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Re: [TenTec] NEC, ground, grounds, and radials.

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] NEC, ground, grounds, and radials.
From: Steve Hunt <steve@karinya.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sun, 09 Jan 2011 09:46:27 +0000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

Thank you for the clarification, and for confirming my points:

* dBi is always referenced to an isotropic radiator *in free space*
* EZNEC is consistent with the industry definition and is not 3dB in error

I think it was misleading of Jerry to talk about inflated gain figures 
from EZNEC. If he wants to embark on a crusade he needs to get industry 
to change the standard definition, not to get Roy to modify his 
software; but as you have noted, the concept of a "dBi" which produces 
differing power densities depending on the environment is likely a 

I understand the point you and Jerry are making, although the concept of 
"fairness" escapes me in this context. For me "dBi" is just a shorthand 
way of defining a reference power density at a particular range and 
input power level; viewed that way, there are no "conundrums" and the 
hemisphere issue doesn't arise.

Steve G3TXQ

On 09/01/2011 00:14, Dave Kelley wrote:
> Dear Steve and Jerry,
> I think I might not have been clear in my original post about the 3 dB
> gain "error" in NEC. The moment method codes like NEC, EZNEC, Mininec,
> and all of their variants are calculating gain in dBi correctly. I
> cannot access the "IEEE Standard Definitions of Terms for Antennas"
> right now, but I am sure that it states or implies that gain measured
> in dBi is always referenced to an isotropic radiator in free space
> whether the antenna being modeled is over a ground plane or not. It
> has to be this way; otherwise, it could create untold confusion. What
> I was saying in my original post (and I think Jerry agrees) is that to
> be "fair," one should compare an antenna mounted over ground to an
> isotropic radiator radiating into a half-space (a "hemi-isotropic"
> radiator?). However, there is no standard gain unit defined this way.
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