APRS is a registered trademark Bob Bruninga, WB4APR Copyright © 2004 – John Beadles, N5OOM All Rights Reserved Hamcom 2005 Configuring APRS Digipeaters.

APRS is a registered trademark Bob Bruninga, WB4APR

Copyright © 2004 – John Beadles, N5OOM

All Rights Reserved

Hamcom 2005

Configuring APRS Digipeaters in 2005Rev 1

Presented by

Ken Isom

[email protected]

Most slides from “Intro to APRS Digipeaters” by Rich Casey, N5CSU and “Intro to APRS” by John Beadles, N5OOM



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Hamcom 2005

Goals

• APRS brief overview

• APRS configurations

• APRS improvements and latest guidelines

• APRS hardware example

• APRS KPC3 TNC specifics

• APRS DFW APRS Questions from the Floor

• APRS Resources and Final Suggestions



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Hamcom 2005

What is APRS?• APRS, or Amateur Position Reporting System, developed by Bob Bruninga, WB4APR is a system that allows users to transmit location and other data in single data packets. Usually stations being tracked use GPS receivers to provide real time tracking data.

• APRS uses existing packet TNCs (terminal node controllers) and small, low cost microcontroller driven units to transmit standard AX.25 packets on a ground frequency (in the U.S.) of 144.39 at 1200 baud. APRS can also be used over HF and satellite links.

Let’s listen…



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Hamcom 2005

APRS Applications

• Public Service Events

– Bike rallies

– Parades

– Crime prevention patrols

• Other

– Weather Stations

– Repeater advertising

– Event talk-in

• Skywarn Nets

– Spotter assignment

– Storm tracking

• Post Disaster Management

– Damage assessment

– Liaison tracking

– Logistics management

– Staging site talk in

• Search & Rescue



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Hamcom 2005

How APRS Works

• An APRS station broadcasts a packet of information, typically a GPS coordinate and other information.

• The packet is received and decoded by stations in range.

• Digipeater stations hear the packet and rebroadcast it based on

– rules in the digipeater software and

– commands that you put in the packet.



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Hamcom 2005

Problems with APRS

• APRS on VHF is a single 1200 baud shared channel.

• APRS packets take a finite amount of time to transmit; therefore, only a limited number of users may operate in a given area.

• The number of digipeaters that retransmit a packet is dependent on how each user configures his TNC.

• Misconfiguring a TNC can flood the channel. Smart digipeating can help. More on this later.

Let’s listen again…



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Hamcom 2005

PublicInternet

DigipeaterB

DigipeaterA Digipeater

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APRS-IS Server

Example (1) – Mobile Station Beacons

Step 1. An APRS station beacons and is heard by every other APRS station in direct range



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Hamcom 2005

PublicInternet

DigipeaterB


C

APRS-IS Server

Example (2) – Local Digipeater relays

Step 2. The packet is rebroadcast by the local digipeater; this packet is heard by everyone in direct range of that digipeater. It is also received by other area digipeaters.



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PublicInternet

DigipeaterB


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APRS-IS Server

Example (3) – Area digipeaters relay

Step 3. The packet is then rebroadcast by the other area digipeaters. The packet is heard by every APRS station in direct range of this second set of digipeaters, including the original digipeater.

I-GATE



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Hamcom 2005

Good, Bad & Ugly• The Good News:

– Almost anyone can be a digipeater!

• The Bad News:

– Almost anyone can be a digipeater!

• The Ugly News:

– Lots of Digipeaters out there with problems

• Distorted levels, Hum/Noise, Can’t Hearwell, Can’t Transmit very far, not adding Value



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Why do you want a digipeater ?• In the olden days Amateur Radio wanted EVERYONE to have a digipeater

to fill in. “I have this old TNC and want to get some use out of it “

• Now it is prudent to ask if one is actually needed at your location and the reasons or if another approach might be better.

• Your new Digi might help or it could hurt the existing network by overloading

• Many Digi’s are LID’s and only pollute the airwaves and cause lost packets and do not add value to the system.

• Regional or Mobile Digipeaters for specific functions or events may be the answer.Want to start a great discussion? Should Certain Events operate on 144.390 ?

• Do you have a 5 watt APRS and you want to cover 100 miles?Well, that may or may not work as well as you think. You might can hear some of the signals out there but you probably wont hearmost of them and that results in lost packets when you get stepped on. Big Problem.

Remember two other Amateur’s rules:

“We must share the limited airwaves”

“ Why spend my money on something if I don’t work or isn’t needed?”

Hear any Doubles ?



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Before Deploying APRS

• Listen, Listen, Listen Monitoring doesn’t hurt anyone….. and its cheaper too. Speaker plug to TNC or PC and you’ll get the feel.

• Discuss local needs and guidelines with existing APRS groups to ensure interoperability.

• Decide what your going to do with your APRS tool.

• Your hardware might serve better if it is installed somewhere else.. Grandma’s house, local business building, water tower etc. Again, check with local groups who know the holes in the system.

• Be a teamplayer and keep your unit in tip-top shape.



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Hamcom 2005

Digipeaters: two flavors

• Relay (deprecated – now WIDE1-1)

– A default alias that all stations share.We’re all relays but this is unnecessary in urban areas with good wides!

• Wide (deprecated – now WIDEn-n)

– Exceptional stations… coordinated with area hams to provide specific wide area coverage



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Hamcom 2005

PublicInternet

Digipeater

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DigipeaterRural

APRS-IS Server

Example (4) – Outside Area - Rural digipeaters may have different goals

ISSUE:

In Rural areas or along long stretches of highway, low-power and mobile units don’t make it back to Urban areas or into I-GATEs. Intersection of I-45 and Texas Hwy 287. May only receive within 5 miles but transmits 25 miles mostly in one direction.

Use Yagi to hit W5DCR downtown Dallas.

I-GATE

30 milesEnnis Tx

Low traffic High traffic



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Hamcom 2005

Cheap ( A Ham’s watchword) • Old MFJ TNC $20

• Old Wilson/Regency 20w VHF Radio $30

• Old Astron 12v PS $25

• Homemade Antenna $ 5

• UIDigi ROM $10

• Used Existing Tower $ 0

• Coax and cables $10

– TOTAL $100

Bad

Bad

Bad



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Hamcom 2005

Every Digi Site has different Goals

• Not very high

• 3 Element Yagi !?!?!

• Back up for Skywarn

• ROM based

4.0 miles southwest of Ennis, TX --- Report received 1 minutes 36 seconds agoStatus: Ennis, TX Ellis Co UIDIGI 1.8b6 Raw packet: KD5AIA-7>APZ186,W5DCR-3*,WIDE,qAO,N5API-4:!3216.32N/09638.33W #PHG4100/WRT-WIDEn TX Ennis, TX [email protected]



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Environmental Considerations

Winter/Summer Ferris Dump.. Dallas Trashgetting taller every day

ManMade Obstacles

“ I could always hit the 88 Machine from here “



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More about WIDES!

• Wide area digipeaters need to be coordinated with the user community

• As your network grows, a wide may need to become a relay if it will improve the network.

– A good relay is hard to find! Moving from wide to relay shows the network is getting better!

• Example: The Dallas County experience



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Avoiding the ping-pong

• With a via address of WIDE1-1,WIDE2-1, your signal will be repeated twice

– First relay (or wide) that hears you

– First wide that then hears you repeats you

• But what if someone uses wide-wide-wide?

– In the old days, you could ping, pong back and forth between digis



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Digipeaters: A Smarter Way

• Based on discussion on the TAPR APRSSIG mailing list

• Works best the more stations that do it

• Callsign substitution on retransmission

– Digipeater replaces the WIDE1-1 with its callsign

– Available in most TNCs

– Eliminates dupes

• Widen-n the next step

– Shorter user packets and smarter digipeaters



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Hamcom 2005

Decoding Widen-n

• Widen-n

– First N= total number to digipeat

– Second N + number left to go

• Example:

– N5csu-7>APT310,relay,wide2-2: retransmit via one relay and 2 wides

– N5csu-7>APT310,W5DCR,wide2-1in transit.. one wide down and looking for another!



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Hamcom 2005

How does Widen-n work?

• A widen-n digi simply repeats any packet with the via address of widen-n; but ONLY ONCE.

• It keeps a copy (or checksum) of the last 30 seconds of packets, and compares each new packet that it hears with these last ones to avoid dupes.

• This eliminates the multiple looping of packets caused by multiple generic paths such as WIDE,WIDE,WIDE when call sign substituting digis are not used (as many as 21 copies!) In a widen-n network, however, there would only be three packets.

– From digis.txt file in the APRS DOS SW by WB4APR



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Hamcom 2005

Options for Wide Area Digis

• KPC-3 or KPC-3+

• PacComm ROM in any TAPR-2 clone tnc

• DIGI_NED software on any clone PC

• UIDIGI ROM in a TAPR-2 tnc (example shown)



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Hamcom 2005

Wide Area Digipeater Settings

• Set aliases to digipeat on WIDE1-1, WIDE2-1, WIDE2-2

• Use TNC that provides callsign substitution and provides widen-n function

• Set your POSIT power-height-gain correctly

• Watch your network for possible changes

• KPC users: turn ID to off (not needed and disrupts first digi identifier) ref: http://www.ew.usna.edu/~bruninga/aprs/id-noid.txt



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Hamcom 2005

2005 TNC Settings for KPC-3 (page 1)

• 8BITCONV ON

• AUTOLF ON

• AX25L2V2 ON

• AXDELAY 0

• AXHANG 0

• BEACON EVERY 0

• BKONDEL ON

• BLT 1 EVERY 00:09:30

• BLT 2 EVERY 00:00:00

• BLT 3 EVERY 00:00:00

• BLT 4 EVERY 00:00:00

• BREAK OFF

• BTEXT

• BUDLIST OFF NONE

• CANLINE $18

• CANPAC $19

• CD SOFTWARE

• CHECK 0

• CMDTIME 1

• CMSG DISC



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• COMMAND $03

• CONLIST OFF NONE

• CONMODE CONVERS

• CONOK OFF

• CONPERM OFF

• CPACTIME OFF

• CR ON

• CRSUP OFF

• CSTAMP OFF

• CTEXT No operator here; routing to PBBS...

• CTRL A OFF

• CTRL B OFF

• CWID EVERY 0

• CWIDTEXT DE W5MRC

• DAYSTR mm/dd/yy hh:mm:ss

• DAMA OFF

• DAMACHCK 18

• DBLDISC OFF

• DELETE $08

• DIGIPEAT UIONLY



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Hamcom 2005


• DWAIT 0

• ECHO ON

• ESCAPE OFF

• FLOW OFF

• FILTER OFF

• FRACK 4

• FULLDUP OFF

• GPSINIT

• GPSHEAD 1

• GPSHEAD 2

• GPSHEAD 3

• GPSHEAD 4

• GPSPORT 0 NORMAL CHECKSUM

• HBAUD 1200

• HEADERLN OFF

• HID OFF

• HTEXT

• INTFACE TERMINAL

• LEDS ON

• LCOK ON



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• LFADD ON

• LFSUP OFF

• LLIST OFF NONE

• LT 1 !3317.02NN09634.37W#PHG5530 Collin Cty Wide Digi /A=000680




• LTP 1 APN390

• LTP 2 APN390

• LTP 3 APN390

• LTP 4 APN390

• LTRACK 0

• MONITOR OFF

• MALL OFF

• MAXFRAME 4

• MAXUSERS 1

• MBEACON OFF

• MCON OFF

• MCOM OFF

• MHEADER OFF



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Hamcom 2005


• MRESP OFF

• MRPT OFF

• MSTAMP OFF

• MXMIT OFF

• MYCALL W5MRC-15

• MYALIAS

• MYDROP 0

• MYNODE W5MRC-15

• MYPBBS NOPBBS

• MYREMOTE W5MRC-10

• NDWILD OFF

• NEWMODE OFF

• NOMODE OFF

• NTEXT

• NUMNODES 0

• PACLEN 0

• PACTIME AFTER 10

• PASS $16

• PASSALL OFF

• PBBS 0



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Hamcom 2005


• PBFORWRD NONE EVERY 0

• PBHEADER ON

• PBHOLD ON

• PBKILLFW OFF

• PBLIST OFF NONE

• PBLO NEW VARIABLE

• PBPERSON OFF

• PBREVERS OFF

• PERSIST 0

• PID OFF

• PMODE CMD

• PTEXT

• REDISPLA $12

• RELINK OFF

• RETRY 10

• RING ON

• RNRTIME 0

• RTEXT Your Password Here

• SCREENL 0

• SENDPAC $0D



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• SLOTTIME 0

• START $11

• STOP $13

• STREAMSW $7C

• STREAMCA OFF

• STREAMEV OFF

• SUPLIST

• SWP 17,17,108

• TELEMTRY 0

• TRACE OFF

• TRFLOW OFF

• TRIES 10

• TXDELAY 30

• TXFLOW OFF

• UNPROTO APKPC3 VIA WIDE

• UIDIGI ON RELAY,WIDE1-1,WIDE2-1,WIDE2-2

• UIDUPE 30

• UIDWAIT OFF

• UIFLOOD NONE,30, ID

• UITRACE NONE,30



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Hamcom 2005


• USERS 1

• XFLOW OFF

• XKCHKSUM OFF

• XKPOLLED OFF

• XMITLVL 100

• XMITOK ON

• XOFF $13

• XON $11



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Hamcom 2005

Recommendations: Home QTH

• For your own station, set via with real callsigns, not relay,wide

• In an urban area with a busy channel, consider turning your own digipeat function off. If stations can see a wide, save your transmitter and the channel’s throughput!

• If your station is enabled as a relay digipeater, use a tnc that provides callsign substitution



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Hamcom 2005

Best Resources for Info

• digis.txt file in the APRS DOS software by WB4APR

• Ongoing discussions on the TAPR SIGswww.tapr.org

• Local discussion boards

– TX APRS Yahoo group: http://groups.yahoo.com/group/ntx_aprs_ug/

– www.dfwaprs.net



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Hamcom 2005

Wrap-up• Help is sitting next to you

• Know your area coverage

• Establish goals for your Digi

• Use latest guidelines

• Minimize excessive traffic

• Automate and backup if possible

• Research before spending one dollar

• Spread the APRS Benefits message to others



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Hamcom 2005

Go forth and digipeat

APRS is a registered trademark Bob Bruninga, WB4APR Copyright © 2004 – John Beadles, N5OOM All Rights Reserved Hamcom 2005 Configuring APRS Digipeaters.

Documents

aprs aprs

aprs digipeaters

aprs packets

aprs station beacons

floor aprs resources

john beadles

n5oom slide

wb4apr copyright