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ZL3AI > APRDIG 14.12.03 10:42l 162 Lines 5985 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Dec 11, 2/2
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: APRS-IS messaging?
From: Bob Bruninga <bruninga@usna.edu>
Date: Thu, 11 Dec 2003 18:21:43 -0500 (EST)
X-Message-Number: 17
Long-Haul APRS messaging via RF==>APRSis==>RF barely works.
As a data point, I sent a short one line messsage to about 65 stations
randomly chosen all over the country. Here are the statistics showing the
number of hops on the far RF link:
22 Successes
14 were direct to their IGate
5 were 1 hop away
2 were 2 hops
1 was 3 hops
34 Failures (Of these, the following is their distance from their IGate)
5 were direct
12 were one hop
9 were two hops
2 were three hops
6 were not heard in the last 10 hours or more
My local path on RF was VIA WIDE and was hitting the IGate for our area as
confirmed on FINDU. All of the above statistics were also gleaned form
FINDU to see the path on each station at the other end. The test began
around noon Eastern Time on a thursday so the QRM was "nominal" (Not rush
hour)...but ended at 6 PM..
To keep channel load low, I only had about a dozen outstanding outgoing
messages at a time and only added a new one when one finally got delivered
or I gave up. The test lasted 6 hours.
Remember, for just a 1 hop on both ends that still requires 4 RF links
going outbound and a total of 8 total hop probabilities to get the ACK
back. So again, do NOT expect MESSAGES that require ACKS to perform
well in APRS flooded nets via the APRS-IS with hops on both ends...
de WB4APR, Bob
----------------------------------------------------------------------
Subject: RE: APRS-IS messaging?
From: "AE5PL Lists" <HamLists@ametx.com>
Date: Thu, 11 Dec 2003 17:29:55 -0600
X-Message-Number: 18
Also remember, there are some one-way IGates out there (gating to
APRS-IS but not to RF). Keep in mind, too, that just because an IGate
hears a station 1 hop away, the IGate may take 2 or more hops to get to
that station as the IGate may have better ears (and less interference)
than the 1 hop digi.
In the DFW area, messaging 2 or more hops away on RF only barely works
so I am not surprised by your results.
73,
Pete Loveall AE5PL
pete@ae5pl.net
----------------------------------------------------------------------
Subject: Using PSK31
From: cdapples <cdapples@cablemt.net>
Date: Thu, 11 Dec 2003 18:48:49 -0700
X-Message-Number: 19
Is there any thought about using PSK31 for APRS on HF and/or VHF?
--
Chris / KF7KN
+===============================+================================+
| Charles C. Dapples, Ph.D. | Red Lodge, Montana, USA |
+-------------------------------+--------------------------------+
| e-mail: cdapples@cablemt.net | Telephone: (406) 698-4989 |
+ or +--------------------------------+
| kf7kn@amsat.org | |
+-------------------------------+--------------------------------+
| Web page: http://www.rlsart.net |
+===============================+================================+
----------------------------------------------------------------------
Subject: Re: Using PSK31
From: Richard Garcia <k4gps@bellsouth.net>
Date: 11 Dec 2003 21:14:22 -0500
X-Message-Number: 20
Was a long time ago... Support for the application went away from the
author but the program may still be floating about somewhere.
Rich
----------------------------------------------------------------------
Subject: Re: Using PSK31
From: "Stephen H. Smith" <WA8LMF2@aol.com>
Date: Thu, 11 Dec 2003 20:53:22 -0800
X-Message-Number: 21
cdapples wrote on 12/11/2003, 5:48 PM:
>Is there any thought about using PSK31 for APRS on HF and/or VHF?
This has been dicussed many times.
The problems are:
1) PSK31 is 10 times slower than even 300 baud HF packet (40 times
slower than the usual VHF packet); even a simple posit takes 10-15
seconds to send. This means the channel capacity (number of stations
that can be supported) is extremely limited
2) There is no error detection or correction to ensure valid data at
the receiving end. With normal AX25 packet, even an unconnected packet
(as used in APRS) goes through an error detection process at the
receiving end. It will not be passed out of the TNC (hardware or
software) to an application if it is somehow defective. [ Unless you
have the passall "junk" mode turned on in a TNC.]
3) The tuning accuracy requirements for PSK31 are so precise that
trying to transmit beacons "in the blind" to a receiver that doesn't
transmit back would require 10 or even 1 Hz display resolution and an
extremely-accurately-calibrated, high-stability TCXO in the user's radio.
All that being said, there is a group of people that are doing this. An
activity similar to APRS, BeaconNet, transmits PSK31 APRS-format data on
10 meters. The purpose of BeaconNet is to monitor propagation, not
track the positions of mobiles. As a result, nearly all the the
transmissions are made by a handful of fixed stations and most of the
users just listen.
They are using an application written by G4IDE (the author of UI-View)
called PSK31 Server. This is a waterfall-display-type PSK31 program
that looks very similar to DigiPan but has the added twist of a built-in
TCP/IP server and interface. You configure the Internet connection of
any standard APRS program to connect to your own IP instead of one "out
there" on the Internet. [ Most of the users are using UI-View. ]
G4IDE is no longer supporting the program -- it was really just an
experimental quick hack -- but it is available in the archives of the
Yahoo group " ui-view_PSK31 " and from the BeaconNet website at:
http://go.to/beaconet
Stephen H. Smith wa8lmf (at) aol.com
Home Page: http://wa8lmf.com
Ham Radio/Mobile SSTV page: http://members.aol.com/wa8lmf/ham
APRS Stuff
http://members.aol.com/wa8lmf/aprs
---
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