The 3 beeps you hear are probably the repeater. With MXT500 you have to turn on repeater channels. Find privacy codes for transmit and recieve. (TSO or DCS) Menu.
I have been learning, but think if you search the tube... MIDLAND MTX500 it may be some help.
I am also very interested in a PACNW Net. I see that we have two National Net repeaters showing on MyGMRS in Washington State, but none in Oregon showing on the map.