The reason for height-scanning is that there are unavoidable reflections from the groundplane, and the only way to ensure that your measurement geometry is not causing a deep null is to scan the height. The reason that reflections are unavoidable is that at 30MHz, absorber would have to be 2.5m deep which is not practical or economic.k
At frequencies above 1 GHz, absorber is practical and economic, and I is easy to put absorber on the ground to minimise the small effect that there might be on your measurement due to ground reflections, and not bother with height scanning. Luke Turnbull >>> "Wiz" <wizbc...@charter.net> 12/02/2004 15:36:41 >>> Hello, I have a need to make radiated measurements up to 40 GHz. I uses a low loss cable that gives me enough dynamic range up to 18GHz. The cable is very short and I have to move my measurements equipment out to the antenna. I know I need to get a pre-amp and mixer, but what do I do about the cable loss? I have called many places and I cannot find good enough cable to measure to 40 GHz. The other alternative is waveguides as I understand. Those would, I assume, be coupled directly to the input of the mixer. This does not allow for antenna height adjustments form 1 to 4m as required. I have seen other test reports where high frequency data was taken where the antenna was held at about 1meter. I can understand this since emissions will likely be very directional at those frequencies. Is it acceptable to make measurements with the receive antenna at 1 meter only? Thanks for any information you can provide. Wiz This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: emc_p...@symbol.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
