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ZL3AI > APRDIG 05.01.07 23:55l 251 Lines 8602 Bytes #999 (0) @ WW
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Subj: [APRSSIG] Vol 31 #4, 4/4
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Sent: 070105/2239Z @:ZL2BAU.#79.NZL.OC #:25293 [Waimate] $:9488-ZL3AI
From: ZL3AI@ZL2BAU.#79.NZL.OC
To : APRDIG@WW
Message: 26
Date: Wed, 03 Jan 2007 15:11:18 -0800
From: "Stephen H. Smith" <wa8lmf2_at_aol.com>
Subject: Re: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
bruninga_at_usna.edu wrote:
>>The transmitting of raw NMEA strings over the air...
>>... is highly discouraged in California. Raw NMEA
>>... occupy up to TEN times more air time than the
>>most compact encoding format for APRS (Mic-E).
>>
>
>A little caution and explanation with that advice...
>
>1) True, it is 10 times longer, but when you include the packet
>overhead this is more like only a factor of 2 longer.
>
>2) The KPC-3+ TNC tracker that sends raw NMEA can actually
>produce less QRM, because it can be set to PROPORTIONAL PATHING.
This accomplishes nothing in Southern California where all the digipeaters
enforce SINGLE HOP no matter what path is set into the tracker. All you
are doing is transmitting longer packets that:
1) Occupy more air time
2) Are much more likely to get trashed due to congestion on the saturated
channel here.
--
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com --OR-- http://wa8lmf.net
NEW! TNC Test CD
http://wa8lmf.net/TNCtest
JavAPRS Filter Port 14580 Guide
http://wa8lmf.net/aprs/JAVaprsFilters.htm
"APRS 101" Explanation of APRS Path Selection & Digipeating
http://wa8lmf.net/DigiPaths
Updated "Rev G" APRS http://wa8lmf.net/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:
------------------------------
Message: 27
Date: Wed, 3 Jan 2007 15:25:19 -0800
From: "Scott Miller" <scott_at_opentrac.org>
Subject: RE: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
I think this is really my main objection to the proportional pathing scheme.
Even up the coast here, you don't need more than 2 hops to get all over.
There's really not much benefit unless you want to be seen in Arizona. And
users who don't understand it are probably more likely to crank their rate
up higher when they don't see their packets getting in as often as they
expect. Even with SmartBeaconing I have to remind users that when they're
sitting still, bench testing a unit, it's going to have a low transmit rate.
Scott
N1VG
------------------------------
Message: 28
Date: Wed, 3 Jan 2007 20:44:49 -0700
From: Joel Maslak <jmaslak-aprs_at_antelope.net>
Subject: Re: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
On Jan 3, 2007, at 4:03 PM, Robert Bruninga wrote:
>1) True, it is 10 times longer, but when you include the packet
>overhead this is more like only a factor of 2 longer.
And still *MUCH* shorter with a decent radio than the smallest possible
D700 packet - no half second TX Delay!!! (at least until the first digi)
------------------------------
Message: 29
Date: Thu, 4 Jan 2007 07:05:15 -0600
From: Jason Winningham <jdw_at_eng.uah.edu>
Subject: Re: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
On Jan 3, 2007, at 9:44 PM, Joel Maslak wrote:
>And still *MUCH* shorter with a decent radio than the smallest
>possible D700 packet - no half second TX Delay!!! (at least until
>the first digi)
Well, digis are not only responsible for the majority of on-air copies of
the packet, they also cover vastly more _area_ due to the fact they
typically have much larger antenna height _and_ higher gain. Therefore
they use far more available bandwidth over the life of the packet than a
D700 operating mobile, even accounting for the abominable 500ms txdelay.
NMEA strings are bandwidth hogs, pure and simple. They are over twice as
long, including AX.25 headers, and they convey less information.
Drop $30 on an opentracker. No, it doesn't decode, but if you are
transmitting NMEA sentences with a TNC you're not actually looking at any
received data anyway. OK, maybe a couple of hardcore APRS folks may look
at raw APRS packets and get something out of it, but if you've got a GPS
tied to the TNC serial port then you are not using an application to decode
packets - e.g., you're operating just like a dumb tracker and you're
wasting more bandwidth and using more expensive (and bulky) equipment to do
it.
If you're not going to decode anyway then get an OT, set the RX sensitivity
to avoid collisions, and save some bandwidth.
-Jason
kg4wsv
------------------------------
Message: 30
Date: Thu, 4 Jan 2007 07:14:26 -0800
From: "EXT-Maetta, John" <john.maetta_at_boeing.com>
Subject: RE: [aprssig] Help with Interfacing a GPS to Kantronics KPC-3
'morning Earl,
I will look into that, but I have tried swapping data pins from the GPS to
the TNC with out any luck. But I will try your suggestion again. You said
it right enough for me to get your meaning. DTE vs DCE, still confuses me
to this day : )
John
-----Original Message-----
>From: Earl Needham [mailto:needhame1_at_plateautel.net]
>Sent: Wednesday, January 03, 2007 2:48 PM
>To: TAPR APRS Mailing List
>Subject: RE: [aprssig] Help with Interfacing a GPS to Kantronics KPC-3
>
>At 03:41 PM 1/3/2007, EXT-Maetta, John wrote:
>>I use my laptop's serial port with Hyperterminal and cable to 'simulate
>
>>the GPS' by sending the captured GPS $GPxxx strings to the KPC.
>>This is the same cable, laptop and terminal program I use to set the
>>KPC up.
>
>But what I'm trying to say, and it may be more basic than what
>is needed here, is that the TNC is configured the same as a modem --
>what do they call that??? DCE or something? And it appears your GPS is
>configured the same way, because you can see the data from the TNC (the
>"sign on message") and you can also see the strings from the GPS. This
>means that data FROM each is on the same pin, when it should, in fact,
>be on different pins. The GPS should emulate your computer, not the
>TNC.
>
>Somebody jump in here, I know what I'm trying to say, but I
>don't have the right words to say it!
>
>7 3
>Earl
------------------------------
Message: 31
Date: Thu, 4 Jan 2007 07:38:52 -0800
From: "EXT-Maetta, John" <john.maetta_at_boeing.com>
Subject: RE: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
'morning Bob,
Yes, that is what I am receiving from the PIC-E. Just a few bytes of data.
Holy Cow!. Maybe, the PIC-E is working and I didn't have a clue as to what
data I should have been receiving. I assumed it would be a plain text GPS
co-ordinate parsed from the $GPRMC string.
If I remember correctly from my weekend trials, I would route the PIC-E
audio output into the KPC-3 audio input and would decode something like
this from the KPC-3: 3RYR26,RELAY,WIDE-1,WIDE-2,0]]06/. Then my beacon text
would follow.
Do I need to run APRS software to decode this data from the KPC-3?
73,
John
N6VMO
------------------------------
Message: 32
Date: Thu, 04 Jan 2007 10:25:40 -0600
From: Mark Earle <wa2mct_at_mearle.com>
Subject: Re: [aprssig] Help with Interfacing a GPSto Kantronics KPC-3
EXT-Maetta, John wrote:
>'morning Bob,
>
>Yes, that is what I am receiving from the PIC-E. Just a few bytes of
>data.
>
>Holy Cow!. Maybe, the PIC-E is working and I didn't have a clue as to
>what data I should have been receiving. I assumed it would be a plain
>text GPS co-ordinate parsed from the $GPRMC string.
>
>If I remember correctly from my weekend trials, I would route the PIC-E
>audio output into the KPC-3 audio input and would decode something like
>this from the KPC-3: 3RYR26,RELAY,WIDE-1,WIDE-2,0]]06/. Then my beacon
>text would follow.
>
>Do I need to run APRS software to decode this data from the KPC-3?
>
>73,
>
>John
>N6VMO
It's easier, but the aprs spec would let you hand -decode this, but it
"looks" like a mic-e packet to me. That's why Mic-e is useful compared
to sending raw NMEA strings out on the air - very comressed.
I run a pic E... if you findu my -9 the look at raw data you can see
what mine looks like.
This is a typical one, with me in Corpus Christi, TX:
Raw packet: WA2MCT-9>RW4Q8T-5,KD5UJY*,KD5UJY-11*,WIDE2,qAo,K5COD:`}2Vl#Hk/
The k/ indicates my icon is a red truck.
--
) ) de WA2MCT Mark
( ( Echolink 99190 Grid Square EL17HQ
) ) You will be assimilated... oooh, coffee!!
_|****| http://www.findu.com/cgi-bin/find.cgi?wa2mct-7 Home
( | | http://www.findu.com/cgi-bin/find.cgi?call=wa2mct-9 Mobile
`|____| wa2mct_at_mearle.com wa2mct_at_juno.com wa2mct_at_arrl.net
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