Log periodic antenna intuitions for its region properties
These are &quot;parasitic reflectors&quot; or &quot;parasitic elements.&quot;  They receive and reradiate the emissions from the active elements.  This does not add to the power output, of course, but the 360 degree round trip between elements causes them to reinforce and concentrate along the length of the antenna.  (The same thing happens on receive, but the power is coming from the remote antenna.)