Andrew Nowicki <andrew@nospam.com> writes:

There is yet another option: a phased array
transmitter which makes only one narrow
microwave beam and changes its direction
every millisecond or so.

This is called the 'sequential' strategy in the SETI literature.
The advantages and disadvantages of this approach are discussed
in Chapter 5 of SETI 2020, under 'Strategies for Transmitters
and Receivers'.  Basically, if you think the receiver is using
a low sensitivity but omni-directional receiver, sending the
strongest signal you can in sequence to all the targets is best.
If they have a more sensitive but directional receiver (like ours)
then the steady illumination of all stars is best, even though
the power level must be much less in this case.  There are
intermediate strategies, too (illuminate M of N, and so on) and
they are good on some metrics as well.

    Lou Scheffer