Richard, Regarding the non uniformities (rippling) on the ground mesh, the detailed equation is given in the ANSI C63. Manual (at the back) dealing with Site Attenuation, this manual tends more towards the optical Rayleigh Criterion. I do not think that this will be a problem at frequencies such as 30MHz (10 metre wavelength; take lambda/10 = 1 metre (CISPR 11 clause 8.1); Site imperfections will really show up at higher frequencies.
If the NSA improves at 10 metres, it points more to Mutual Impedance effects. Your list couldn't be more comprehensive, I intend to stick it on our hut at the OATS; the only thing I can add is temperature stability and a calm day, so that between the Vdirect and V antenna measurement at a particular frequency you don't see 4 seasons. Other factors could be antenna impedance and VSWR changes with height; Balun VSWR and losses (deterioration) And really, at the end of the day, just because the site attenuation of any site is accurate, this does not mean that the measurement uncertainity has come down or that the EMC tests that are carried out on the site are equally accurate (nothing to do with the lab or personnel!!) . Regards Arun Kaore EMC Engineer ADI Limited Systems Group Test & Evaluation Centre Forrester Road, St Marys NSW 2760 P O Box: 315, St Marys NSW 1790 Tel: 61 2 9673 8375 Fax: 61 2 9673 8321 Email: kao...@sg.adi-limited.com.au <mailto:kao...@sg.adi-limited.com.au> -----Original Message----- From: WOODS, RICHARD [SMTP:wo...@sensormatic.com] <mailto:[SMTP:wo...@sensormatic.com]> Sent: Friday, 23 July, 1999 1:51 To: 'emc-pstc' Subject: Root Causes of NSA non-compliance I can think of the following items that must be investigated if an OATS is not vertically NSA compliant. Can you think of others? Antennas and Cables * Antenna factors * Balance * Currents on transmit cable * Cable proximity to antenna * Dipole length * Bent elements * Mutual coupling factors (at 3m only) * Antenna spacing * Antenna height * Antenna variation from vertical orientation Receiver with tracking generator * Calibration * Internal attenuator & scale tolerance * Drift Pad * Size of ground screen * Bonding of screen seams * Earthing of screen around edges * Flatness * RF conductivity from table to screen * Height above surrounding terrain Site * Reflecting objects within ellipse * Reflecting objects outside ellipse * Conductivity of surrounding earth Human Factors * Procedure * Readings * Calculations --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org <mailto:majord...@ieee.org> with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com <mailto:ed.pr...@cubic.com> , jim_bac...@monarch.com <mailto:jim_bac...@monarch.com> , ri...@sdd.hp.com <mailto:ri...@sdd.hp.com> , or roger.volgst...@compaq.com <mailto:roger.volgst...@compaq.com> (the list administrators). --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
