With respect, the "industry standard" Isotropic reference definition
*doesn't* change in the presence of ground - it remains at a power
density of Pt/(4*Pi*r^2) in all cases.
It may be that leads to some "condrums" for you, but they follow from
the definition - it's not an error in EZNEC, which is simply applying
the standard interpretation.
For me there is no conundrum. If I model a quarter-wave vertical over
perfect ground I see a maximum Gain of 5.15dBi - the 2.15dBi I would
expect due to the elevation pattern (same as a half-wave dipole), and
3dB because all of the transmitted power is now constrained to one
hemisphere rather than the two hemispheres "occupied" by the reference
Isotropic source. I see no problem there.
On 08/01/2011 20:13, Dr. Gerald N. Johnson wrote:
> What I see is that the changes in isotropic reference definition in the
> presence of a ground cause the program to show greater gain numbers that
> make the casual user conclude that there is a gain caused by the
> presence of the earth that is not there when signal strength in the main
> lobe is measured compared to that antenna in free space.
> 73, Jerry, K0CQ
> On 1/8/2011 6:48 AM, Steve Hunt wrote:
>> I can understand that the interpretation of dBi which appears in most
>> engineering texts (and possibly the IEEE definition?) throws up
>> conundrums with which you are uncomfortable. But what I think is unfair
>> is to claim that EZNEC is in error, simply because it adopts the
>> "industry standard" interpretation rather than an alternative that you
>> might prefer.
>> I make widespread use of EZNEC, and when I saw someone as authoritative
>> as yourself state that it is 3dB in error I felt it needed further
>> Steve G3TXQ
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