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## Re: [Antennaware] Testing the theory..

 To: Re: [Antennaware] Testing the theory.. "K9AY" Thu, 29 Mar 2007 11:02:01 -0500
 ```>> ...snip... In addition I want to measure the field >> strength with the different ground system components as well. (also >> using the LP-100). My question is how far away from the antenna should >> I measure the field strength? > > > I recall reading somewhere that you should be at least 10 wavelengths > distant from the antenna. This is to ensure you are out of the near > field when taking the measurement. > > I've always wondered however, if the near field wouldn't also show a > similar change in field measurements as the far field. > > Erik n0ew Ultimately, the far field is where it is impossible to distinguish the radiation due to distribution of current along the antenna from that of a point source. This can be quite different for various antennas and arrays, which is why we have rules-of-thumb instead of definite formulae. In the near-field, A/B comparison measurements on a simple antenna like a vertical would normally be valid, but not necessarily so with changes to the ground system. The change in the surface wave (ground wave) can be different from the change in skywave. However, as long as the area of the radial system is the same (e.g. same diameter, but adding more radials), I can't think of a case where an improvement in ground wave does not have a corresponding improvement in skywave radiation. It just might be a different amount. Gary K9AY _______________________________________________ Antennaware mailing list Antennaware@contesting.com http://lists.contesting.com/mailman/listinfo/antennaware ```
 Current Thread [Antennaware] Testing the theory.., David Gould Re: [Antennaware] Testing the theory.., K9AY Re: [Antennaware] Testing the theory.., erik Re: [Antennaware] Testing the theory.., K9AY <= Re: [Antennaware] Testing the theory.., Guy Olinger, K2AV Re: [Antennaware] Testing the theory.., Ed Re: [Antennaware] Testing the theory.., K9AY Re: [Antennaware] Testing the theory.., Guy Olinger, K2AV Re: [Antennaware] Testing the theory.., Andrew Ingraham Re: [Antennaware] Testing the theory.., Bob Nielsen