| |
ZL3AI > APRDIG 03.10.03 09:36l 143 Lines 5852 Bytes #999 (0) @ WW
BID : 2068-ZL3AI
Read: GUEST
Subj: TAPR Digest, Sep 30, 11/16
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<WB0TAX<N1UAN<ZL2BAU<ZL3VML
Sent: 031002/1441Z @:ZL3VML.#80.NZL.OC #:9565 [Chch-NZ] FBB7.00i $:2068-ZL3AI
From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: Cheap GPS receivers / RS232 / Digitraveller
From: Dale Blanchard <wa7ixk@arrl.net>
Date: Tue, 30 Sep 2003 13:45:43 -0700
X-Message-Number: 45
Scott Miller wrote:
>I'm pretty sure it does, as long as you've got the memory to hold the maps.
>Not sure if it comes with the right cable, though.
Mine came with three cables. Non of them fit my Palm IIIxe. I was able
to find one of each, serial and pda. One is going to be taken apart to
use with my Tini track and old Yaesu handheld.
----------------------------------------------------------------------
Subject: Re: Take Control of your DIGI part 4
From: "Scott Miller" <scott@opentrac.org>
Date: Tue, 30 Sep 2003 13:51:01 -0700
X-Message-Number: 46
Henk, what are DIGI_NED's requirements for RAM and program space? Is there
any chance that it could be squeezed into an embedded platform, like maybe a
KPC-3? How much OS-dependent stuff has it got?
Scott
N1VG
----------------------------------------------------------------------
Subject: RE: Cheap GPS receivers / RS232 / Digitraveller
From: "JBCrafts" <jbcraft@adelphia.net>
Date: Tue, 30 Sep 2003 16:49:17 -0400
X-Message-Number: 47
I just picked up ONE (PDA version) and going after two more tomorrow...
There are perhaps 20 in the Cincinnati area.... FIVE in Harrison Ohio
(border of IN/OH on I-74)
now, where did I leave my solder pencil ......
Bob K8YS
----------------------------------------------------------------------
Subject: RE: Random backoff
From: "Scott Miller" <scott@opentrac.org>
Date: Tue, 30 Sep 2003 14:07:06 -0700
X-Message-Number: 48
>You could say APRS' popularity in many areas has also been it's downfall,
>grin. Some math (can't remember the source or credibility to it) was that
>2m 1.2kb APRS can only handle about 50 local regular users coming across rf.
>If that's really the case, then we are pretty much long past being "screwed"
>regardless of what we do as long as we stay on one simplex 2m frequency, UI
>type protocol, and stay at 1200 baud.
I think it bears repeating that this is NOT due to the use of 1200 baud,
it's the nature of an 'Aloha' protocol. For short packets like APRS uses
(or SHOULD be using), cranking up the bit rate for shorter on-air times only
works to a certain extent, mostly because you've still got a finite delay
between the time you key up and when you can start sending data. I know
there are faster rigs out there, but for my Alinco it's about 200 msec,
whether you're sending 1 byte or 1000. I believe many of the higher data
rate protocols need longer training times before they can lock on and
exchange data - ever listen to how long it takes a 56k modem to negotiate a
connection? 1200 baud AFSK can sync up in a few transitions.
The 50 user metric is based on an average packet length plus transmit delay
time, at an average transmit rate, and the fact that a pure Aloha network
can only support about 18% duty cycle before throughput starts to drop. A
lot of airtime can be saved by properly trimming TXDs and keeping your>this 'random" hold off shoots ourselves in the foot as it can reintroduce a
>packet that just "died out" on an adjacent digi by putting the one it's been
>holding for an open channel (+ the random hold off time value) back into the
On an ALOHA channel there should be a lot of silence periods so the hold
off should never be very long, most certainly not 30 seconds. You don't
need to predict when the channel is empty, you can just send at random and
the chance of a collision will be low. This is true as long as the channel
is not overloaded, i.e. not above 18% utilisation. If in 60 seconds you
count more than 10 seconds worth of data, the channel is overloaded... It
should be silent appoximately 50 out of 60 seconds.
In a environment with so many hidden transmitters carrier detection is
useless and random transmissions can not be predicted. The only small gain
you can achieve is to prevent digis from jamming eachother...
Kind regards,
Henk.
----------------------------------------------------------------------
Subject: Re: Cheap GPS receivers / RS232 / Digitraveller
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Tue, 30 Sep 2003 17:25:23 -0400
X-Message-Number: 53
>>I'm pretty sure it does, as long as you've got the memory to hold the maps.
>>Not sure if it comes with the right cable, though.
>>-
>>
>Mine came with three cables. Non of them fit my Palm IIIxe. I was able
>to find one of each, serial and pda. One is going to be taken apart to
>use with my Tini track and old Yaesu handheld.
Radio Shack is closing out a cable that hooks to Palm III and VII
series that has a DB-9F on the end. Generic serial.
Cat # 25-946, closeout priced at $4.97
Mike
----------------------------------------------------------------------
Subject: Re: ***New*** TRACEn-N (LANn-N) Paradigm
From: "Scott Miller" <scott@opentrac.org>
Date: Tue, 30 Sep 2003 14:36:13 -0700
X-Message-Number: 54
I keep looking at my Xastir map and trying to figure out how to apply this
to the local area, but I'm just not getting it. I guess it's still the
mobiles passing through that get me. How do they get to my IGATE when they
don't know the local settings, and can't get there with WIDEn-N? Even
within the 'LAN', there are plenty of areas that would take more than one
hop to reach the IGATE, especially for a mobile.
Here's an idea that'd be easy for DIGI_NED to implement, but might be a bit
harder for embedded digis... allow the user to define a polygon, in
geographic coordinates, that bounds the LAN. Compare the position in all
packets to the LAN boundaries, and set a bit declaring it 'inside' or
'outside' and allow routing decisions based on that.
Scott
N1VG
----------------------------------------------------------------------
Read previous mail | Read next mail
| |
