On Wed, 13 Jul 2016 23:29:17 +0100, Netko
wrote:

The 737 MAX which has been flying at Farnborough this week has a lump on its
back, arrowed in the upper part of the attached picture. I assume this is a
fairing for the Ku-Band antenna. However, it seems a retrograde step when
compared with the streamlined design on the aircraft as originally rolled out
(lower part of the picture).

Anyone know why the change was made?

I'm not convinced there is a difference - looks more like different
perspectives of the same shape. The factory shot sideview doesn't
show the width of the more-or-less constant cross-section of the dome.