>Hi all
>What happens to the takeoff angle of a vee beam or rhombic
>when it is constructed on the side of a hill. If it is pointed downhill,
>is the angle smaller (to horizontal) thereby making it a better dx antenna
>than if it was over flat ground?
>Bill W5EC
>
If the antenna is pointed perpendicular to vertical, then yes, the
radiation angle , depending on the actual slope angle, and distance will
favor lower angles. The degree of improvement depends largely on the angle
of the slope. This, in it's best case may mean a 6dB ground reflection
addition to the direct ray at some angles. I would doubt that it ever comes
to 6dB due to losses etc.
If you talk about actually POINTING the antenna DOWN as in tilting, then
NO, you have effectively cancelled your ground reflection gains. If you
think of the ground reflection as an IMAGE antenna placed at a distance
below ground the same us the real antenna is ABOVE the ground- then it
becomes more understandable. Since when you tilt an antenna DOWN above the
ground, the effective image antenna (mirror image) is tilted UP, thus
cancelling the gains you would have had without the image antenna (or
reflected ray).
Keep in mind too, that the ground reflection addition is only good for
certain condx in terrain. If the ground slopses too quickly, then the
reflected ray may have travelled simply too far, and when it returns to
combine with a direct ray, it may be now out of phase, cancelling much low
angle response.
Anyway, that's my two cents worth.
73 de Shawn
VE6PV
lightfol@cadvision.com
Suggested Serving, Antennas not included.
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