It depends on the system, often times they’ll have additional guidance assistance, such as an infrared seeker or some inertial posturing system. SARH just means the main guidance is provided by a seeker picking up radar from a external emitter painting the target. As supposed to ARH (active radar homing) where the missile has its own emitter and detector. Most systems aren’t just one thing these days, for the sake of redundancy and error correction.

Thats the idea behind datalink

Probably not with SARH, multiple emitter sources would just complicate the job of the detector on the missile. Like I’m sure it could be made to work with a bit of compensation, but it would add cost and complexity to the seeker on the missile, which sort of defeats the point of such a system being cheap and easy to build. There’s also the Possibility that the returns would be too diffuse for a detector on the missile to track beyond that 20km range, so having additional sets beyond that range wouldn’t help. Probably easier and cheaper just increase the range of a single radar. Just putting the whole set on a really big missile and making it an active radar homing system might make sense with an array of sets providing warning and an initial vector, and the missile guiding it’s self in, but again, now your missile is the cost of at least one set per launch.

Not sure what limits the range on this set, but they mention a wave guide improving it, which makes me think it’s just a power limitation on the emitter or limited sensitivity on the receiver.