Not to rain on the parade, but be careful when comparing semi-anechoic chambers versus OATS that are of different distances, i.e. 3m vs. 10m. You may get not only widely different measurements even when compensating for the distances, but you may also obtain different frequencies. On two occasions, I've had frequencies show up rather prominently in the chamber prescan not to be seen to any significance at an OATS.
In other words, to get a fairly reliable comparison between a chamber and a site, in my opinion, you'll first have to compare a 10m chamber with a 10m OATS. Then, work backwards to a 3m chamber. You will also have to develop a fudge factor for the size of the EUT. The size can effect results as well. You may get good correlation with a small tabletop EUT and terrible correlation to a much larger device. Possible reasons for this I'll leave to discussion. But suffice it to say, the closer the product is to a point source the better the correlation. The farther the product is from a point source, the worse the correlation. At least in my experience. Name the site with which you will be getting an official measurement as your standard, then work all the others in reference to it. The standard site will be the one which will have the final say. Sorta been there ... Done that ... etc ... Sorta gave up. - Doug McKean ------------------------------------------- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
