When can I get surface radar??????

[Ichthyos]

You should be able to buy it with Renown, probably in early - mid 1942.

just to confirm:

I got offered sj radar in june, and sj1 in July at Pearl. might be a month or two lag in SE Asia core.

it's definitely very nice, and extends my detection range by nearly 50%.

Edit:

actually, I just got transferred back to Fremantle (to get a Balao), and there was no SJ1 upgrade there, but the standard SJ comes already equipped on the Balao.