[ETR3(SS)]

SH4 was based off of SH3, SH3 used a new engine and had no carry over from SH2.

That said, SH3 was designed with the Uboats in mind and their associated technology. SH4 was built off of SH3 directly. Not an unheard of way of game development except in this case the dev team that made SH3 didn't all move on to make SH4. This was apparent upon release when the game was a **** show of bugs, broken mechanics, and legal technicalities. Digging into the game files you'll find most of the SH3 files present in the SH4 install, although I haven't tested it I'm nearly certain you could run both from the same install somehow.

Now PB is correct in stating there are 3 commands for raising/lowering masts in SH4, because that's what we had from SH3. The last one wasn't a radar mast however, but was the snorkel. The ability to raise/lower a snorkel was implemented in SH3 and worked as intended (changed out the air inside and provided air for the diesels to run). The fleet boats didn't have snorkels and so this was left unused, but still present in the game (albeit a broken mechanic now).

This mechanic was discovered and used to raise/lower the SD radar instead by modder Anvart IIRC. This added some needed historical accuracy to the game. Now as for the SJ radar, I've not known it to be an extensible mast during the war. Later versions on the GUPPY boats may have been, but that was due to the larger conning towers. The SJ radar could however be used while submerged by coming shallow enough that the periscope shears cleared the surface.