Good question, I don't know if that's it or not. I don't seem to see anything changing on the display but admittedly I'm not usually close enough to look carefully because its random and not telling when it will go off. Seems to happen once a day in no particular place on the water. The "alarm" is a high pitch fast ring that lasts maybe 2 seconds or so.
It does sound like your GPS loss of signal alarm. The radio default is “Loss of GPS Signal” alarm is set to on. You can turn it off
This is from the manual:
GPS alert setting
BUDDY LIST
LOCAL/DIST
USA/INT/CAN
>GPS/DATA
GPS/DATA
MANUAL
>SETTING
SETTING
TIME DISPLY
LL DISPLAY
>GPS ALERT
GPS ALERT
>ON
OFF
The GPS alert is usually set to ON so that if the GPS navigation receiver is disconnected, warning alarm beeps sound.
1. Move the cursor to GPS/DATA and press >ENT.
2. Move the cursor to SETTING and press >ENT.
3. Scroll through the GPS/DATA menu to GPS ALERT and press >ENT again.
4. Press >ENT again to have the GPS alert ON OR move the cursor to OFF and then press <ENT to turn it off.