On Tue, 27 Apr 1999 14:58:30 -0400, "WOODS, RICHARD" <[email protected]> wrote: >You cannot perform a characterization that will mean anything. The room will >have standing waves that will be strongly dependant upon the size and >placement of the unit under test, the placement of the antenna and the >frequency. That was the plan - record frequencies where the room is unreliable, so we don't spend time looking at that data. Real tests would be done at an OATS.
My boss is interested in adding a screen room, but I'm worried that resonances will render the room worthless. In light of that, do you think I'd be better off developing a 'parking lot procedure', and figure out how to deal with the ambients? >The best that you can do is perform a pretest to find the >frequencies of interest then move to the OATS for a final test. A screen >room can be used for before and after comparison of EMI fixes, as long as >the unit under test is not moved. But once you have a fix, you will still >have to test on the OATS. Actually, you can perform diagnostic tests in a >lab if you set the antenna 1 m away. Just keep other sources a few meters >away from the antenna. > >To do what you want to do, you will need a compact semi-anechoic chamber at >a cost of about $140, 000 including the turn table. We just started using >one that complies with the NSA test given the constrant that we can't run >the antenna up to 4 m. We have found up to 6 dB of variation between the >chamber and the OATS. However the variation is small enough that we pretest >and fix in the chamber and only move to the OATS once we have confidence >that we have at least 6 dB of margin. So far so good, but I don't doubt that >some day we will end up out of compliance at the OATS even with 6 dB of >margin in the chamber. > > ---------- > From: [email protected] [SMTP:[email protected]] > Sent: Tuesday, April 27, 1999 12:22 PM > To: [email protected] > Subject: Characterizing a screen room > > My company is planning to purchase a screen room for radiated >emissions > precompliance testing. > > I'm aware that reflections can cause resonances and drastically >influence > readings. What kind of testing could I do to characterize the room >(aside from > simple experience)? > > -- > Patrick Lawler > [email protected] > > --------- > This message is coming from the emc-pstc discussion list. > To cancel your subscription, send mail to [email protected] > with the single line: "unsubscribe emc-pstc" (without the > quotes). For help, send mail to [email protected], > [email protected], [email protected], or > [email protected] (the list administrators). > >--------- >This message is coming from the emc-pstc discussion list. >To cancel your subscription, send mail to [email protected] >with the single line: "unsubscribe emc-pstc" (without the >quotes). For help, send mail to [email protected], >[email protected], [email protected], or >[email protected] (the list administrators). > -- Patrick Lawler [email protected] --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to [email protected] with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to [email protected], [email protected], [email protected], or [email protected] (the list administrators).
