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ZL3AI > APRDIG 04.05.03 19:42l 198 Lines 7224 Bytes #999 (0) @ WW
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
TAPR APRS Special Interest Group Digest for Tuesday, April 29, 2003.
1. PCSAT Nearly QRT
2. RE: PCSAT Nearly QRT
3. Re: Alinco DR-135TP
4. RE: PCSAT Nearly QRT
5. ATM adapters
6. Re: ATM adapters
7. Malaysia on APRS
8. D-700 Smart Beaconing
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Subject: PCSAT Nearly QRT
From: Bob Bruninga <bruninga@usna.edu>
Date: Tue, 29 Apr 2003 12:55:12 -0400 (EDT)
X-Message-Number: 1
PCsat is back in eclipses and its batteries are practically shot. On
saturday it went back to negative power budget and so it can now barely
even work in the sun due to the peak power needed for each packet burst.
The only packets that can possibly get through even while PCsat is in the
sun are VERY SHORT.
The best very short packets are Mic-E formatted packets or Kenwoods which
can contain a callsign, position, course and speed with only 9 bytes in
the payload. Thats about a 0.2 second data burst. Unfortunately the TXD
on PCsat defaults to 300 ms and so it is sending 0.3 seconds of overhead
to send just 0.2s of data. But that 1/2 second packet is about all you
can get through now.
Also since the UHF receivers default to ON, and they listen for 9600 baud
packets, you can really get some short packets through that way too.
Just set your D7 or D700 to 9600 baud and split band operation. Ah! You
can also transmit up on 1200 baud and use the DIGI path of VIA XBAUD and
your 1200 baud packet will come back down at 9600 baud, also making a very
short packet.
For all practical purposes except for experimenting with these short
packets, I'd say PCsat's mission for providing a continuous availability
of an AX.25 digipeater for UI packets on 145.825 is over. The next full
sun isn't till July 12th and thats another 1000 deep cycles on the
batteries.
I hope other satellite designers are considering adding such transponders
in the future to continue this "easy-sat" technology.
WB4APR@amsat.org, Bob
PCsat WEB page http://www.ew.usna.edu/~bruninga/pcsat.html
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Subject: RE: PCSAT Nearly QRT
From: Miller Scott Contr 30SCS/FTI <Scott.Miller@vandenberg.af.mil>
Date: Tue, 29 Apr 2003 17:19:23 -0000
X-Message-Number: 2
It'll be sad to see PCsat go. Hope it hangs in there for a while.
I'm curious why the long TXD was set as the default. And why the lack of
nonvolatile configuration storage? I understand the need for a failsafe
reset mode, but it seems to me you could still implement a watchdog
timer/counter that'd save you from doing something silly like setting the
command receiver to default to 'off'.
Was PCsat built with radiation hardened components, or regular off-the-shelf
stuff? Do you have any estimate of the total dose it's taken, or the number
of single event upsets it's had? If memory serves, the flux in the South
Atlantic Anomaly is pretty strong at that altitude, though it wouldn't be
there that much in a polar orbit.
You mentioned PCsat2 going on ISS... it's going to be a package attached to
the station, and not a free-flying satellite? How's it getting there?
Soyuz, Progress, or Shuttle? What's its expected lifespan?
Scott
N1VG
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Subject: Re: Alinco DR-135TP
From: "Dick C. Reichenbach" <dreichen@columbus.rr.com>
Date: Tue, 29 Apr 2003 13:41:33 -0400
X-Message-Number: 3
Digi_ned is probably a pretty stable program for this type of application,
but I still like Mike Musick's idea for PocketDigi
(http://www.pocketaprs.com/pocketdigi.html) I recently saw a new Palm M100
(no box, manual, software, or sync cable) for around $40 and would use a
lot less power than even a small old laptop.
Dick Reichenbach - KC8OBZ
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Subject: RE: PCSAT Nearly QRT
From: Bob Bruninga <bruninga@usna.edu>
Date: Tue, 29 Apr 2003 14:40:05 -0400 (EDT)
X-Message-Number: 4
On Tue, 29 Apr 2003, Miller Scott Contr 30SCS/FTI wrote:
>I'm curious why the long TXD was set as the default.
To guarantee commandability from fundamental ROM defaults.
>And why the lack of nonvolatile configuration storage?
PCsat has all defaults in non-volatile ROM to guarantee a clean start and
the ability to communicate after an anomoly. It can be re-configured in
RAM as long as it has power. When it looses all power, it goes back to
defaults.
>I understand the need for a failsafe reset mode, but it seems to me you
>could still implement a watchdog timer/counter that'd save you from
>doing something silly like setting the command receiver to default to
>'off'.
PCsat has 3 watchdog timers. Two reset the TNC's if they dont transmit at
least once a minute. THe third resets everything if it has not been
cleared at least once every 70 hours.
PCsat dafaults to backup-receivers ON, becuse a backup receiver is of no
value if it is off after an anomoly. Our ops plan was to command them
back off whever they were not needed to save power. But they must default
to ON or they are useless.
>Was PCsat built with radiation hardened components, or regular off-the-shelf
>stuff?
Normal stuff. But I did epoxy a thin 1/16th" thick 1/2" square chip of
lead over the EPROM and the CPU. Top and bottom of the chips.
>Do you have any estimate of the total dose it's taken, or the number
>of single event upsets it's had?
No. We have no resets that we can attribute to SEU's because with the
lack of one solar panel, whenever we were in eclipse seasons, we were
getting loss-of-power resets every orbit. But during periods of full
sun which occurred at least 6 periods for two weeks at a time, we never
experienced a TNC lockup due to an SEU that we could tell.
>You mentioned PCsat2 going on ISS... it's going to be a package attached to
>the station, and not a free-flying satellite? How's it getting there?
>Soyuz, Progress, or Shuttle? What's its expected lifespan?
Its going up by Shuttle as a high priority DOD mission. or Soyuz if DOD
can get on it. See the web page.
http://www.ew.usna.edu/~bruninga/pcsat2.html
de WB4APR, Bob
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[commercial content deleted]
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Subject: Malaysia on APRS
From: Bob Bruninga <bruninga@usna.edu>
Date: Tue, 29 Apr 2003 18:56:09 -0400 (EDT)
X-Message-Number: 7
I have a point of contact in Malaysia interested in APRS. If anyone knows
of anyone else, lets get them talking...
de WB4APR@amsat.org, Bob
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Subject: D-700 Smart Beaconing
From: "Darryl Smith" <Darryl@radio-active.net.au>
Date: Wed, 30 Apr 2003 13:56:43 +1000
X-Message-Number: 8
People
I seem to remember that someone has implemented a smart beaconing for
the Kenwood D700. Can anyone give me a pointer to that project?
Many thanks
Darryl
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Darryl Smith, VK2TDS POBox 169 Ingleburn NSW 2565 Australia
Mobile Number 0412 929 634 [+61 4 12 929 634 International]
Darryl@radio-active.net.au | www.radio-active.net.au
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