Paolo, I’m going to go on some assumptions here that you are familiar with the measurement setup and process in Part 15 and ANSI C63.4:2014. If you look in section 8.2.4 there is a discussion on antenna beamwidth
You need to keep the antennas within their 3 dB of radiation or reception also known as its half power beamwidth. This typically does not come into play from 30 MHz to 1 GHz since most if not all standard EMC antennas are very wideband receivers in multiple directions. Although you should look at the datasheets of your measurement antennas to be sure. Where this does come into play (mainly) is above 1 GHz. You will find when you study the datasheets of various antennas used above 1 GHz, that their reception gets narrow. Let’s take for example the EMCO / ETS Lindgren 3115 antenna and there are many other similar antennas from ARA, Com-Power, etc. that follow this design which ironically was only designed for usage from 1 to 12 GHz. Here is a copy of the 3115’s ½ power beamwidth, you will observe that it has good E plane reception until about 14 GHz, and then drops of significantly from 15.5 to 17.5 GHz to 15 degrees or so. By doing some math you can figure out at a given measurement distance (say 3 meters) that a 15 degree half power beamwidth will only stay in the antennas reception area at some given height above the floor. You have a product on an 80 cm table, and then you are raising and lowering the antenna from 1 to 4 meters. At some point up the mast you are going to get out of the receiving beamwidth of the antenna and technically won’t be measuring any signals from the product at a given distance. [cid:[email protected]] This is really what became termed as bore-sighting although I believe that language has been removed from the standards at this point, as staying within the cone of reception or ½ power beamwidth is a much more accurate description of what needs to be done. An antenna mast that supports bore-sighting will fulfill the requirements as it will “point” the antenna towards an 80 cm high turntable at a 3 meter distance so it is within its ½ power beamwidth at all times as it travels up and down the antenna mast. Larry K. Stillings Compliance Worldwide, Inc. Test Locally, Sell Globally and Launch Your Products Around the World! FCC - Wireless - Telecom - CE Marking - International Approvals - Product Safety 357 Main Street Sandown, NH 03873 (603) 887 3903 Fax 887-6445 complianceworldwide.com<https://complianceworldwide.com/> Follow us on social media [cid:[email protected]] linkedin.com/company/compliance-worldwide-inc [cid:[email protected]] twitter.com/complianceww Privileged/Confidential Information may be contained in this message. If you are not the addressee indicated in this message (or responsible for delivery of the message to such person), you may not copy or deliver this message to anyone. In such case, you should destroy this message and kindly notify the sender by reply email. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of my firm shall be understood as neither given nor endorsed by it. From: Paolo Roncone Sent: Wednesday, March 29, 2023 1:06 PM To: [email protected] Subject: [PSES] Antenna tilting or boresigjting for radiated emissions Hi all, Is there an FCC / ANSI requirement, or maybe just recommendation, for antenna tilting or boresighting wrt radiated emissions in a semi-anechoic chamber ? If yes, can you please get me the reference section in FCC Part15 or ANSI std or somewhere else? Thanks a lot in advance! Paolo - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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