Louis Scheffer wrote:

See Appendix B, pages 303-320, of the book SETI 2020.

I will. It is called 'Omnidirectional SETI System'.

This is *exactly* what a phased array transmitter does,
except it generates the radiation locally at each point,
rather than by scattering coherent radiation from a central
source...

It seems feasible and versatile, but more expensive than
the hologram.

PS. I have just learned from the web that in the 1960's
the Soviet Union dominated SETI, and it used nearly
omnidirectional receiver antennas. I have no idea how
these antennas were designed.

Criticism of SETI in Wikipedia:
http://en.wikipedia.org/wiki/SETI#Criticism_of_SETI