The Soviet ARM, AS-11 required quite a sophisticated aircraft to operate it including a sensor pod to locate the targets before launch... the missile knew the physical location of the target before launch so if the source turned off it could still hit the location and with a 150kg blast warhead most of the time the antenna would be damaged and taken out even if the system turned off immediately after launch.
The new model is slimmer and designed to be carried internally on the PAK FA and also has IR sensors fitted... most large radars generate a lot of heat when operating so the sensor in the nose can detect and track the radar signal while the IR sensors detect its IR signature... if the radar turns off it can continue to home in on the fading IR signature and still get a direct hit... very clever.
HARM has only recently gotten GPS assistance, in the past if the radar turned off they missed. They were only used for suppression of enemy defences rather than the destruction of enemy air defences (ie SEAD rather than DEAD), so their purpose was not to destroy SAMs but to make them turn off so the aircraft could fly past safely... of course with modern TOR and Pantsir systems and various passive sensors to detect aircraft and cruise missiles making them turn their radars off was not good enough to make western aircraft safe any more so they had to change from SEAD to DEAD.
Most Russian SAMs can shoot down ARMs so they would not shut down their radars they would simply allocate a missile or two with dealing with any ARMs detected... and continue normal operations. Systems like S-350 and BUK-M3 use 12 missiles on each launcher to engage an increased number of aircraft and munitions.
I know its Easter but resurrecting a 7 year old post just to comment on it?
Well the alternative is to open a brand new thread on the same topic which I think personally would be the worse option.
BTW regarding the retirement of the ALARM...
It added: "UK armed forces have a range of capabilities that can be used to counter enemy air defence, including kinetic strikes via long-range cruise missiles, such as Tomahawk and Storm Shadow, and a multitude of highly effective precision air-to-ground weapons.
"Additionally, it is likely that we will work with our international partners on future major operations overseas and will therefore manage all of our capabilities as part of that coalition."
In other words we are going to use American missiles instead of British ones that are better... Blue Streak anyone?
ALARM was probably the most clever western ARM... it could be used in a range of modes including one mode where you fired it into a region you were about to fly through where it climbed up to very high altitude and then deployed a parachute and slowly descended while your aircraft or missiles flew through... any radars light up and it cuts the parachute and lights up a rocket motor and accelerates down to hit the radar... very clever... much more sophisticated than Shrike or HARM.