Consult C63.7, "Guide for Construction of Open-Area Test Sites. We built our site according to the guidelines with two exceptions: we soldered the ground plane sections at about 6 inches and we made the plane size slightly larger than the recommendations. We passed the first time. I recommend the increased size.
Raising your ground plane above ground level is not recommended as it tends
to create ground discontinuities at the edge of the plane. For example, this
can be a problem for OATS on top of buildings. This problem can be corrected
by increasing the size of the plane.
We run our cables over the ground plane and do not have a problem.
Our OATS is in on the edge of a woods with trees on two sides and water on
two sides. On the water sides, we have bushes to "hide" the site (required
by the building code). We have not noticed a problem.
Re how far way an object must be: I saw a film produced by HP where they had
a metal fence far outside the ellipse. They claimed that they could see
variations in the reading when the wind moved the fence.
----------
From: [email protected]
[SMTP:[email protected]] on behalf of Flinders, Randall
Sent: Wednesday, November 11, 1998 12:44 PM
To: 'emc-pstc'
Subject: ANSI C63.4
Greetings EMC Professionals!
We have a 10 Meter Open Area Test Site in our parking lot.
The Ground Plane is covered by 3 inches of concrete, and measures 29.4
meters by 7.9 meters. There are several planters within the 2R x 1.73R
10-Meter ellipse as described in ANSI C63.4. The Power and Signal Coax are
run along the top of the ground plane, as underground installation is not an
option. I am attempting to improve the performance of this site. The
alterations I am considering are:
1) Installing a solid ground plane on TOP of the concrete.
2) Extending the width of the ground plane to 11.4 meters.
I have four questions to pose to the group:
Question #1 - Does anyone have experience with an OATS where
the ground plane is covered with concrete? What effect does this have on
the performance of the site?
Question #2 - ANSI C63.4:1992 does not specify the minimum
size of the ground plane. Is there a guideline, or can someone tell me from
experience, what the minimum size should be?
Question #3 - Does anyone have any feelings on what the
effect of running the COAX and Power Cables on top of the Ground Plane can
have on the site performance? Would It be better to raise the ground plane
off the ground (on a wooded platform) in order to run all of the cables
under the GRP?
Question #4 - Although there are several trees with in the
10 meter Ellipse, they are located at the very edges of the Ellipse.
However, there are raised concrete curb planters and waist-high hedges that
are well within the Ellipse. Can I expect these items to cause significant
site abnormalities? Also, how far away does a metal object need to be
before I can consider it safe from causing abnormalities due to reflections?
Any insight or suggestions on this matter would be greatly
appreciated. Thanks for your time.
Regards,
Randy Flinders
EMC Engineer
Emulex Network Systems
(714) 513-8012
[email protected]
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