Tim Pierce wrote >> I have worked with sites that used the hardware cloth (screen) over concrete in the past. When the tears would happen, they would patch that area ...<<
Tim, If this were a reflector antenna, holes in the reflector would be kept to 0.1 wavelength at the highest frequency. This results -- if reflections are only from the defined surface -- in a loss to feed-through of 1 dB. Keeping surface irregularities to less than one eight wavelength insures the phase of reflected signals is accurate enough to keep the resultant within about 1 dB of the maximum possible, too. If we take 1 dB for each of these effects, we might use up half of our error budget for an FCC site. However, when considered as a reflector, it appears the care we lavish on much of our ground plane is unneeded. Try ray-tracing the site to see what I mean; where horizontal polarization is used, areas near the EUT and the receiving antenna don't generate any reflections between EUT and antenna. They would affect propagation of vertically polarized signals at the lower frequencies. This suggests that we need to take more care near the middle two-thirds or so of our sites than near the EUT and antenna. I don't recall seeing any papers on thinning a ground plane away from areas supporting reflections, though Speeding up the process? Well, when broadband antennas are used you can semi-automate the procedure. OATS being subject to ambients, and max hold being unintelligent about what it holds ON, an operator is needed to be sure erroneous data points aren't collected. I suppose a modulated signal could be used, and results taken through a narrow band detector, reducing the probability of ambients being taken for data, but most of us prefer to stay as close to agency-accepted methods as possible. The signal generator is another matter, as many are controllable remotely -- or you can use a tracking generator or network analyzer. If you have enough RF, or use a post-generator amplifier, you can locate ALL your equipment in the control room. Of course we are limited to Part 15 levels for all this. Cortland This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
