8-element butler array spacing
 

the scanning beam of butler arrays is affected by its antenna
"free-space" spacing.
im developing an 8-butler patch-based antenna array using an fr4 board
with er=4.2 and T=1.6mm with loss of .03...
im having problem with dimension so i squeezed the antenna element
spacing to its equivalent "guided" wavelength....
my questions ahow will this board guided spacing affects my
radiation pattern?i'd like to go for RT duroid boards with er=10.2 but
its very expensive..
any ideas to workaounr with my fr4 board?

thanks