You can't go wrong by having an oversized ground. I understand that tapering the ground plane into the earth provides a better impedance match, althought I did not do that on our 10m site. I did make the plane larger than required, however and used several ground stakes on each side. I recall reading a paper >from HP about one of their sites where a fence existed far (relatively) outside their elipse. Yet, when the wind blew, variations in readings would be noted. So much for elipse theory. Richard Woods Sensormatic Electronics Tyco International -----Original Message----- From: [email protected] [mailto:[email protected]] Sent: Wednesday, June 18, 2003 8:13 PM To: [email protected] Subject: Question about OATS
Hello, I'm building an open area test site, and have some questions about the ellipse and ground plane. I'm following ANSI C63.7:1992. I have used several OATS and done site attenuation before, but this is the first time building one from the ground up. I'm building a 10 Meter OATS with a 14 foot turntable. Figure 1 in ANSI C63.7 says that the minor diameter of the ellipse shall be 17.3 Meters and the major diameter shall be 20 meters for a 10 meter site. For the ground plane, Table 1 in ANSI C63.7 says for a 10 meter site, the width shall be 12 meters and the length shall be 15.3 meters. The corners of the ground plane will be outside the ellipse. Is this ok, or should the ground plane be smaller, to fit inside the ellipse? What would be the minimum ground plane size I could use for this 10 meter site with a 14 foot turntable? Also, there is a chain-link fence running parallel with the proposed site, but the fence is just outside the ellipse. Would there be any problems with site attenuation? I can alter the ellipse so the site is not exactly parallel with the fence. (Antenna would be somewhat diagonal to the fence) Would that help avoid any problems? Thanks in advance for any input you may have. Tim Pierce EMC Engineer
