair test - audio levels will surely be set
differently, the VHF J-pole I use at home won't work for the UHF station so
the antennas will be different, etc. But it should give us a clue on
whether or not the difference is significant. One test disproves 1000
theories.
As for large coverage being the bigger problem that VHF has, speak for your
region. :) Wyoming has some very high digis that cover tens of thousands
of square miles - which are very handy for travelers and others. Yet,
there are relatively few collisions and such here, due to low density of
users (even with the occasional Texas station using a WIDE7-7 path, which
covers probably 250,000 square miles around here). It's not the coverage
that's the problem, it's the number of users in the collision domain and
the size of the aloha circle vs. digipeater location and user paths.
------------------------------
Message: 24
Date: Mon, 09 Oct 2006 08:43:51 -0700
From: "Stephen H. Smith" <wa8lmf2_at_aol.com>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
ddobbins_at_gmail.com wrote:
>
>Manufacturers should support this by focusing their product
>development, and lower their costs of 9600 baud equipment. A KPC-9+
>UHF only TNC would be great, for about $150,
And how is Kantronics supposed to insure that the TNC will only be used
on UHF ??? If it was this cheap, I'm sure some would also (horrors)
be used on 2M.....
>while the KPC-9612+ at
>$250, not $380, would be equally vundervas!.
As would be a D700 for $200 or a TS-200 for $500, but realistically it
just isn't going to happen, especially for products sold into a low
production-volume niche market.
--
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com
NEW! JavAPRS Filter Port 14580 Guide
http://webs.lanset.com/wa8lmf/aprs/JAVaprsFilters.htm
UI-View Misc Notes and FAQ
http://webs.lanset.com/wa8lmf/aprs/UIview_Notes.htm
"APRS 101" Explanation of APRS Path Selection & Digipeating
http://webs.lanset.com/wa8lmf/DigiPaths
Updated "Rev G" APRS http://webs.lanset.com/wa8lmf/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:
------------------------------
Message: 25
Date: Mon, 9 Oct 2006 11:47:49 -0400
From: Steve Dimse <steve_at_dimse.com>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
On Oct 9, 2006, at 11:29 AM, Gregg Wonderly wrote:
>Cellular and wide area network technologies use higher frequencies
>and lower power to simplify life and create a more dependable
>system, not to cause themselves to spend more money on more cell
>sites.
Actually, they do want a frequencies that allows more cell sites, or at
least they want one that allows them to match the cell sites to the demand.
If you have a hundred users in a city, then a VHF frequency allows you
cover the city with a handful of cells, or even a single one. If you have a
million users, you need each frequency to be reused multiple time in the
same metro area. For that, higher frequencies with their greater path loss
are ideal.
Does APRS have a hundred users or a million in a city? Do you want one or
two digis, or a hundred mini-digis?
As long as the APRS answer is a hundred users, 2 meters is the "best"
answer.
Steve K4HG
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Message: 26
Date: Mon, 9 Oct 2006 09:24:29 -0700
From: "VE7GDH" <ve7gdh_at_rac.ca>
Subject: Re: [aprssig] 9600b UHF APRS IS THE FUTURE OF APRS
Gregg W5GGW wrote...
>The "better" coverage of VHF is, in fact, the
>bigger problem the current APRS network has.
>
>Cellular and wide area network technologies use higher
>frequencies and lower power to simplify life and create a
>more dependable system, not to cause themselves to
>spend more money on more cell sites.
And Bob WB4APR had written earlier...
>VHF is 9 dB better than UHF for omni antennas (think mobiles)
>AND it has less multipath and fades. So APRS at UHF may have
>practical applications, but serving as a general distribution it will
>never be as "good" as VHF.
Good postings by both! I have been suggesting for a long time (ummm...
better let me re-phrase that; for a couple of years or so!) that we need to
operate more like the cellular network. Instead of more "big" digis up at a
higher elevation, we need more "small" digis at least in the populated
areas with less coverage. Perhaps densely populated areas could work on a
low powered UHF network for operation in the concrete jungle. The existing
VHF infrastructure could remain in place or be pruned a bit. Keep the high
elevation VHF digis for operation away from densely populated areas,
consider removing a few high elevation digis if they are causing more harm
than good, and encourage 1200 bps UHF APRS for the densely populated areas.
This concept would work better if the stations in the densely populated
areas reduced their power when they are in an area with a large number of
low elevation digis. The ideal situation would be radios that are both
frequency agile so they can move seamlessly between densely populated areas
with good UHF coverage and out in the boonies where they need to change
back to VHF and up the power a bit. Even better, the output power would
automatically adjust itself either based on the strength of received
signals (from digis only) or upon confirmation of being digipeated.
Lofty goals, and it won't happen overnight. At the very least, we could
work on moving some of he high elevation digis near populated areas to
lower elevations and encourage building of UHF digis in the same densely
populated areas. Users could be asked to stick to low power when needed.
These can all be done without fancy frequency agile radios that
automatically adjusted their power output.
I'm not putting down 9600 bps packet. I've never even owned a 9600 bps TNC
(until now... just received a beta TT4 the other day) so don't have any
first-hand experience with the vagaries of 9600 bps on RF, but I'm all for
developing equipment for faster and more robust packet connections. There
are those experimenting with 9600 bps packet, notably in the Seattle /
Puget Sound area, but for general use, it sounds like there are advantages
of 1200 vs 9600 and there are advantages on VHF vs UHF, but both will have
a place. It's just time & money, and the enthusiasm for development new
equipment. I'm hoping the commercial manufacturers don't abandon us, but
I'm increasingly getting the impression that development of "leading edge
RF communications" is again putting the ball back in our court instead of
leaving it up to the commercial manufacturers telling us what they can
provide.
73 es cul - Keith VE7GDH
--
"I may be lost, but I know exactly where I am!"
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