That is part of the problem with the game. If you make it to where the ST Radar is listed, it will "kill" the SJ... So in actuality, it will not be visible, other than the over-sized periscope head, and "Radar contact:" reports that do not show on the A-Scope or the PPI, but do show on the NavMap when you raise the Observation Periscope while submerged. It is a vain attempt to not make it into a super-radar...
- You should still have a rotating SJ antenna (actually, the "Improved" SJ) - if it applied correctly. If it did not, you might have ST functionality that shows on the PPI, no rotating SJ antenna showing, but you do have the functioning radar... Available only on the Gato, Balao & Tench. However, it needed the conning tower upgrades to "attach" the new Observation Periscope to, but was very iffy on all but the Tench... The entire shmear is changed for the next release, and seems to function better - but still needs the conning tower upgrades... I very much detest the way SH4 does conning towers / turms... sigh