Back in 1975, Boeing modified 707s to become AWACS involved intrusions of 18 inches deep into the fuselage. The rotodome was 30ft in diameter and weighed nearly 12,000 lbs. The mounting struts, designed to minimized aerodynamics wake over the entire tail section, added another 3,000 lbs. The turntable bearing assembly added about 2,300 lbs, it must rotated at 1/4 rpm even when the system is in non-transmit mode to keep lubricated. The entire structural support system must be doubly redundant to minimize the possibility of a mechanical failure, fatigue or combat, that would result in radome separation, which of course would be catastrophic for the aircraft. The summed up weight figure is only static, meaning stationary, load. Aerodynamic stresses in flight and maneuvers required the entire system to be mechanically overbuilt by %10 according to some conservative estimates.
The installation of an AESA array would lighten the load since there is no need for the turntable bearing assembly but the gains were not deemed to be overwhelmingly supportive to continue using the domed configuration. Improved AESA technology compelled the creation of the Saab's two-sided AESA array configuration. True...This configuration is limited to only 240 deg total coverage with degraded performance for each array at the 45 deg off-beam point and beyond. But the double-sided linear configuration allowed a much lower cost alternative, in purchase and long term maintenance, since the aircraft itself would not be an 'intercontinental' class aircraft like the 707. Lower cost also mean more numbers that can be deployed and that also equate to increased tactical flexibility. A paired and datalinked linear double-sided AWACS would offer the same coverage capability as the larger triple-sided dome but would have the ability to break off the pairing to respond to emergencies.