Doug, You need a low permittivity (<2), low loss tangent material.
The microwave oven test provides approximate information about the magnitude of the loss tangent, but only for one frequency. The permittivity has impact on the field homogeneity, especially when the EUT is significantly smaller than the surface of the table. Try to imagine the field. With the resin used in these composite materials, you end up with a black box, so some testing of the purchased material is required. Just my 2c. Best regards Michael Nagel Michael Nagel Senior Staff EMC Engineer Embedded Computing Emerson Network Power T +49-89-9608-0 F +49-89-9608-2376 [email protected] www.emersonnetworkpower.com/embeddedcomputing Emerson Network Power - Embedded Computing GmbH, Lilienthalstr. 15, D-85579 Neubiberg/Landkreis München, Deutschland / Germany. Geschäftsführer Josef Wenzl, Amtsgericht München HRB 171431, VAT/USt.-ID: DE 127472241 From: [email protected] [mailto:[email protected]] On Behalf Of Scott B. Lacey Sent: Dienstag, 8. Juli 2008 15:19 To: Powell, Doug Cc: [email protected] Subject: Re: Composite materials for > 1 GHz testing Doug, The installation instructions for most of these materials specify an extra wide gap on deck boards due to moisture expansion. Most of these materials contain sawdust as well as recycled plastic. There are some truly waterproof materials used in the marine industry and available as sheet goods. Whatever material you use should be tested by placing a piece in a microwave, along with a container of water (to protect the microwave). If the material gets warm it should not be used with RF. This is an old radio experimenter's trick for testing improvised coil forms. Another thought: There are many plastic resin tables available for outdoor use. If you bought a small snack table and sawed a piece off you could test it in the microwave. If ok, go back and buy the larger table from the same manufacturer. The problem with using plastics for RF usage is that many of them contain fillers that may cause a problem. Scott B. Lacey On 7 Jul 2008 at 16:06, Powell, Doug wrote: > > I have an out of the weather application want to build non-conductive > tables. The testing will be for radiated immunity and emissions above 1 GHz. > > I know about the IEEE paper for 2001 and it has some good suggestions > (polystyrene) and I found some more recent information in the EMC-PSTC > archives. > > I would like to know if anyone has had experience with composite > lumber commonly available in local hardware stores and lumber yards. > For example: http://www.correctdeck.com/products/dcl/ > > Any good or bad experiences? > > > > > > -doug > > Douglas E. Powell > Engineering Manager > Corporate Product Compliance > Advanced Energy Industries, Inc. > > > > This message, including any attachments, may contain information that > is confidential and proprietary information of Advanced Energy > Industries, Inc. The dissemination, distribution, use or copying of > this message or any of its attachments is strictly prohibited without the > express written consent of Advanced Energy Industries, Inc. > - ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society > emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a > message to the list, send your e-mail to [email protected] > Instructions: http://listserv.ieee.org/request/user-guide.html > List rules: http://www.ieee-pses.org/listrules.html > For help, send mail to the list administrators: > Scott Douglas [email protected] Mike Cantwell [email protected] For > policy questions, send mail to: > Jim Bacher: [email protected] David Heald: [email protected] All > emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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