calling the longer element 'behind' the driven element of a yagi a
'reflector' is poor terminology. it does not actually 'reflect' it just
resonates at a slightly different point and the combination of phase and
distance from the driven element contribute to the gain in the 'forward'
direction and cancel out signals in the 'backward' direction. actual
reflection requires a conductive surface several wavelengths long in all
directions as is done on parabolic dishes for microwave use. even when you
look at vhf/uhf yagi's that have multiple reflectors they are still only
using the phase shift of the resonance of them to add or cancel energy from
certain directions. the smallest one that might be really called a
reflector is the 'corner reflector' antenna sometimes used at vhf and uhf.

" wrote in message
news:uEfjd.579123$8_6.52336@attbi_s04...
For ham radio it is conventional ( my thoughts) to see reflectors as
element/s placed behind
a feed element where. like other elements in an array receive radio
energy
and then reradiate a portion of the received energy.If one wants to
emulate
a point
radiation then many elements have to be arranged in parabolic fashion such
that all R.F.
received or transmitted meet at a common point.

Now I really know didly #####about dishes as my world is made up from
Yagis
but now
I am starting to think about these things which really raises questions
about what I had previously accepted
For instance,
1
Commercial dishes are not made of reflectors with a fraction of a wave
length ( surface is smooth)
So we have some how shifted from 'resonation' to a 'reflection' mode as in
light even tho a resonance
must still some how occur, but how and with what length reflectors (
multiple long wires?)?
2
If radiation/reception follows a common path then is the dual path
radiation
as seen with a Yagi (90 degrees apart)
changed ?
3
What would the result be if multiple electrical connection lines were made
between the horizontal reflectors (vert refl form)?

The emergency operation is now over after a lousy week in hospital but I
am
grounded for the rest of the year
( pain and infections and physical inabilities) books and the like is a
hard task but the laptop is at hand if I can find suitable links to study.

Plans are complete and parts available for a 20 metre dipole with eight
reflectors set in quasi parabolic form to deliver
14.5 dbi.BW 63 degrees which I hope then to reduce to 30 degrees for added
gain.
Feed dipole will be of variable length for different band use.
Isn't experimentation great when failure is not considered disasterous to
ones self esteem and resume?

Regards
Art