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ZL3AI > APRDIG 18.05.04 21:22l 296 Lines 11555 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: Attn: Armchair Lawyers
From: Jeff King <jeff@aerodata.net>
Date: Mon, 03 May 2004 14:24:06 -0500 (CDT)
X-Message-Number: 33
Quoting Steve Dimse <k4hg@tapr.org>:
>On 5/2/04 at 10:47 PM Jeff King <jeff@aerodata.net> sent:
>
>>Now, I will express my "opinion". I make a good faith effort to see if the
>>channel is clear before I transmit. Yes I could interfere with someone, but
>>the operative word is "good faith". This is in keeping with the spirit of
>>97.101(a). The rules are not absolute, but they are clear about following
>>good engineering practices.
>>
>Good faith does not appear in the rules.
Your right, it does not. It only can mitigate. So I can get you on focus,
lets change the band and application.
I'm on HF, running SSB voice. Two cases:
1. I listen first, if I hear a QSO, I hold off, if I don't, I make my call.
Now, because of the HF skip zone, I don't hear someone, and interfere with
them.
2. I need to put out the club bullitin on HF (legal one way transmission),
I turn the speaker down so I don't hear the QSO in progress, and make the
bulletin announcment.
In both cases, a QSO is interferred with. But in case one, the person made
a good faith effort to avoid interference, by following good amateur
practices as defined in 97.101(a).
When Uncle Charlie comes a knocking on your door, who would you want to be?
>If we can move beyond the legal
>argument, which I agree is a decision each person need to make on their
>own, all
>that is left is "97.101 General standards. (a) In all respects not
>specifically covered by FCC Rules each amateur station must be operated in
>accordance good engineering and good amateur practice."
>
>My opinion is good amateur practice is to do what is practical to
>limit interference.
Do we disagree here? I think not.
>I think you would agree that a receive antenna hundreds of feet
>higher than my tranmit antenna would do a great deal to decrease the
>amount of interference a tranmitter causes on 144.39.
No, I wouldn't. APRS should be considered a cellular system... your transmit
power should be carefully matched to your expected coverage. As such, your
recieve antenna should be at about the same height as your transmit antenna.
You also should use the least amount of power required to complete the
communications (which, BTW, is specifically in the rules).
>The argument for deaf transmitting is the same...the hardware does not
>support listening.
I'm not aware of a single transmit only tracker that does not have a CSMA
input, even the ones with a transmitter only have the input. The manfacturers
put them their for a reason.
>However, I maintain a pocket tracker running 300 mw to a modest
>antenna beaconing a position report every 5 minutes using time-slotting
>is good
>amateur practice, in fact much better amateur practice than a lot of
>what happens now on 144.39. Do you disagree?
You mean used as it was intended? In your pocket, with a rubber duck? Yes, I
have already said it wouldn't cause much impact on the network.
>but I say it is
>wrong to dismiss all deaf transmitting as bad engineering or amateur
>practice.
But that is not what I said. It has nothing to do with the manufacturers.
....I'm not aware of a single tracker that doesn't have a CSMA input on it.
The point being, no-one is going to look out for you. Each individial amateur
needs to make sure they are in compliance with 97.101(a).
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Subject: Re: Attn: Armchair Lawyers
From: Steve Dimse <k4hg@tapr.org>
Date: Mon, 3 May 2004 15:44:31 -0400
X-Message-Number: 34
On 5/3/04 at 2:24 PM Jeff King <jeff@aerodata.net> sent:
>1. I listen first, if I hear a QSO, I hold off, if I don't, I make my call.
>Now, because of the HF skip zone, I don't hear someone, and interfere with
>them.
>
>2. I need to put out the club bullitin on HF (legal one way transmission), I
>turn the speaker down so I don't hear the QSO in progress, and make the
>bulletin announcment.
>
>In both cases, a QSO is interferred with. But in case one, the person made a
>good faith effort to avoid interference, by following good amateur practices as
>defined in 97.101(a).
"Good Amateur Practice is not defined in 97.101(a) or any other part of the
rules. That section just says you need to do it.
The two examples you give have no bearing on this issue. HF voice is able to
carry a single conversation on a channel. The is no provision for channel
sharing. Packet, on the other hand, has the built-in expectation of collision.
This difference leads to different "good amateur practice" on the two modes,
what constitutes good amateur practice on one mode will not necessarily carry
over to another.
Steve K4HG
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Subject: Re: REVISED Updated APRS Symbols posted
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Mon, 3 May 2004 13:12:52 -0700
X-Message-Number: 35
I have received several comments, list posts, etc about the revised
symbol set I posted yesterday (Sunday 2 May 04). In response, I have
made some updates to my revised APRS symbol set at:
http://members.aol.com/wa8lmf/aprs/APRS_symbols.htm
Again, once I get the final round of updates, etc, I will be placing a
downloadable zip file containing the revised symbols images in BMP
format and a matching UIview.INF file on my website.
[ Read down for more comments; I am answering several posts at once in
this message. ]
Spider wrote on 5/2/2004, 6:22 AM:
>Stephen,
>
>Your Incident Command Post symbol is incorrect.
>
>Jim, WA6OFT
>What I noticed is that your
>ICP (Incident Command Post) and your MODIS Earth Observation symbols are
>incorrect.
>
>If you do not know what the standard ICP symbol is, I'll send it to you.
It's not mine -- it's the original one from the UI-View set. Still
waiting for someone to either point me to a website that shows the
correct one or email me an image off-list....
Christensen, Eric wrote on 5/3/2004, 10:58 AM:
>Has anyone made pictures for UI-View for the new symbols (see
>below)?
>
>29 Jan 2004: Reviewed ALL symbols in the spec. Here are all additions:
> \& = is not just HF, but ANY GATEWAY with overlay character
> /) = Wheelchair (Handicapped) useful in Marathons (blue and white)
> \) = Firenet MEO symbol (MODIS Earth observation)
> \/ = Waypoint (destination) a RED dot showing intended destination.
> Uses special processing to draw a line from a mobile to his
> destination. This was proposed 5 Jan 2004
> /L = Logged-ON user. (A PC symbol showing someone on APRS-IS)
> /l = Laptop (lower case L) (looks like a laptop)
> /c = Incident Command Post
> \y = Skywarn (black tornado on orange background with white surround)
> /z = Shelter (with overlay) (A red house with peaked roof)
>
>I know SKYWARN, Incident Command Post, and the MEO symbol are already in
>UI-View, but the others aren't. I'm no artist but I might be able to
>handle the red DOT for the destination symbol.
1) I assume the \& GATEWAY symbol should be marked as an overlay-able
symbol (highlighted in yellow) in my alpha-to-symbol mapping presentation.
2) Wheel Chair - already in my new set
3) Firenet MEO -- waiting for someone to send me an image of this
4) Waypoint symbol -- how does this differ from the red dot at the same
position in the primary set?
5) /L "Logged-On User" -- already added to my revised set
6) /l "Laptop" -- A Google image search quickly yielded a suitable
icon that I downsized to 16x16 pixels and added to the set.
7) /c "ICP" -- see above, waiting for someone to send me an image of this
8) \y "Skywarn Tornado" -- drew one in Microanglo icon editor and
added it to the set, take a look. Is this supposed to be overlay-able??
9) /z "Shelter (with overlay)" (A red house with peaked roof) Changed
my black outline on white to solid red but how is this supposed to be
overlaid in the primary set?? (Or was this a typo andshould actually be
in the corresponding position in the secondary set?)
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff http://members.aol.com/wa8lmf/aprs
Personal APRS Webserver http://members.aol.com/wa8lmf/webserver
----------------------------------------------------------------------
Subject: Re: Attn: Armchair Lawyers
From: Jeff King <jeff@aerodata.net>
Date: Mon, 03 May 2004 15:18:25 -0500 (CDT)
X-Message-Number: 36
Quoting Steve Dimse <k4hg@tapr.org>:
>On 5/3/04 at 2:24 PM Jeff King <jeff@aerodata.net> sent:
>
>>1. I listen first, if I hear a QSO, I hold off, if I don't, I make my call.
>>Now, because of the HF skip zone, I don't hear someone, and interfere with
>them.
>>2. I need to put out the club bullitin on HF (legal one way transmission), I
>>turn the speaker down so I don't hear the QSO in progress, and make the
>>bulletin announcment.
>>In both cases, a QSO is interferred with. But in case one, the person made a
>>good faith effort to avoid interference, by following good amateur
>>practices as defined in 97.101(a).
>"Good Amateur Practice is not defined in 97.101(a) or any other part of
>the rules. That section just says you need to do it.
OK, I don't understand, do we have a problem with doing this?
>Packet, on the other hand, has the built-in expectation of collision.
And so does HF. It is called "skip zone". Packet also has a mechnism called
CSMA, that allows it to try and listen to the channel first before
transmitting. Humans have a ear, which lets them listen to the channel first
before transmitting. CSMA packet, as best it can, uses CSMA to reduce the
expectation of collison.
Or are you saying 144.39mhz APRS operates under pure aloha?
You know, everything we are discussing has factual answers and responses. The
probem is we just don't have the facts. Here are some descriptions of packet
radio channel access methods for you:
http://en.wikipedia.org/wiki/ALOHA_network
Now, one fact we are missing that we need to comply under 97.101
What is the channel access APRS uses?
I was under the impression it was CSMA. From what I am hearing from you, it
would seem ALOHA.
If it is CSMA, you need to try and listen first, and yes, collisions
occasionally will occur. If it is ALOHA, you can just blast the packet out
with no regard for anyone else on the channel. Collisions will increase
dramatically.
Defining the channel access method for APRS, will lead to the correct
application of 97.101. As I said, until I hear otherwise, I will assume
CSMA and approach 97.101 from this perspective.
>This difference leads to different "good amateur practice" on the two modes,
>what constitutes good amateur practice on one mode will not necessarily
>carry over to another.
Again, then what mode should 144.39 APRS be operated under then? Pure Aloha or
CSMA? That is the defining question.
In other words:
1. Should you try and listen first before you transmit on a mixed use channel?
(as CSMA dictates)
2. Should you not bother to listen first before you transmit on a mixed use
channel? (as one would in a aloha network)
Put in the terms of ALOHA vs. CSMA, this is a black and white question, if the
opinion of academia means anything to you.
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