In order for the Tracker to work, it must be connected to a GPS receiver producing live data, so
the receiver must have good visibility of the sky. Both Trackers provide an LED indication that
the GPS data is good: the TinyTrak has its own green light, whereas the OpenTracker flashes its
multi-function light once per second.
Setting audio levels
The Tracker’s audio output level is controlled by a pre-set potentiometer on the PCB. This must
be set for the correct modulation (FM deviation) level on the transceiver in use.
To do this, set the Tracker to transmit every 10 seconds, and whilst running the transmitter into a
dummy-load, monitor its output on another receiver. It’s easy enough to set the level “by ear”,
but if you wish to do it visually, try connecting the receiver to a PC sound-card, and use the
“Sine Wave” window in the “Sound Card Tuning Aid” of the AGW Packet Engine program.
The only other adjustment is to set the threshold of the noise detector: make sure that the LED
indicates when the receiver’s squelch is opened, and that it goes out when the channel is quiet.
On-air testing
Once everything is set up, have a look at the Tracker’s output off-air on your home-station APRS
receiver. If you don’t have one, or know any local stations who can check this for you, try taking
your Tracker system up to a local high-spot, and running it for half an hour or so. Then go back
home and have a look at an on-line APRS server, such as:
http://www.db0anf.de/app/aprs/stations
http://aprs.he.fi/?c=raw
Enter your callsign-SSID, and see if any of your packets have made it onto the network.
Incidentally, if you find that your indicated position is about 100 yards out, check the “Map
Datum” setting on your GPS: it should be set to “WGS84”, rather than “OSGB” for APRS work.
Burst-after-voice (PTT mode)
This mode is used when voice and APRS are used on a single shared channel. The APRS burst is
triggered by the release of the microphone’s PTT, and sounds a bit like a modulated pip-tone.
In order to use it, the microphone’s PTT must be connected to pin 8 on the Tracker, and different
settings used in the configuration. For more details, see this web-page:
http://homepage.ntlworld.com/jon.mossman1/digimodes/burst.html
Ross G6GVI
Version 4, July 2007
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Kommentare zu diesen Handbüchern