Argent Data Systems
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Audio levels
Proper audio levels are critical for reliable transmitting (TX) and receiving (RX) of data packets.
For normal APRS operation, the tracker’s RX audio level setting isn’t critical - you can leave it set
at its maximum. For certain voice features you’ll need to adjust it to match the peak audio level
coming from the radio. If the radio doesn’t have a fixed level audio output, make sure you set
its volume such that the level does not exceed the tracker’s maximum of 3 volts peak-to-peak or
clipping will occur and degrade receive performance.
The TX audio level setting is particularly important. Failure to set the TX audio level properly is the
most common cause of readability problems. The correct level setting will depend on your radio.
Setting the level too low will result in a weak signal that’s easily lost in noise. Setting it too high will
cause distortion that will render packets difficult or impossible to decode.
For typical APRS operation on the 2-meter band, a proper TX audio level setting is one that results
in an FM deviation of about 3.0 to 3.5 kHz. Ideally this should be set with a service monitor or
deviation meter. If you don’t have equipment to measure the deviation directly, use another radio
to listen to the tracker’s transmitted packets. Start low and increase the TX audio level setting
until the apparent loudness doesn’t increase anymore, and then back it off by 10-20%.
Status LEDs
Two LEDs on the front panel provide various status indications. The TX/RX LED lights red when
transmitting and green when receiving. ACT blinks green when a valid GPS fix is received or red if
the fix is invalid.
File System
The tracker’s file system can be used for storing scripts, logs, and voice announcements, among
other things. Approximately 24 MB of storage space is available. The file system is used for
temporary storage of downloaded updates, but otherwise its contents are not needed for normal
operation of the device - the file system can be wiped and reformatted at any time without
affecting operation, as the firmware and configuration data are stored outside of this file area.
