David,
The way all of this came about was that I modelled a 0,1wave length boom
with out restriction
to the number of elements used and without restriction regarding in-line
height.
It was then a surprise to me that where gain was the priority the NEC
program evolved a design with
multi reflectors in quasi parabolic form with parallel elements such as I
mixed up smooth dish
thoughts with standard antenna array thoughts. Thus my search for info and
outside thought.
Now if I placed a constant current COIL in the feed dipole responses would
over whelm me
and place me in a position of immobility (smile)
Regards
Art

ssage ...

" wrote in
message
news:%Mwjd.10399$5K2.3472@attbi_s03...

"Dave" wrote in message
...
if the surface is large enough and conductive enough then the incident
waves
are reflected. note, this is a MUCH different effect than having
several
near 1/2 wave resonant 'reflectors' on a yagi.
Exactly, Which is why there is so little information regarding 1/2 wave
resonant VS
smooth surface reflectors. Modeling shows that it is possibly worth
while
to
concentrate solely on reflector capture via multi elements as opposed to
a
single reflector
and a long boom where as my previous investigation showed that
combination
multi element
directors and reflectors showed little advancement. If the drive element
is
multi banded then reflectors
would appear as full wave reflecters which would be an advantage.plus
providing the possible ability
for lesser beam width. I also have the feeling that grounding the
highest
element will remove local
static effects. First examination shows that feed position is not as
critical as that required
for smooth dish forms
Regards
Art

of course not, because you aren't reflecting. you are inducing currents
in
the elements and those currents add up in the direction you want. if you
really want to investigate this you should get one of the good modelling
programs and try it out in various arrangements.

Note, multiple reflector yagis have been around for ages. there are some
good reasons why they aren't common on hf... first they are hard to build
to
withstand weather. and second, the added performance on a relatively
short
hf yagi is minimal. when you get into very long vhf and uhf yagis it is
more common to see multiple reflectors, but they are mostly used to
eliminate specific side lobes... and even then the only common designs i
remember have a total of 3 reflectors, one on axis of the boom and one on
each side. a similar effect can be done with the so called 'quagi' where
you have a loop element as the reflector and maybe as a driven element
then
plane yagi type directors.