Bill Turner wrote:

Trying to bridge the gap between engineering and English, I would
suggest this analogy:

A mirror reflects light energy fed to it, while a light bulb takes
electricity and turns it into light.


A reflector does not "reflect". It simply re-radiates with the correct
phase and level to null energy from the other element(s) in the
unwanted direction. This is why spacing and length is critical.

Try using your two element Yagi with a reflector lower in frequency.
The reflector becomes a director.

Now think of a director. The director removes signal from the rear
about the same as a "reflector" does. Change the length and it can
become a reflector.

Now think of a mirror or a screen that is not resonant.

A mirror or screen works on a different principle. It reflects. Once it
is a certain physical size, resonance does not matter. It can be 100
wavelengths across or 1 wavelength, and it still reflects. It will
reflect infared or ultraviolate, and a 100 foot screen will reflect 60
meters to 10 cm all the same if the mesh is small enough.

Thinking a reflector "reflects" and a director "directs" will doom you
to failure if you are trying to understand how a Yagi works.

73 Tom