The Israeli AWACS carries a Phalcon conformal (it is built into the lower fuselage) phased array radar, SIGINT equipment (to capture and analyze enemy electronic transmissions) and a communications system that can handle satellite signals as well as a wide array of other transmissions. There are six personnel on board to handle all this gear, plus the flight crew.
The Gulfstream G-550 can stay in the air for over twelve hours per sortie, and can fly at up to 51,000 feet. It's a larger version of the Gulfstream G400, which the U.S. Army uses as the C-20H transport. The U.S. Coast Guard, Air Force and Navy also use militarized Gulfstreams. The 96 foot long aircraft has two engines and was built for long flights (over 11,000 kilometers). Current Gulfstream G500s cost about $40 million each.
The Phalcon radar is, in some respects, superior to the one used in the American AWACS. For example, Phalcon uses a phased array radar (thousands of small radar transmitters are fitted underneath the aircraft). The phased array radar, in combination with the latest, most powerful computers, and other antennas for picking up a variety of signals, enables Phalcon to be more aware of what electronic equipment (airborne or on the ground) is operating up to 400 kilometers away. The phased array radar allows positions of aircraft on operator screens to be updated every 2-4 seconds, rather than every 20-40 seconds as is the case on the United States AWACS (which uses a rotating radar in a radome atop the aircraft.) The first Phalcon system was fitted on a Boeing 707, although somewhat limited versions could be put onto a C-130. On a larger aircraft, you can have more computers, and other electronics, as well as more human operators. But the major advantage of the Phalcon is that it is a more modern design. The U.S. AWACS is over twenty years old and has undergone upgrades to the original equipment. The Israeli air force operates six Phalcon aircraft (using Boeing 707 airframes).
Israel put its first new-generation AWACS (Airborne Early Warning Aircraft) into service. Using a long range business jet (the 40 ton Gulfstream G500) and Israeli made radar and electronics, the same aircraft is being offered to South Korea. This contract is worth $1.5 billion, for four new ISR (Intelligence, Surveillance, Reconnaissance) aircraft. Israel has already sold a similar system to India, with the equipment installed aboard a Russian Il-50/76 aircraft.