Timewave PK-900, Operating Manual

Page: 353 / 392

TNC GPS Upgrade Addendum/ 11111
GPS Operation
Overview
This chapter describes how to configure and connect your TNC for GPS operation.
Why do GPS in the TNC?
All Timewave TNCs can run with Automatic Packet Reporting System (APRS™) software.
The TNC, however, has special firmware which makes Stand Alone Tracking and Ultimeter II®
compatibility possible. Timewave also offers an APRS Adapter Cable for the TNC which makes
Hardware Single Port Mode (HSP) operation possible. The reason we chose to put special firm-
ware in the TNC and develop the APRS Adapter Cable for the TNC is because this TNC is per-
fect for going mobile; which is what Global Positioning Systems are all about.
The TNC contains special GPS features not found in other packet Terminal Node Controllers.
The TNC can detect whether or not a GPS receiver is connected with the GPSAuto command,
it then chooses the appropriate GPSMode of operation. If a GPS receiver is detected upon
power-up, the TNC automatically sends a GPS initialization string. The TNC can be remotely
polled by addressing a packet to its GPOLLCall, or by the polling features in APRS. The
TNC’s GPS commands can be remotely programmed using the GREMprog command which is
very convenient in Stand Alone Tracking applications—the unit never needs to be taken out of
the vehicle to change GPS settings. GPS receivers can be remotely programmed via the TNC.
The TNC’s internal time and date can be set from the information obtained from the GPS re-
ceiver. There are provisions for an external input to cause the sending of NMEA strings, such as
from a radio control head button. The TNC can even operate packet and GPS at the same time
using the commercial mode. See You’re in Command chaper, G section for GPS commands.
What is APRS?
Automatic Packet Reporting System
(APRS™) is a copyrighted software
program developed by Bob Bruninga
(WB4APR), which is distributed as
shareware for real-time Packet com-
munications. You can obtain a copy
of APRS from http://
w e b . u s n a . n a v y. m i l / ~ b r u n i n g a /
aprs.html. For higher level APRS ap-
plications you may need a registered
version of the software. The soft-
ware keeps lists of stations heard and
displays the locations of stations visually on a computerized map like the one in Figure 1. The
maps can be scaled from .5 to 2000 miles. Few of the maps are complete, however there are
tracking features built into APRS which allow you to create maps just by driving down the
streets of your town. Stations can appear on the maps and each station may be given a symbol
such as a house, car, or boat. The real benefit of using APRS software is in mobile tracking ap-
plications. Vehicles and people can be tracked and mapped using APRS. APRS also includes the
ability to send short messages and bulletins. Using Ultimeter II weather information can also be
shown on the computerized maps.
FIGURE 1: APRS computerized map
Mar. 2003 REV F