(an archived page, this may contain outdated or
speaker . . .|
Tim Cunningham - N8DEU .
is considered by many as the local 'Packet Guru'.
is also known as an Area Coordinator for AMSAT Field Operations.
discussion on APRS basics,
from an exchange on
the 'HARC-AL' YahooGroup email reflector - June 2008
this exchange was prompted by Tim's article in the HARC-VOX
newsletter for July 2008
"APRS - The Tactical
Communications Solution for the Emergency Network"
was asking Tim (N8DEU)
for some basic setup info
- both have graciously allowed
SomeNet to re-publish their dialog
is part < 1
> of a special series)
|----- Original Message
Cunningham" < n8deu@_x_x_x_>
To: "Travis" <
Cc: < email@example.com
Sent: Monday, June 23, 2008 10:56 AM
Re: APRS basics
I read your
passionate article in the VOX about APRS for emergency nets.
You could say I am a little a
passionate about my hobby.
Anything worth doing is worth
doing it well.
> Could you say what minimum
and recommended equipment is needed to transmit APRS text for
each of two situations: Fixed
station with Internet access; and a mobile station.
beauty of the APRS tactical communication system is the lower cost
entry point in comparison to some of the other digital modes. They all
have their unique usefulness in different ways.
For a fixed station the
following equipment scenario's could be utilized for messaging.
1. Radio, computer, and use
the sound card with AGWP software as the TNC.
Radio, computer, and TNC. A TNC could be a standard 1200 baud
AX.25 Kantronics, MFJ, Pac-Comm, Symtek or it could be a TNC-X
(KISS only TNC).
Computer with Internet access (no radio or antenna required).
APRS works seamlessly between the RF world and the Internet. I
once had a keyboard QSO with a German HAM via my 2 meter APRS
mobile driving through the hills of WV and found that he had
tracking my travels the entire day.
Kenwood TMD-700A or TMD-710A mobile. Kendwood TH-D7A handheld.
They have a built-in 1200/9600 baud TNC and an interface on
display where you can send messages back and forth without a
computer by using the buttons on the microphone to compose
messages. I just had a QSO with a HAM in Decatur from my
this morning driving down I-65. The Alinco DR-135T has a
1200 baud TNC to support APRS as a tracker but it does require
computer for messaging or you could use a Palm Pilot or
any Windows CE or Windows Mobile handheld device. They all
the ability to act as digipeaters to help move traffic from
location to another if line of site is an issue or a
goes down (no proprietary software required). Every station on
network can be utilized as a digipeater if needed. This adds
redundancy to the network. My cell phone by itself works great
a handheld application since it also has a buit-in GPS and
eliminates the need for a laptop.
A mobile station with
messaging capability can consist of the following configurations:
Radio, TNC, and a laptop computer or Palm Pilot or Windows CE
or Windows Mobile handheld device. A GPS is optional unless
want/need to provide real time location information. Some
opt to forego the GPS and manually indicate their position by
clicking it on a map. Objects can be placed on a map by any
to alert others of pertinent activity or issue at that
(power lines down, traffic blocked, tornado damage, etc). NWS
mesages are also received by all stations in a
simultaneous broadcast protocol in the event of severe
APRS users always know what is happening with the weather
2. Radio, laptop, and use the
sound card with AGWP software as the TNC.
Kenwood TMD-700A or TMD-710A. It has a buit-in 1200/9600 baud TNC
and an interface on the display where you can send messages
and forth without a computer by using the buttons on the
microphone to compose messages. One of the Alinco Radio's have
built-in 1200 baud TNC to support APRS as a tracker but it
require a computer for messaging or you could use a Palm Pilot
any Windows CE or Windows Mobile handheld device. My cell
works great in this application since it also has a buit-in
and eliminates the need for a laptop or a desktop as
that function. Heck, my phone eliminates the need for a
radio since it has internet access, APRS software, and a
4. There are numerous other
configurations with tracker only capability, etc...
For those 2
categories, what software and firmware is needed, and what operating
systems are supported?
most operating systems are supported like Linux, DOS,
Windows, MacIntosh, Palm Pilot, Window Mobile, Windows CE,
The Kenwood radios can be used as a standalone system since
have a user interface. Although, you could connect a computer
the Kenwood radio and use it as well.
software is generally required on a computer along with a
map application (Delorme Street Atlas v9.0 or lower and not
Deluxe version, Precision Mapping, Microsoft Mapping, and many
support screen capturing of a map to utilize. The screen
method provides the ability for everybody to view the same map
display, but it does not allow you to zoom into street level
detail like the software map programs.
equipment and software would be needed by a net control station
to see the weather bulletins, the map plot, and a list of all
check-ins--and respond by radio?
2M Radio, computer, and a TNC unless you use a radio with a built-in
TNC or use the sound card as the TNC. You would also need one
the many APRS software packages. Some are free and some
registration fee. The final piece would be the mapping
which can be Delorme Street Atlas verion 9 or below, Precision
Mapping software, Microsoft Maps, or captured maps from a
shot. The weather bulletins are transmitted in real time from
local I-Gate immediately. You could get by without a radio if
had an Internet connection. In real disaster, we would rely on
radio network link and battery back-up power.
How would an
APRS-centric weather net operate?
much different than the voice net. A message can be broadcast to
all users opening the net and inviting check-ins by indicating
what they should provide in their response. When the message
received by the net control the users software will get an
acknowlegment message that their message was received so their
transmiter will not repeat the traffic and free up the data
channel. The net control can have an automatic message
the sender immediately upon receipt with an automatic message to
their inbox or the net control can chose to manually
with individual messages or a broadcast to all stations with a
list of those stations that are being acknowledged (the best
approach to reduce data congestion).
is the max. size of any one text or weather message, not counting the
usual position information? (Would stations give detailed reports via
really no maximum size of a message with the exception of
data is sent in a single packet. A paragraph of text can be sent
at one time, although it will be broken down into multiple
transmission of data as to prevent hogging the bandwidth of
data channel. APRS is designed to process the most current
information as quickly as possible. The Kenwood data radios
limit a line of text to 40-60 characters on a single line.
the software packages also limit data to 60 characters per
but they are simply sent in an additional transmission as a
separate message and in the logical order so it can be read as
intended. Bulletins broadcast to all stations are very easy
to ready when multiple lines of text are transmitted.
basic and elementary answer (or column) from you would be appreciated,
though I imagine you also know some Web sites to refer us to.
Here is some good information
Also you might want
to reply on firstname.lastname@example.org to get 30 or 40 readers.
Travis Hardin, KE3Y
Have a Great Day!
organizations are consolidating some of the overhead associated with
registration and training of the membership. Join us on the 2nd
Thursday evening of each month for a good meeting at the HMC EMA EOC
(and learn more about this).
Remember, the severe weather
season is available year-round.
|Additional discoveries, rants and
and experiments :|
+ Be sure to check www.somenet.net
for interesting articles inbetween updates to this page.
= Narrow Band Emergency Messaging System - check it out (new Yahoo
Propagation Map = using APRS beacons to visualize current
+ APRS.FI = another view of
the APRS-IS database, from Finland.
= My weather instruments are still active and logging.
I'm not yet satisfied with the radiation shield I made for the external
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2005 . . .
organizations, projects and web sites
that I continue to support and