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ZL3AI > APRDIG 12.05.04 09:54l 229 Lines 9193 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Apr 22, 6/10
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: Kenwood MObile APRS
From: "KC2MMi" <kc2mmi@verizon.net>
Date: Thu, 22 Apr 2004 15:22:40 -0400
X-Message-Number: 31
>>>"KC2MMi" <kc2mmi@verizon.net> 4/21/04 2:09:47 PM >>>
>With APRS now even a TT3 can support sending a status
>string once every ## transmissions. And both a primary
>and secondary configuration, with totally separate parameters.
BB: [[Yes? So does the D7. It has 3 different cofigurations and the
D700 has 5. And both can set the status rate separately...]]
Yes Bob. I was talking about the larger context of how to use a new APRS
spec, with new packets and new data in them, without obsoleting the old
equipment. Apparently I didn't make that clear.
The D7's multiple configurations are irrelevant to this, I'm suggesting
sending complete alternate packets, no just alternate status text. The D7,
btw, is also limited to a 45 character message and has no ability to
automatically alternate between any strings or settings.
I have no idea what the D700 does, as I've said previously.
I was and am suggesting, as Scott understood, that you can keep 100%
backwards compatibility with the obsolete devices by having the new ones
send "APRS1.0" for their packet on the first transmission, followe by an
"APRS3.0" packet on the second one, and then alternating between them.
Yes, this can be a bandwidth problem IF operators decide to double their
transmission rate. That's a decision each would make based on what equipment
they were locally supporting. Ideally, and especially for fixed bases, they
would not increase the rate since all newer stations would still see ALL the
packets with all the data, and only the obsolete equipment would see half
(old format only) the information. I trust you get the idea and I don't have
to go further on that?
I also said that I don't know what an existing APRS station does if a packet
is too long, and that provides another way to skin this cat. An "APRS3.0"
packet could simply be extended to 512 bytes, keeping the first half as it
is now, but adding 255 bytes plus an end mark (256 total) to the existing
packet. IF the existing equipment simply dropped the extra data....this
would allow new equipment to simply extend the packet format.
The end mark is suggested because who knows...someone might want to extend
it even further, in an open and extensible custom scheme. There's no reason
for a fixed length, except to save the overhead of an end mark, is there?
APRS is like the classic picture of a glass with water in it. The question
is not whether it is half filled or half empty. The glass itself tells reams
about the technology level of the user and begs the larger questions of
whether there's a busboy out there neglecting his station. Or, a happily
satiated drinker and a water pitcher just out of frame. The glass presents
all those questions, whether it is half empty or half full irregardless.
Here we are arguing about the size of a water glass, and whether larger
glasses will create a need to stack them on different trays.
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Subject: Re: From: "KC2MMi" display the position data?
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Thu, 22 Apr 2004 15:27:03 -0400
X-Message-Number: 32
Bob?
>>>"KC2MMi" <kc2mmi@verizon.net> 4/21/04 1:57:36 PM >>>
>>Name me ONE thing that you think the Kenwood
>>Mobile Radio APRS capability is "holding back"
>...Well, two things if you can do them both.
>When the D7 is used with a headless GPS (i.e. hockey puck)
>can you make it display the position data and EPE
>data from the GPS?
Yes, easy. Buy a GPS with a display...
>All I want is to see the same DDD.MM.mmm that my
>GPS is putting out, on the radio.
Easy, just look at your GPS which should display that data easily...
The D7 is designed to be connected to a GPS that has a display if you want
to SEE the GPS data... That is not the fault of the radio if you chose to
buy a GPS with no display...
Bob
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Subject: Re: APRS greater precision
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Thu, 22 Apr 2004 15:38:09 -0400
X-Message-Number: 33
>>>"KC2MMi" <kc2mmi@verizon.net> 4/22/04 11:39:25 AM >>>
>Look on the bright side: A radio like the THD7 is already
>obsolete, it DOES NOT support the existing APRS capabilities.
Interesting comment from someone who doesnt own one. And by that kind of
tight definition, anything that leaves the factory is instantly obsolete
the day the first one comes off the assembly line.
sigh...
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Subject: Re: APRS greater precision
From: "Curt, WE7U" <archer@eskimo.com>
Date: Thu, 22 Apr 2004 12:49:40 -0700 (PDT)
X-Message-Number: 34
On Thu, 22 Apr 2004, Robert Bruninga wrote:
>>>>"KC2MMi" <kc2mmi@verizon.net> 4/22/04 11:39:25 AM >>>
>>Look on the bright side: A radio like the THD7 is already
>>obsolete, it DOES NOT support the existing APRS capabilities.
>
>Interesting comment from someone who doesnt own one.
>And by that kind of tight definition, anything that leaves the factory
>is instantly obsolete the day the first one comes off the assembly
>line.
>
>sigh...
Anything with fixed-firmware is pretty close to that, unfortunately.
I got a few flash updates to my main hand-held GPS for a while, but can't
get them anymore 'cuz it is too old. I will have to buy a new one, but as
a bonus I'll get a lot more features in the new one, for a lot less money
than I originally paid for the old one.
By providing flash upgrades for a few years, they extended the useful
lifetime of the product immensely. I'm not upset that I'll have to buy a
new one soon, 'cuz I got my money's worth.
I've done the same sort of flash updates to other items. Usually to fix
bugs, sometimes to add new features.
Things like digipeaters and APRS radios could benefit immensely from this
(now old) technology of flash upgrades.
--
Curt, WE7U archer at eskimo dot com
Arlington, WA, USA http://www.eskimo.com/~archer
"Lotto: A tax on people who are bad at math." -- unknown
"Windows: Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me: I picked the coordinate system!"
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Subject: Re: Additional thoughts on the great debate....
From: "Robert Bruninga" <bruninga@usna.edu>
Date: Thu, 22 Apr 2004 15:52:18 -0400
X-Message-Number: 35
>>>"Curt, WE7U" <archer@eskimo.com> 4/22/04 11:47:27 AM >>>
>Ambiguity:.. I suspect it will get dropped again.
>Perhaps there's a good reason that this one keeps
>popping up every few years Bob?
Yep, those people who were asleep in their middle school science class when
they were supposed to learn about precision, accuracy, and significant
digits will never get it... So we have to go over it again and again...
>Precision: Bob has changed his mind with respect to promoting
>Base-91 Compressed posits (which are in the ratified spec), so that
>only leaves us NMEA posits with more digits after the decimal point
>to support higher precision,
I have proposed the !XYZ! format which is backwards compatible solution for
all existing clients and gives precision to one foot for all future APRS
applications..
>I'd really like to see the Base-91 compressed posits supported
>exactly as listed in the spec, for posits, objects, and items.
I simply dont receommend it because it is not FULLY implemented and
therefor UNUSABLE in a standard communications system where the lack of
complete implementation in ALL end users would mean some people see the
info and some dont... It is impossible to do comunications planning with
come-as-you are stations without having a standard that is properly
implemented.
>Xastir fully supports Base-91 compressed posits, objects,
>and items, exactly as specified in the APRS Spec. I can
>do useful things with those during SAR missions, and
>cannot do those things at all without the compressed mode.
Yes, you can, but only with the other handful of XASTIR users (out of
23,000 total other users)...
>Perhaps it is an advantage after all, as I can
>create compressed objects/items at will and post them on the map,
>and few others can see them/manipulate them.
Yes, very few... So it does not seem that this is something that you would
want to force on APRS, and that is known incompatibilities?
Bob
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Subject: Pocket Tracker Question for the group
From: "Sadowski, Allan" <allan.sadowski@ncshp.org>
Date: Thu, 22 Apr 2004 16:03:33 -0400
X-Message-Number: 36
I was looking at the schematic for the pocket tracker (looks good
Gentlemen)... and I must confess that one thing doesn't make sense to me...
I see the microcontroller controls a PTT LED.. but I don't see how the PTT
actually controls the RF section.
How does the RF section know not to transmit... when no modem tones need to
go over the air?
TNX in advance..
ALOHA
AH6LS
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