[600MRG] ERP, EIRP, How & Why

[Edward R Cole]

Ken,

Don't confuse antenna efficiency with gain.  Kraus (Antennas) defines 
antenna gain as directivity.  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.

How did you arrive at your -2 dB gain?  At what frequency?

73, Ed - KL7UW

At 08:29 AM 1/28/2015, Kenneth G. Gordon wrote:
>On 28 Jan 2015 at 8:18, Edward R Cole wrote:
>
> > Pat,
> >
> > Sounds right to me.  I determined R+jX from a model in
> > EZNec.   R=0.83 and measured R with my modified MFJ analyzer as
> > 18-ohms.  Po=100w resulted in TPR= 4.61w  EZNec indicated gain
>
>Gain? How can your antenna have any real "gain"? It is much too short to
>have any real gain. Please explain.
>
>Even my 55' vertical has a "gain" of approximately MINUS 2 dB on HF when
>tuned to resonance.
>
> > of
> > 1.48 (1.7 dBi) giving EIRP=1.48*4.61 =  6.8w.  ERP = EIRP/1.64 = 4.15w.
> >
> > Only variance with Rudy's calculation is he adds 3-dB gain for dipole
> > over perfect ground.
> >
> > My antenna is base loaded inverted-L: 43x122 feet.
>
>For a total length of 165 feet. Wavelength at 472 KHz is about 2081 feet.
>Your antenna is about 8% of that.
>
>I suggest that your actual ERP is much LESS than you have calculated. I do
>not see how it can be otherwise.
>
>Ken W7EKB
>
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73, Ed - KL7UW
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