Right. But still reduces the screening of your chamber from 100 dB or so to 30...40 and thus may cause problems with immunity testing.
That brings me to a related subject: The risks that go with RF energy leaking out. Well if you are in the middle of Texas, that may not be such a problem. But my chamber is located precisely below the landing path of Rotterdam airport, and civil aircrafts like B737 fly approx. 150m (500ft) above it. Any idea what may happen, if a substantial amount of the right frequency leaks out at the right (?!?) moment ? Well, in fact I don't know. Is there someone on this list with pertinent data on this subject ?? Someone that can provide risk frequencies ? Gert Gremmen Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Michael Heckrotte Verzonden: donderdag 15 januari 2009 3:26 Aan: Frank Krozel; emc-p...@ieee.org; emc-pstc@LISTSERV.IEEE.ORG Onderwerp: RE: Anechoic Chamber: Pass-through on hydraulic lines All, As was stated some months or years ago on this list regarding this same topic: The waveguide pipe is an outer conducter, the wire going through it is a center conductor, and the combination of insulation/air is a dielectric; this configuration is also known as a coaxial cable = transmission line. If you absolutely must feed a wire or an ungrounded coax into a chamber, and the wire or coax ground cannot be filtered, then feed the wire or coax through two absorbing clamps, one inside the chamber and one outside the chamber. Place an absorbing clamp at each end of the waveguide pipe, butted up as close as possible to the waveguide pipe. This is effective over the frequency range at which the absorbing clamps provide decent common-mode decoupling. Best Regards, Mike Michael Heckrotte Director of Engineering Compliance Certification Services 47173 Benicia Street, Fremont, CA 94538 Main: (510) 771-1000 Direct: (510) 771-1121 Fax: (510) 661-0885 michael.heckro...@ccsemc.com From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Frank Krozel Sent: Wednesday, January 14, 2009 6:25 AM To: emc-p...@ieee.org Subject: Re: Anechoic Chamber: Pass-through on hydraulic lines All, Tim's comment made me think. In the past, I have seen hydraulic lines passed through waveguide feed-thrus that have re-inforced metal braid. Be aware of this if you need to pass hydraulic lines into your chamber or RF shielded enclosure. Alternatives do exist that are non-conductive. Regards Frank Krozel http://www.electronicinstrument.com From: Haynes, Tim (SELEX GALILEO, UK) To: emc-p...@ieee.org Sent: Wednesday, January 14, 2009 6:26 AM Subject: RE: Anechoic Chamber: Pass-through vs. Bulkhead Hi All, Conventional wisdom is, as stated, to bond the shield of a cable, hydraulic pipe, or any other electrically conductive - non-energised item that penetrates the shield wall. This is usually done with a purpose made "bulkhead" connector and is, again, usually done at a purpose made access plate in the shield room wall. Energised items cannot be connected to the shield and here the conventional wisdom is to connect the energised conductor via a filter that has its local ground connected to the shield wall. However, it might be acceptable to use a pass-through pipe where the pipe is long and can provide a sufficiently high capacitance to ground to form a functional filter at the frequencies of concern. The capacitance might be increased by "stuffing" the pass through pipe with conductive wire wool. I once had no option but to "pass through" a cable into the chamber. The project allowed me to remove the outer insulation at the pass through and I bonded the cable shield to the screened room by using a bolt to apply pressure to a shim of metal that held the cable firmly to the metal of the pass through pipe. That worked well. I hope the information helps. Regards Tim ************************ Tim Haynes A1N10 Electromagnetic Engineering Specialist SELEX Sensors and Airborne Systems 300 Capability Green Luton LU1 3PG ( Tel : +44 (0)1582 886239 7 Fax : +44 (0)1582 795863 ) Mob : +44 (0)7703 559 310 * E-mail : tim.hay...@selexgalileo.com P Please consider the environment before printing this email. There are 10 types of people in the world-those who understand binary and those who don't. J. 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