A 'Mint Idea' APRS Tracker
In
a perfect world, I would have a Kenwood TM-D700A dual-band mobile
transceiver with integrated packet data TNC and a Garmin V Street Pilot GPS unit custom
mounted in the console of a Ferrari 575M. In the real world, and in
the true spirit of Amateur Radio do-it-yourself experimenting, I settled for a less elaborate APRS tracker mounted in a
Ford Explorer.
If you are content with simply beaconing your position to the Automated
Position Reporting System
network, a
portable or mobile APRS tracker does not have to be an expensive proposition.
The project described here was built on a rainy weekend for a total cost of
under $100.
TinyTrak-II |
$33 |
Byonics N6BG |
Rand McNally Streetfinder
GPS |
$20 |
e-Bay auction |
Alinco DJ-110 2-meter
transceiver |
$40 |
Hamfest bargain table |
2-meter magnet mount antenna |
$5 |
Hamfest bargain table |
Misc. connectors, boxes,
hardware |
$0 |
Bench junk box |
TOTAL |
$98 |
Weekend Project |
TinyTrak-II, www.byonics.com,
is a GPS position
encoder which, when connected to a GPS and a radio, will transmit its location
at an adjustable rate. TinyTrak-II is a construction project providing an
inexpensive way to build a
mobile tracker without the need for a full TNC. TinyTrak-II
is personalized for your call sign by connecting to a computer's serial port and
running a simple configuration tool which allows setting of all user options. Construction consists of a hand-full of supplied components that must be
populated on the PC card and soldered. It can be completed in
under
an hour. Mounting in a suitable enclosure,
connection to a radio
transceiver, configuration and testing require additional planning and time.
There is an on-board mounted +5V regulator which allows powering from a variety
of external sources. I mounted the unit
in a tin Altoids Mints box to provide some measure of RF shielding and added a
DB-9 connector wired as a Kantronics KPC-3
compatible radio port. This allows easy interfacing to a transceiver using
common Kantronics data cables. This is consistent with the interfacing scheme
I've used for other digital data radio projects such as a PSK-31/packet sound card
interface and commercial TNCs.
The
12-channel OEM GPS board is manufactured by Talon Technology. The one I used was 'hacked'
from a Rand McNally Streetfinder GPS for Palm III. I removed the GPS board
and
passive antenna disk from the molded plastic case designed to attach to the
Palm III PDA. Then, I separated the Talon OEM GPS board from the Palm III data
port interface and battery charging PC board to which it was mated. Two minor
modifications are required to make the GPS self-start and run from an external
power supply. Complete instructions on how to 'hack' this unit can be found
at www.radiohound.com.
With a little experimenting I've found that the board will operate
satisfactorily from a supply voltage of +4.5V to +15V DC. This, like the
TinyTrak-II, allows for a wide range of power options for fixed, mobile and
portable operation.
I
mounted the GPS board and DB-9 connector in a tin Altoid
Mints box. This provides good RF shielding and antenna isolation. The GPS
antenna is mounted to the Altoid box top lid. The DB-9 connector is used to connect the GPS to a computer serial
port. For the time being,
until I come up with a permanent placement, the stacked boxes sit on the dash of
the SUV with the status LEDs positioned so I can monitor operation and channel activity.
The receiver is surprisingly
sensitive and the disk-shaped ‘patch’ antenna has a wide angle of view. When
the RS-232 level GPS receiver output is monitored from a notebook computer, it
is not uncommon for it to lock on eight or nine satellites. Four satellites are
required for true 3-D positioning.
I
used a PS-2 mouse/keyboard extension cable to connect the GPS to the TinyTrak-II.
I cut each connector end off leaving about 4” to 6” of cable attached, using
the male connector on the GPS side and female connector on the
TinyTrak-II side. When connected, ground and +12V power is supplied to
the GPS from the TinyTrak-II box and GPS data output is supplied to the TinyTrak-II
from the GPS box. The two boxes are attached to each other using Velcro strips.
When
the boxes are separated, I can insert the DB-9 connector on the GPS box directly
into the serial port of my notebook computer and plug the male PS-2 connector
into the PS-2/mouse connector on the notebook to draw +5V power for the GPS
board. This allows
use of the GPS with
UI-View, Rand McNally Streetfinder, DeLorme Street Atlas USA or other
APRS/GPS/mapping software running on the notebook computer. Alternately, I can
leave the GPS box attached to the TinyTrak-II box and connect a short serial
cable from the GPS to the notebook computer. This allows GPS position data to be
routed to both the notebook computer for real-time navigation and to the
TinyTrak-II which beacons my exact position to the APRS network. My son likes to play navigator in the shotgun seat of the SUV while I'm
driving, calling out intersections and points of interest from the mapping
software on the notebook computer.
These
links will give you more info on the GPS board.
Talon
Technology: http://www.talon.co.nz/
NAVMAN
review: http://www.gpsnuts.com/myGPS/GPS/Hardware
reviews/RandMcNally/rand_mcnally_gps.htm
The
Streetfinder GPS for Palm III units are now discontinued by Rand McNally, but
are regularly featured on numerous e-Bay auctions.
Average winning bid prices range from $20 - $40 US.

TinyTrak-II
Design
TinyTrak-II
Configuration Program

Recommended TinyTrak-II
Settings
Field
| Suggested Value
| Default
|
Callsign
| Your Callsign-SSID
| NOCALL |
*Digi Path (see below) | WIDE1-1,WIDE2-1 | WIDE3-3 |
Symbol
| Your choice
| - |
Table / Overlay
| Your choice
| / |
|
TIMING
| |
Keyup Delay (TXD)
| 300
| 250 |
Transmit Every
| 60
| 60 |
Quiet Time
| 1500
| 1500 |
Calibration
| 128
| 128 |
Status Beacon
| Your email address
| TinyTrakII |
Send Every
| 3
| 3 |
Transmit Altitude
| Checked
| Checked |
Only Send Valid Position
| Checked
| Checked |
|
MIC-E SETTINGS
| |
Enable
| Unchecked (unless you have a MIC-E)
| Checked |
|
TIME SLOTTING
| |
Enable
| Unchecked
| Unchecked |
|
SMART BEACONING
| |
Enable
| Checked
| Unchecked |
Min Turn Angle
| 27
| 27 |
Turn Slope
| 255
| 255 |
Min Turn Time
| 3
| 5 |
Slow Speed
| 10
| 2 |
Slow Rate
| 900
| 1800 |
Fast Speed
| 50
| 65 |
Fast Rate
| 60
| 90 |
*OPERATIONAL NOTES |
*Note: In October of
2003, Bob Bruninga, the creator and driving force behind APRS, proposed
a plan to "fix" APRS. In his paper
"Fixing
the 144.39 APRS Network - The New n-N Paradigm" he states:
"The purpose of this page is to
show how we can drastically improve the 144.39 network by simply getting
everyone to use the proper settings in their existing digis. The network
evolved over 13 years and some pretty bad settings are out there causing
tremendous inefficiencies. These can be fixed in most cases just by
remote-sysop adjustments of parameters without even a trip to the site.
We call this initiative the New-N Paradigm. These changes are
mostly transparent to users and it all boils down to one universal path
recommendation for all users. Use WIDEn-N where N is appropriate for
your area." I encourage everyone
operating an APRS mobile, fixed station or digi to read Bob's entire
proposal. The Digi path settings in this chart reflect the New n-N
Paradigm. Jim, N2IXD |
Click
Here to see my DigiTraker APRS project.
ã2002,
N2IXD
rev.050615
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