I've noticed several sites (and books) show screen reflectors for
various multiple driven element broadside arrays, but I have not seen
any dimensions given for a screen reflector. I am aware that a
parasitic reflector for a yagi is about 5% longer than the driven
element. Is the same true for a screen reflector for a broadside
array like the Lazy H antenna?

For instance, since the total length for the two top horizontal 1/2
wave elements in a Lazy H are generally 1 wavelength long plus the
width of the center insulator does that mean a screen reflector should
be roughly 5% longer than the total side to side width of the Lazy H
antenna? Also is the best spacing between the Lazy H and the screen
reflector the typical 0.2 wavelength shown for a Yagi beam antenna
driven element and the parasitic reflector? If not is there a formula
for determining the width and height of the screen reflector as well
as the spacing between the Lazy H and the screen reflector for a
broadside array like a Lazy H?

Thanks,

Michael Rawls
KS4HY

On 6/8/2011 7:37 AM, Michael wrote:
I've noticed several sites (and books) show screen reflectors for
various multiple driven element broadside arrays, but I have not seen
any dimensions given for a screen reflector. I am aware that a
parasitic reflector for a yagi is about 5% longer than the driven
element. Is the same true for a screen reflector for a broadside
array like the Lazy H antenna?


Screen reflectors aren't critical in terms of size.. bigger is better,
of course, and there's some sort of point of diminishing returns, but
basically, it's providing some approximation of a "infinite perfectly
conducting plane"... Sort of like a counterpoise for a vertical monopole..


Now, one could greatly reduce the amount of wire needed at the expense
of bandwidth, etc., by putting a tuned reflector in, as you've noted.