Hello all, We have used Bilog antennas for NSA at 3 and 10 meters using geometry specific antenna factors for both distances, I had difficulty getting VCCI to accept the data. Care must be taken where the delta Af/MHz is big (30 to 100 MHz) to insure there is no frequency difference between the calibration sites equipment and site being tested equipment. This problem can be resolved if a Network Analyzer vs Spectrum analyzer and Tracking generator are used. regards, Ken
_____ From: [email protected] [mailto:[email protected]] On Behalf Of Peters, Michael Sent: Wednesday, October 11, 2006 8:00 AM To: Grace Lin; [email protected] Subject: RE: Antennas for Volumetric Site Attenuation Measurement Grace, The difficulty with using biconolog antennas is their large size. They tend to interfere with each other at close distances. It is unlikely that you will be able to meet site attenuation requirements below 100 MHz for a 3 meter test distance. If you are only performing 10 meter test distance measurements you may be okay. It sounds that you are having the installer calibrate the site, chances are they are probably using the most efficient method of calibration. See what antennas they use. ANSI C63.4 does not disallow the use of these antennas. I cannot speak for whether or not regulatory bodies do not approve. I would recommend the purchase of two sets of dipole antennas to perform discrete measurements at frequencies that do not meet NSA when using broadband antennas (I believe these are much less expensive than broadband antennas). This may look awkward when filing your site if you plan to use swept frequency for the rest of the measurements. Explaining the reason should get you through the filing process. If the chamber is meant for daily use, a second broadband antenna seems like a justifiable investment. If you are buying several items from the same vendor, they may give you a discount that will offset the cost. If you have not already bought your first antenna look at different vendors, some biconologs are smaller than others. Site attenuation works much better with identical antennas. If you are buying them pre-calibrated, make sure their calibration is accredited/traceable and that you will get the calibration factors you will need for NSA. Otherwise, buy uncalibrated and have an antenna calibration lab perform the measurements. General rules of thumb when performing site attenuation: Use attenuators at the balun of each antenna (smaller the better) to match impedance. Use some sort of pole (not metal) to have the antenna cable extend away from the antenna parallel to the ground plan for at least a few feet. Have your antennas calibrated with the best measurement uncertainty you can find. Having accurate antenna calibration factors for each antenna is crucial. Good Luck! Michael Peters _____ From: [email protected] [mailto:[email protected]] On Behalf Of Grace Lin Sent: Wednesday, October 11, 2006 9:19 AM To: [email protected] Subject: Antennas for Volumetric Site Attenuation Measurement Dear Members, Does anyone have a successful experience in volumetric site attenuation (per ANSI C63.4, etc.) by using a pair of bilog hybrid antennas (30MHz to 2 or 3 GHz)? A VIP from VCCI told me that I would be challenged by using a pair of bilog hybrid antennas to perform volumetric site attenuation. For daily radiated emission measurement, bilog antenna are popular, especially using automation software for initial scan. For a manufacturer, it is hard to justify a pair of biconical (30MHz-300MHz) and log periodic (300MHz-1GHz) antennas just for site attenuation measurement, used once every three years (per FCC and Industry Canada). I did some research. There is a paper to address the measurement uncertainty of the bilog antennas, titled: "Understanding the measurement uncertainties of the bicon/log hybrid antenna" ( <http: /www.ets-lindgren.com/manuals/Chen_Bilog.pdf> http://www.ets-lindgren.com/manuals/Chen_Bilog.pdf) written by Zhong Chen of ETS-Lindgren. I spoke to the author. He told me when using bilog antennas, if the results do not meet 4 dB requirement, it might not mean the site was not good as the measurement uncertainty might cause the incorrect results. I am suggested to try to use a pair of bilog hybrid antennas to perform volumetric site attenuation after a chamber manufacturer completing its measurement and compare the results. The problem is: I am not sure if I can convince my manager to rent a bilog antenna to try it. I only plan to purchase one bilog antenna if it cannot be used for site attenuation measurement. I figure out it may be a good idea to ask for your experience. I appreciate your input. Best regards, Grace Lin Crestron Electronics, Inc. 6 Volvo Drive Rockleigh, NJ 07647 <http://www.crestron.com/> www.crestron.com - ---------------------------------------------------------------- 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 **************************************************************** The information transmitted in this message is confidential and may be privileged. Any review, retransmission, dissemination, or other use of this information by persons or entities other than the intended recipient is prohibited. If you are not the intended recipient, please notify Analogic Corporation immediately - by replying to this message or by sending an email to [email protected] - and destroy all copies of this information, including any attachments, without reading or disclosing them. Thank you. - ---------------------------------------------------------------- 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 email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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
