Currently the APG-81 can detect targets of 10 sq m from a distance of around 250 km. If the head-on RCS of the Chengdu J-20 is to be around the same as the F-22, at between -20 and -30 decibels, then the APG-81 could detect it at a distance of 20-40 km. The F-35 is also equipped with a photoelectric sensor, the range and resolution of which is unclear, but likely of higher quality than the Low Altitude Navigation and Targeting Infrared for Night (LANTIRN) installed in US third-generation fighters. The fire-control radar on board third-generation fighters have no electronic interference capabilities, so an on board electronic jammer has to be used on board. As there is little space for an antenna and a high-frequency transmitter, this falls short of fire-control radar by a long shot, whereas the APG-81 uses the long range radar itself to engage in electronic interference. As the APG-81 has average power of 2 kW for interference, it beats the radar on board the third-generation fighter, at just several hundred Watts, right out of the water. At long-ranges the radar on third generation fighters is left only with its goniometric function, losing the ability to measure distance at all. This, in turn, leads to a loss of target tracking capabilities and its ability to visually simulate attack, which renders it ineffective.
East Asia Disputes: Threats and Countermeasures
Before 2016, the JSF may only be able to buy a few pre-production versions of the conventional takeoff and landing (CTOL) variant of the F-35, the F-35A, to engage in flight tests and will likely only receive the final version of the F-35A a few years down the line. Countries are cooperating in the manufacturing and testing stage of the F-35's development in different ways. The UK agreed to invest funds of 10% or US$2 billion, under the JAST (now JSF) program office, which grants it priority access to F-35 equipment. The second way is through an investment of 5% or US$1 billion, through which Italy and the Netherlands are participating in the project. The third way is as a mid-ranking representative, under which participant countries can only make demands for custom details and invest funds of 1% or US$200-400 million. Countries who have chosen to participate in this way included Turkey, Canada and Australia. Later two more categories of participation were added. Those in the fourth category have to pay at least US$75 million. There are 12 potential countries that may sign up for this. Israel is the only country in the fifth category, under which it needs to pay US$2 million to access data on the F-35 project. Given the above division of categories, Japan will only be able to take part in the project under the fourth category, which means that at least eight countries will have priority in buying the F-35 aircraft and equipment before Japan. In addition to this, Japan is only buying around 40 F-35A fighters, a relatively small order, which makes it unlikely that it will get quick delivery on its order, compared to those willing to order more. Japan will likely get permission to assemble the F-35A after 2020, which means that the finished aircraft will come off the production line a lot later. Whether or not Japan is granted the right to assemble also depends on Japan's finances and on the stability in the country's relationship with the US.
Given the time frame for Japan's potential purchase of the F-35A aircraft and Japan's announcement of a project to develop its JASDF, by around 2025, the JASDF will likely have the following equipment and weapons systems: six E-767 early warning aircraft, around 40 F-35A fighters, around 100 upgraded Mitsubishi F-15J/DJ Eagle fighters and 150 Mitsubishi F-2 multirole fighters. Japan's air defense zones are divided into three areas, north, central and west. The north zone is aimed at defending against aircraft from Russia; the west zone is aimed at defending against aircraft from China, while the central zone gives Japan strategic flexibility in deployments. This means it is likely that the F-35A fighters will be divided into two squadrons, with 20 being deployed to the west air defense zone and 20 being deployed to the north air defense zone. Two F-15J fighters and one F-2 from the central air defense zone will likely be deployed to the west and north air defense zones, while the rest of the aircraft will serve as strategic reserves in the central defense zone. This will mean that Japan will have fallen far from its title as the No. 1 air force in Asia that it proclaimed in the 1990s.