Steve Nosko wrote:
"To change the phase, yes...To change the pattern. Probably not."

Certainly changing just the phase of the signal between two identical
driven elements makes an enormous difference in radiation pattern.

My newest copy of the ARRL Antenna Book is the 19th edition, but most
editions will have a figure similar to Fig 11 on page 8-8 of my copy.

The double-page figure is arranged into (8) vertical columns of
radiation patterns. Each column is for a different physical spacing
between the two parallel elements. All of the (5) patterns in a vertical
column have the same physical space between elements.

The only change between patterns in a vertical column is the phase angle
between the two elements. The top pattern is for 0-degrees between the
elements; they are fed in-phase. Other patterns are given for: 45, 90,
135, and 180-degrees electrical phasing between the two elements. It is
obvious that the pattern changes every time the phase between the
elements changes.

There are several ways to get the desired phase change. Roy Lewallen has
written an article in QST on the subject and has entered suggestions in
the ARRL Antenna Book. You can find them for yourself. Commercial arrays
often use a special T-network.

Best regards, Richard Harrison, KB5WZI