Turn C/Ku Band TX/RX Antenna into X Band Antenna

We have a Large C/Ku Band TX/RX Antenna and want to convert it to a
S Band TX +X Band RX System.
Can we do this by only changing the Feed System or should we take other factors into consideration?

Yes, you can use the C/Ku dish antenna for S-band, just replacing the feedhorn, and keep the same focal point.

I guess the gain will be lower at lower freq ( S and X band) but you can still use the approach if gain loss is acceptable.