Re: NEC-LIST:Progation at around 1 GHz

At 11:47 AM +0200 9/30/02, zvi frank wrote:
>I have a communication link around 1 Ghz. At one end I have a
>directional antenna and the other end I have an omni low gain antenna. I
>find in general although I have line of sight communication , I
>still get a lower signal than expected for free space....

0. This thread belongs on the propagation list, not the NEC list.

1. The polarizations of your antennas match -- yes?

2. Is your "omni" antenna a "ground-plane" type? If so, its gain in
the horizontal plane is very low. Replace it with an antenna having
no ground-plane.

3. Most likely you have strong interference between the direct
line-of-sight wave and a wave reflected/scattered from the ground.
By what angle(s) are these two (direct & reflected) paths separated
as viewed from either antenna? You must use an antenna (preferably
at both ends of the path) whose gain in the direction of the
line-of-sight is significantly higher than its gain in the direction
of the ground-reflected path. If you must use an azimuthally omni
antenna at one end, then use a vertical collinear array, the taller
the better. There are available and widely used commercially.

-Chuck

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