I`m still puzzled about "cluster antennas".

Best regards, Richard Harrison, KB5WZI

I really don't know why it puzzles you. I have determined that
coupling of elements which means parasitic coupling is wastfull. To
avoid this coupling one must have elements that are all resonant. This
means ofcourse that element dimensions are necessarily different from
neighboring elements so that coupling per se ( there is no attraction
or repeling actions between elements) removed which thus creates an
arrangement that is in equilibrium. When elements are associated with
each other one can call them a 'collection' of elements or a 'cluster'
of elements. Now with respect to efficiency this array does not have
coupling associated with reflectors and directors thus if the array
was energised then a far field of radiation is formed without any
wastefull interaction of particles between elements. So when the far
field is formed the only "waste" of energy is that created by skin
resistance which is easily calculated, since without interaction
between elements non radiating energy collision losses cannot occur.
If one is looking for efficiency one usually work with input energy
equals output energy plus losses. When one is examining the amount of
radiation formed in the far field because one does not want to get
into a situation of interactive bombardment of partcles that do not
contribut to radiation in the far field prior to the generation of
radiation. This analysis I suppose can be considered a simple
relationship with Poyntings vector and in a way provides support for
Poynting where none existed before but I may be over reaching there in
some eyes. Hope that satisfies your curiousity
Art