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ZL3AI > APRDIG 19.05.04 09:20l 167 Lines 6935 Bytes #999 (0) @ WW
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Subj: TAPR Digest, May 04, 6/6
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: DAMA was mentioned here Flexnet?
From: Jeff King <jeff@aerodata.net>
Date: Tue, 04 May 2004 18:29:11 -0500 (CDT)
X-Message-Number: 38
Quoting Brian Webster <bwebster@wirelessmapping.com>:
>networks together with flexnet/tcpip. The other good thing about flexnet is
>it's ability to run the kernel under dos on older computers. This could also
>be a disadvantage for remote digi sites as there are no stand alone
>tnc versions of flexnet.
At one time, I seem to recall a version of FlexNet that ran on something
called the RMC.... a german creation maybe with a 6800x class processor,
but it is real fuzzy and that is just from the back of the mind.
But I have (just about) given up on the TNC as an approach for network
nodes. Do check out the Mini-ITX web site:
http://www.mini-itx.com/
http://www.mini-itx.com/projects.asp
and this site which has a automotive class power supply for them:
http://www.mini-box.com/
It is amazing what folks are doing with the PC compatible mini mother
boards. In particular, the versions that are fanless.... no fan and the
processor is soldered to the board. One of those, coupled with a compact
flash to boot from.... a TNC in a box, abet a bit more expensive. But much
more flexiable.
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Subject: Re: RE: Long distance wireless APRS
From: Jeff King <jeff@aerodata.net>
Date: Tue, 04 May 2004 18:36:10 -0500 (CDT)
X-Message-Number: 39
Quoting Bill Vodall WA7NWP <wa7nwp@jnos.org>:
>You could try a pair of Metricom Ricochet modems. Slower (100 kbits)
>then the
>WiFi solutions mentioned but more power (1 watt spread specturm) and
>much cheaper.
Bill:
Whats the part number that I want to look for? Ever since I sold my FreeWave
modems I'd been needing something to replace them for quick wireless serial
links around the neighbor hood. I've never owned a Ricochet so I don't know
which one to bid on.
Thanks!!
Jeff wb8wka
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Subject: Re: Slotted ALOHA
From: Wes Johnston <wes@johnston.net>
Date: Tue, 04 May 2004 21:17:39 -0400
X-Message-Number: 40
Slotted aloha with two frequencies puts the tracker in a position of
transmitting blind... but at least the digipeater's output is on different
frequency cutting the effective channel load in 1/2. What if we did
something like that with MACA...
I realize I'm stretching Karn's idea of MACA a bit in my examples here, but
I am trying to make simple MACA work with relay digipeaters, therefore I've
altered the MACA protocol a little by allowing CTS packets to make other
stations holdoff... Karn says CTS will be matched with a RTS packet and the
RTS packet will cause other stations to hold off... I'm proposing something
a little different.
Here's how MACA works ...
my tracker TX's a CTS frame with the number of bytes (or 10's of
milliseconds) I wish to TX indicated.
the digipeater responds by digipeating that same CTS frame and the number
of bytes (or mS) my station will TX.
Anyone hearing that packet will shutup for that many milliseconds. If my
station sees the digipeated CTS packet it knows that it was heard by the
digipeater and everyone around the digipeater and knows that it must be OK
to transmit.
My tracker TX's my data.
Subsequent digipeats of my packet may or may not use this method of asking
everyone else to hold off. After all, the digipeater can hear better than
anyone and is in a very good position to talk over the top of any other
digipeaters in so far as the local home and mobile network users are
concerned. If I'm routing a message packet to a *specific* place, then it
would be nice to use this method combined with a point to point retry
handoff to make sure that packet gets to the next digipeater.
If I don't get into the digipeater with my CTS packet after XX number of
tries, I back off and try again later when the band isn't so busy.
*****************************************************************************
Now, If we extend the MACA idea across to frequency agile radios...
my tracker TX's a CTS frame with the the number of bytes I wish to TX
indicated AND the QSY request bit set.
the digipeater responds with a RTS frame and a frequency assignment
Only my station pays attention to the RTS packet. Since it indicates that
my station is to QSY, there is no need for any stations to inhibit TX on my
behalf.
My tracker QSYs, TX's my data and returns to the digipeater's output
frequency.
Note that as I move from area to area, different digipeaters may use
different input frequencies... these are made known to my tracker as needed
when the digipeater responds to my CTS packet.
Of course two trackers can transmit long'ish packets on two different
digipeater input frequencies at the same time.... let's say that a "well
setup" digipeater has 4 input frequencies (one on the customary APRS
frequency, and 3 others). It should never assign the customary aprs
frequency, but rather roll around the other 3 when it dishes out channel
assignments.
Now if my station needs to transmit a 4 second long packet, and the guy
down the street needs to transmit a 10 second long packet, I'll ping the
digipeater with a CTS, and I will assign me frequency 2. A few mS later,
the guy down the street pings the digipeater with a CTS also. He is
assigned frequency 3. Now we both arrive on frequency 2 and 3 at nearly
the same time, and transmit our packets, but since we are on different
frequencies and the digipeater node has multiple inputs, it copies both of
our packets. Note that if the digipeater hears activity on any of it's
input frequencies at a given time it will not assign that frequency via a
RTS packet.
This is like trunking for APRS and a combination of Phil Karn's MACA and
Bob Bruninga's "two eared one mouth" digipeater idea. ( I gotta give
credit where it's due).
Wes
----------------------------------------------------------------------
Subject: Re: OT? Garmin E-Trex setting
From: "Alton" <n5psp@n5psp.org>
Date: Tue, 4 May 2004 21:43:22 -0500
X-Message-Number: 41
Only problem is I also use that same E-trex for geocaching and other things
where it can't have ribbon cable dangling out from it (at least till I win
the lottery & can get a Summit or Vista to run around in the field with -
LOL)
I've observed the problem when running battery only with the data cable but
no power/data cable as well. It seems that it "detects" phantom power that
then when that goes away it starts an auto-shutdown sequence.
Since my first post, I've waded through a few hundred Google hits and
stumbled on some later firmware upgrades, one of which had a line about
"improved external power detection". So I might try that at some point after
backing up all the waypoints and user map data.
---
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