Commercial and Military divers like to have alternate channels they can choose in the event two or more teams are operating in the same area. How many watts a transceiver has usually dictates how far it will transmit. Our SSB-2010 is a 3 watt transceiver and have achieved ranges up to 1000 yards. Our SSB-1001M is a 5 watt transceiver with ranges reported out to 3000 meters in good conditions. Our Magnacom is a 30 watt transceiver and ranges out to 5 miles were reported.
Batteries are necessary to support power.
In some cases, its the battery that dictates the size of the unit. Electronics can be made tiny as well as the housing. However, batteries required to support the range and longevity cause the housings to grow in size. Todays battery technology is getting better, but still not what we would like to see. A few examples of what we are up against, to make a Military unit with a 3,000 meter range, we had to use a double Metal Hydride AA battery pack.