Why wasn't the RADAR ever updated?

[PhantomHans]

So, I just have to ask, why wasn't the radar ever updated by most end users?

If I understand correctly, the F-4J and S got a pulse doppler radar.  But the F-4B,C,D,E,F,G, and N, other than those few later updated with modern radar by foreign users, did not get any updates.

 

As a side note, I understand the B,C,D, and N had a different radar than the APQ-120 but other than perhaps longer range due to the bigger dish I understand it to be quite similar?

I have no idea what the British F-4K/M had.

Seems kinda odd to me though as the radar is the one part of the jet that, at times, really seems to be lacking and hasn't been improved by the time of our E model.

[Ivandrov]

I'll talk mostly within the scope of the F-4E. But, usually the primary reason is money.

 

To be clear. The APQ-120 was actually upgraded, up to a v9, I believe.

But, given a certain budget, you can spend that money upgrading old airframes to fit the new radars (It's not just a matter of swapping dishes, often the radar is designed to fit the airframe not only in terms of size but things like power draw, and the weapons control systems) or you can just shove the new tech into a new airframe.

 

Of course, you have to realize that these are old airframes that might be reaching retirement anyway, with increasing maintenance costs.

 

The ones who continued to update the old airframes are usually the ones that can't really confidently meet the upfront cost of new ones. So, you're only left with the option of upgrade.

Edited 12 hours ago by Ivandrov