Dave,
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
non-starter.
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.
73,
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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