If it's mutual coupling... sure. But if it's a surface wave, that's real field strength. If the reason for 3 meters -- an approximation of distance to the victim receiver in a residential area -- is to be preserved, then perhaps this is a non-issue, as the error is all on the high side, and emissions will be reduced even lower than they would be on a ten meter site.
(As an aside, can anyone here say if the COmmission has ever specifically ruled on how far away from residences Class A equipment must be kept? I remember a few years ago some chap got a NAL for operating a graphics work station in his home... but what about separate buildings out back, etc. ?) Cortland ====================== Original Message Follows ==================== >> Date: 25-Aug-97 07:21:19 MsgID: 1054-2813 ToID: 72146,373 From: "Grasso, Charles (Chaz)" >INTERNET:gra...@louisville.stortek.com Subj: RE: Antenna Calibration/Site Attenuation Chrg: $0.00 Imp: Norm Sens: Std Receipt: No Parts: 1 Hi, Yes I attended that presentation. In ANSI C63.4 Methods for SA there is a "fudge factor" for taking out the mutual coupling between antennas for 3M SA measurements. Doesn't this take care of the problem? Charles Grasso EMC Engineer StorageTek gra...@louisville.stortek.com Tel:(303)673-2908 Fax(303)661-7115 >---------- >From: Cortland Richmond[SMTP:72146....@compuserve.com] >Sent: Saturday, August 23, 1997 1:53 PM >To: Thomas Donnelly; ieee pstc list >Subject: Re: Antenna Calibration/Site Attenuation > >Tom, > >Did you get to the presentation about getting the most out of a biconical >antenna? Some thoughts contained there on antenna calibration, too. > >I found some time ago that using antennas does lead to the kind of mutual >coupling Martin talked about, and also -- and this is not mentioned much -- >even >with small sources, there is a definite surface wave near the ground plane at >30-35 or 40 MHz. This skews reading upwards, but as it is part of the site >propagation, I think it has to be factored out by doing that vertical >antenna >factor measurement. A couple more meters, and the surface wave is no longer >a >problem. I say surface wave, because I don't think this is a mutual coupling >problem. Even small sources seem to generate it. I am presently working on an >antenna calibration for a semi-anechoic chamber in which I shall be able to >investigate this more closely. > >Regards, > >Cortland > > ====================== End of Original Message =====================
