Using the iX3M / iX3M2 / iDive I have to stay very close to the transmitter to get the pressure tank value.
When the iX3M / iX3M2 / iDive is outside of the water its radio power is automatically reduced to save battery and to avoid interferences coming form other radio sources.
When iX3M / iX3M2 / iDive detects that the dive has stared it automatically increases the radio power. So if you are not diving you need to place the transmitters very close to the iX3M / iX3M2 / iDive to get the signal.