.....to put things straight:
isotropic antenna has 0dB gain by definition and is called 0dBi (dB
over isotropic)
quarter wave vertical over ground plane has 0.13 dBi gain.
a dipole IN FREE SPACE!!!! has a gain of 2.15 dBi.
a 5 eights wavelength vertical has a gain of 3 dBi.
this is holy writ!
so now you have them set up in correct order.
just add the lower gain from the higher one to get the difference.



Spajky wrote:
Hi guys,
hope that someone will clarify me certain doubts!

The problem: I have 2 different sources (some book, something DL-ed
from net) stating that approx.:

-isotrophic antenna (teorethical all around ball space HF radiation of
a single round point) has only 2,15dB less gain than half wave di-pole
(=2nd source)

- the book instead says that 1/4 lambda antenna has -3dB worse gain
that same dipole as before, [5/8 one just -1dB] & so my thought is,
that 1/4 antenna must be better than isotrophic one, since even if it
radiates 360° horizontally (if vertical polarized-mounted); vertically
it does not more than 120° both sides (all around).

I believe that on second source there is a mistake & was ment
that isotropic is 2 dB worse than 1/4 antenna & not 1/2 dipole.

so, it would be so IMHO : 0dB isotropic one
+2dBi 1/4 one
+5dBi 1/2 dipole (3dB more than 1/4 one)
Am I write or wrong?
--
Seasons Greetings & Regards , SPAJKY ®
mail addr. @ my site @ http://www.spajky.vze.com
more than 3y - "Tualatin OC-ed / BX-Slot1 / inaudible setup!"