Very likely radar is in the middle of the launchers, from comments:

S-300/400 TEL have to stay close to the Radar for mainly two reasons.

The Radar vehicle also has the generator supplying the TELs with electricity.

and the even more important reason is that the radar data can only be transmited over a short distance so if the TEL is too far out it can't get data from the Radar anymore.

Edit: max range for a S-300 is 120m between the TELs and the Radar and since the S-400 is actually just a S-300PM3 its probably the same or at least very similar