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PA2AGA > TCPDIG 29.12.97 20:37l 145 Lines 5857 Bytes #-10119 (0) @ EU
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From: pa2aga
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Subject: TCP-Group Digest 97/97C
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I have much more learning to do on these topics, some day I intend to have
mastered them all :)
________________________________________________________________________
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darxus@op.net / http://www.op.net/~darxus
Become a part of the network: http://www.distributed.net
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Date: Mon, 29 Dec 1997 09:11:15 +0000 (GMT)
From: Alan Cox <alan@cymru.net>
Subject: TCP/IP over AX.25 on a wearable ?
> now I ask my question and snow how little I know about packet radio: can
> the equipment necessary to do AX.25 be built into a wearable computer --
> is it small enough, and does it require little enough power to run off of
> batteries ?
We played with this a bit using the PC110 (IBM's 486SLC smaller than a
paperback book). The longer range license exempt radios on 458MHz in the UK
put out about .5W and that seemed to challenge nicads a little to well.
Possibly with gel cells and similar things it might work. The low power
stuff is < 100mW but doesn't tend to go very far, and the microwave stuff
is extremely line of site.
People have operated and do operate AX.25 packet radio mobile with
"designed for the job" handheld 2m FM radio equipment.
Alan
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Date: Sun, 28 Dec 1997 23:53:50 -0500
From: Steve Mann <mann@eecg.toronto.edu>
Subject: Wireless WearComp
Since I didn't see anyone answer your question, I will attempt
to formulate an answer (to your question from some time ago).
>one of the problems with wearable computing seems to be networking.
>options being wireless modems (expensive air time), or wireless lan type
>stuff (short range).
>AX.25 is a wonderful thing I ran across a while ago on the web -- a
>protocol that runs over packet radio (hams). TCP/IP can be (and is)
>encapsulated in AX.25, and gatewayed to the Internet. the whole TCP/IP
>over AX.25 seemed like it would be most cool if everybody had a tranciever
>-- broadcasting & recieving their own signals, and relaying other people's
>signals to distant sites.
I've been experimenting with this for a number of years, and found it
to be the best way to go, not only cheaper than cellular, but much
more reliable.
You might want to take a look at the feature article of Jan.'97 CQ-VHF
which describes wireless WearComp in more detail.
Let me know if you can't find that issue, and I'll put the text online
or maybe include the info in wearhow
(http://genesis.eecg.toronto.edu/wearhow/index.html)
>now I ask my question and snow how little I know about packet radio: can
>the equipment necessary to do AX.25 be built into a wearable computer --
>is it small enough, and does it require little enough power to run off of
>batteries ?
A small battery-powered rig is preferable. I recommend the Kantronics
TNC if you're planning on running TCP/IP over the radio, as that's a good
place for a beginner to start. If you're more adventurous, or get tired
of this, you might want to build a WA4DSY system (above is a G3RUH).
The former has the advantage that it will work at 19k2 or lower rates
such as 1200bps. Thus you might use it with a standard HT at 1200bps
for a while, and then upgrade to 19k2 by hacking a Micor or Tekk, opening
up the front end a little.
I find 440MHz works well for WearComp use, since it's a good compromise
between penetrating capability and reflectivity in urban and indoor
environments, and doesn't heat up the brain as much as microwave
frequencies (e.g. cellular, or amateur packet in the 33cm or 23cm band).
I've maintained two gateways, one at 19k2 and the other at 56k, both
in that band, for wearcomp connectivity. You may want to also set up
your own gateway to maximize throughput.
If you're using the standard WearComp6 design
http://n1nlf-1.eecg.toronto.edu/wearhow/index.html
you can put the radio right inside the same box, and heatsink it to
the case. That gives you a 1 box solution. Also WearComp6 runs off 12
volts, and so does the Kantronics TNC and both the above radios.
Tekk works best at 10volts Rx and 12-13volts Tx, so you might split it
up and regulate the Rx while running the Tx "dirty" (right off the
battery). However, I found that a DATEL 12 to 12 volt isolating
regulator worked with the Tekk+Kantronics combo with no noticable
loss in performance over a Ni-Cad (e.g. well-regulated cell).
That allows you to use Li-Ion and cut the weight. Quite a few fellow
hams told me it would never work well with an ISR, but I proved them
all wrong by getting very reliable communication with lightweight
Li-Ion batteries SONY donated to me some years ago (back then you
couldn't buy the Li-Ion camcorder batteries, so perhaps folks hadn't
had much chance to try them then). Now you can get them at any good
consumer electronics distributor, so that's probably the best way to go.
I hope I've answered your question about battery draw; if anyone else
has had experience with battery-powered TCP/IP, please feel free to
add to this.
73 de N1NLF
Professor Steve Mann
University of Toronto,
Department of Electrical Engineering, Room S.F. 2001,
10 King's College Road; Toronto, Ontario, Canada; M5S 3G4
Tel. 416.946-3387 Fax. 416.971-2326
http://www.eecg.toronto.edu/~mann
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End of TCP-Group Digest V97 #97
******************************
Both my XYL and myself wish you a very
happy and prosperous New Year. Adam PA2AGA.
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