Hello Andrej,

Yes, situation is a bit confusing when speaking about the SM radar and its derivatives SM-1 and SP.
In his book "Naval Radar" Norman Friedman says that SM had a 2.44m diameter round dish antenna. 23 sets built through October 1944 and found on carriers.
Then came the lighter version SM-1 with a 1.83m diameter radar antenna with a slightly different shape. 26 built for the Royal Navy. There is a drawing in Friedman's book of SM-1 with IFF dipoles on center of dish. So far, no IFF mattress array on top dish in the photo of HMS Boxer I have.
Then came SP, with almost the same antenna as SM-1, but with an IFF array on top on . What is now confusing is that legend of photo on page 48 of Naval Radar says it is a SP radar with full IFF system (Mk.III dipoles on the frames protuding from the dish, and Mk.IV mattress above the dish) that I think is correct, while
the very same photo on page 39 of Alan Raven's Essex class carriers, says it is a SM radar !
So, a bit difficult problem to solve!
Meow!!
Ben