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ZL3AI > APRDIG 17.09.03 11:18l 227 Lines 9437 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Sep 14, 2/2
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: AX.25 / HDLC question
From: "Scott Miller" <scott@home.miller.org>
Date: Sun, 14 Sep 2003 12:39:47 -0700
X-Message-Number: 11
I'm working on debugging my tinytrak-style tracker... I've got a 2211 FSK
decoder set up for testing, and I'm able to capture its output on a scope
and it's exactly what I'm expecting to see. I can decode it by hand and see
that all of the HDLC flag sequences and bit stuffing look fine. Nothing
else decodes it, though. So for comparison I had my KPC-3 transmit the same
packet and captured it.
The output doesn't look similar at all, so I'm guessing it's my
understanding of HDLC that's flawed. To start with, I expect a preamble of
flags - the flag sequence is 01111110, so it should start with a bunch of
011111100111111001111110. What I see looks like 01111111 repeating, which
is the HDLC abort sequence. Now I suppose there's no reason you couldn't
fill airtime with aborts, though I think it's supposed to be either 1's or
flags if it's idle, but I don't see anything that looks like a valid flag
sequence at the start of the frame. Which makes it that much harder to
figure out how the data's different when I can't figure out exactly where
the frame starts.
Is there anyone out there who's messed with packet at this level and might
know where I'm going wrong?
Thanks...
Scott
N1VG
----------------------------------------------------------------------
Subject: Re: aprssig digest: September 13, 2003
From: Tom Weeden <wj9h@arrl.net>
Date: Sun, 14 Sep 2003 14:42:22 -0500
X-Message-Number: 12
At 12:00 AM 9/14/03, hasan, N0AN wrote:
>Is there a SIMPLE way to put this emergency battery supply in parallel with
>the existing Astron, such that when AC mains are lost, it will
>instantaneously switch to the backup battery that is being float charged.
>(This is one of those automobile strarting portable battery setup with cig
>light plug, light, etc)
>
>I need to have it switch automatically, and be properly isolated from the
>Astron when power is on or comes back on. I seem to remember there is a
>trick with a diode that will allow this. Could someone please clue me in,
>and be specific!
>
>TIA,
>
>..hasan, N0AN
Yes! April 1990 QST, page 33, had an article on modifying the Astron
supply so you could parallel it with a battery. You have to add a 6.8-10k
resistor between pin 4 of the 723 regulator IC and the wiper of the voltage
adjustment potentiometer. I used an 8.2k resistor, and have been running
in parallel with a deep-cycle battery with no problems for several years.
--Tom Weeden
Amateur Radio WJ9H
Madison, Wisconsin
www.qsl.net/wj9h
----------------------------------------------------------------------
Subject: RE: AX.25 / HDLC question
From: "Scott Miller" <scott@home.miller.org>
Date: Sun, 14 Sep 2003 13:21:13 -0700
X-Message-Number: 13
Ok, I think I've got it figured out. I could have sworn packet used NRZ
encoding, but now I see some references to NRZI. Why is there so little
documentation on the physical layer?
----------------------------------------------------------------------
Subject: RE: AX.25 / HDLC question
From: John Hansen <hansen@fredonia.edu>
Date: Sun, 14 Sep 2003 17:48:11 -0400
X-Message-Number: 14
Correct, it's NRZI. In addition, you can't count on the transmitting
stations idling with flags. Many TNC's idle with 0's instead, sending just
one flag before the packet. For probably more details on all of this than
you ever wanted see the following:
1. Hansen, John, PIC-et Radio: "How to Transmit AX.25 UI Frames Using
Inexpensive PIC Microcontrollers" in 17th ARRL and TAPR Digital
Communications Conference Proceedings (Newington, CT: American Radio Relay
League, 1998) pp. 29-37.
2. Hansen, John, PIC-et Radio II: "How to Receive AX.25 UI Frames Using
Inexpensive PIC Microcontrollers" in 19th ARRL and TAPR Digital
Communications Conference Proceedings (Newington, CT: American Radio Relay
League, 2000) pp. 67-74.
3. Hansen, John, "TNC-X: An Expandable Microcontroller-Based Terminal Node
Controller" 2003 Digital Communications conference, forthcoming.
The first two papers can be found on: ftp.tapr.org under the
directory: pub/wa0ptv The files are DCC.ZIP and DCC2.ZIP
The final paper can be found at a link on the bottom of the page
on: http://www.tnc-x.com
Good luck with your project.
----------------------------------------------------------------------
Subject: Hurricane Isabel
From: dale huguley <kg5qd@wxsvr.net>
Date: Sun, 14 Sep 2003 23:03:08 +0000
X-Message-Number: 15
Hi All-
This is being written on Sunday Sept. 14th at 6 pm EDT. Hurricane
Isabel is predicted at 1800 Z Sept 18th (Thursday) to be on the Border
of North Carolina and Virginia at the coast. Winds are predicted to be
105 knots (120 mph) gusting to 150 mph. I will go over some
fundamentals about the way hurricanes are presented by Wxsvr.
The "+12h" "+24h" "+36h" etc. predicted positions are relative to the
synoptic time of the forecast , not the not necessarily the actual time
of the forecast. This can cause the times to be 3 to 6 hours
earlier than one would think. There is always an information packet
sent with the synoptic time.
Wind radii available from the Hurricane center are:
Present(ato), +12h , +24h, + 36h have Hurricane force (65 knot - 74
mph) , Whole Gale (50 knot - 57 mph) ,and Tropical Storm force (35 knot
- 39 mph)
+48h and + 72h do not have Hurricane force radii
+96h and +120 do not have any radii available
Present and Future positions are updated at 0300z 0900z 1500z and 2100z
- or as much as 45 minutes before these times. There is a possibility
that the previous set could get retransmitted after a new set is sent in
the time before they expire. The time stamp (just after the object
name) is the expiration time not the issue time if there is any
confusion. As a major Hurricane threatens- the Present position will be
updated every 3 hours , then every 2 hours, and possibly every hour as
the threat increases. The updated position carries the name plus
"_upd", but may or may not have any wind radii or pressure info.
The positions are generally a blend of the computer models, plus some
seat-of-the-pants finagling by the Hurricane Center.
A great place to look at the models in action is at:
http://met.psu.edu/tropical/tcgengifs/
The gfdl has been preforming very well during Isabel (also the coolest
graphics) . click "submit" on the sealevel pressure or rainfall- and
wait for the 20 or so frames to load - Then "FWD"
User definable sat loops are available at:
http://wwwghcc.msfc.nasa.gov/GOES/
for Isabel use the "Caribbean and West Atlantic Region from GOES East"
pick "animation" and the size of the zoom then click near Isabel
Remember before and during a hurricane landfall, your WX and damage
reports are vital to the Hurricane Center. If you are unsure of the
I-gate/internet/aprs-is situation due to storm conditions, please relay
them via the Hurricane watch net
http://www.hwn.org/
Or via IRLP,e-mail, fax, or message-in -a-bottle to the folks at WX4NHC
(ex W4EHW) located at the Hurricane center
http://wx4nhc.com
or have someone close enough to communicate with you or your group- but
out of the affected area - relay them for you.
Do not put yourself in harms way to relay wx info.
At the time of this writing- Isabel is predicted to affect a large
portion of the population of the US. The "wet side" or Northeast
quadrant will have everyone from Virgina to New England in for lots of
rain- even ignoring the 150 mph gusts at landfall.
73 and good luck de kg5qd Dale
----------------------------------------------------------------------
Subject: Re: [amsat-bb] PCsat special event Sun Eve
From: Bob Bruninga <bruninga@usna.edu>
Date: Sun, 14 Sep 2003 21:39:10 -0400 (EDT)
X-Message-Number: 16
SUnday night PCsat test:
I see 50 stations now on http://pcsat.aprs.org in the last 27 hours, so
activity is picking up. You will notice that we overloaded her at about
0042z and she RESET, but so far the side B commands are holding her in
OPS NORMAL. As long as you see the telemetry showing 00111111 then the
UHF receivers are off and she is saving power.
You can tell though that only side B is holding this because side B is
ending with 01XX,1 and side A is only showing 00XX,1. That second bit is
the one that saves 50% of PCsat power by isolating the transmitters. If
both of those telemetry show 00XX,1, then the transmiters are
crossconnected and every packet on either 145.825 OR on 144.39 is using
BOTH transmitters. And our weak batteries cannot produce that peak
current.
My next chance to command the A side is at 0800 EDT on Monday.
>PCsat digipeats via RELAY, WIDE, W3ADO-1, APRSAT and PCSAT-1 if it stays
>configured as we like.. Thus, it should operate like any APRS digi
Also, until we re-load the A side, then the only digi call that is woring
is W3ADO-1...
de WB4APR@amsat.org, Bob
PCsat WEB page http://www.ew.usna.edu/~bruninga/pcsat.html
ISS-APRS FAQ: http://www.ew.usna.edu/~bruninga/iss-faq.html
CUBESAT Designs http://www.ew.usna.edu/~bruninga/cubesat.html
APRS LIVE pages http://www.ew.usna.edu/~bruninga/aprs.html
APRS SATELLITES http://www.ew.usna.edu/~bruninga/astars.html
MIM/Mic-E/Mic-Lite http://ssdl.stanford.edu/mims/
---
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