[600MRG] ERP, EIRP, How & Why

[Edward R Cole]

Ken,

Then all we can do is agree to disagree.  You are talking about power 
gain and loss and calling it antenna gain.  As I already cited (Dr. 
John D Kraus - author of "Antennas" and accepted authority defines 
antenna gain = directivity).

I can agree that antenna modeling is only approximate and will have 
disagreement between different models.  But most hams do not have the 
instrumentation to do actual field strength measurements and rely on 
models.  I cited mine with my measurements so you know how I arrived 
at the Impedance and gain figures.

Many antenna sw include ground loss into their "gain" calculations so 
the whole subject of gain is muddled.
Directivity of an isotropic radiator = 1 (0 dBi) thus it cannot be 
negative else it is non-radiating (ergo dummy load).  Your gain 
figures incorporate ground losses and radiation efficiency - thus we 
agree to disagree.

My calculations were taken from Fritz's guidelines (best as I could 
understand them).

I would like to see the spreadsheet that was developed to compare with my math.

As far as real ERP - I have no way to measure it (real variables are 
much too complicated for mathematical computations  - thus we use 
simplifying models).  Probably beat this topic to death? ;-)

73, Ed

At 09:24 AM 1/28/2015, Kenneth G. Gordon wrote:
>On 28 Jan 2015 at 8:57, Edward R Cole wrote:
>
> > Ken,
> >
> > Don't confuse antenna efficiency with gain.
>
>I'm not.
>
> >  Kraus (Antennas) defines
> > antenna gain as directivity.
>
>Of course: no antenna can output more total RF than is impressed on it. One
>can only "point" more or less of that RF in some particular direction or
>directions, and less of it in others. This is what we call 
>"gain"...which it really
>isn't. "Gain" with regard to antennas is certainly a handy word to describe
>what is actually happening, but many (most?) hams misunderstand what is
>actually taking place.
>
> >  The inverted-L radiates less upward
> > than horizontally (as most vertical antennas do), thus a mild bit of
> > directivity.  Rudy shows nearly the same amount in his calculations
> > (1.7 dB).  But coupled with 4.6% efficiency it will not radiate
> > anywhere near a full-size quarter wave vertical.  This gain was
> > derived from EZNec.
>
>Well, EZNec is a handy tool (as is MMANA GAL, which I use) but it most
>certainly is only an approximation at best. It is a model. Those programs can
>give us a good idea of what is happening, but none can exactly describe
>what is actually taking place, either.
>
> > How did you arrive at your -2 dB gain?  At what frequency?
>
>The antenna was designed specifically for 80 and 40 meters. At 80 meters, it
>shows a "gain" of MINUS approximately 2 dB over a resonant dipole
>according to every reference I could find on the subject.
>
>I am also using a version of VOACAP. In that collection of programs, one of
>those is a way to input your own personal antenna parameters to the main
>program in order for it to provide more accurate point-to-point propagation
>data.
>
>THAT also shows my antenna as having approximately MINUS 2dB "gain"
>over a dipole. The actual figure, as I remember it,. is very close to 1.87
>dB...minus.
>
>Lastly, my experience with the antenna over the past 10 years pretty much
>bears this out.
>
>Ken W7EKB
>
>_______________________________________________
>600MRG mailing list
>600MRG at w7ekb.com
>http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     dubususa at gmail.com