[Elecraft] Re:Alligators and Bats

[Ron D' Eau Claire]

Ed, W5EJ, wrote:

> *My* (ARRL) Antenna book says the gain of a real-world dipole is 2.14dB
> below an isotropic source.  I don't recall any discussions about
> dipoles in
> free space, so can't comment on your 8 and ~6dB figures.  But all of the
> gain figures I remember seeing were either based on an isotropic source,
> which can raise unrealistic expectations among amateurs, or a real-world
> dipole.

Gee. Which Antenna book do you have Ed?

My ARRL Handbook ('99) shows (on page 20.3) a predicted gain for a dipole
1/2 wave above "average" ground (5 mS/m conductivity) having a gain of 7.5
dbi at an elevation angle of 26 degrees. By comparison, a vertical over the
same ground has just 0 dbi "gain" - more than 7 db below the dipole in any
terms. The angle of maximum radiation of the vertical is the same too - just
on 25 degrees - thanks to the attenuation of the lower angles by the lossy
earth.

Put the vertical over sea water and it is better - only about 1 db below a
dipole at 1/2 wavelength over 'average ground'. Of course, a dipole over sea
water has better gain from lower ground losses too.

That's consistent with my ARRL Antenna books among other references, and
with the models I have done using EZNEC of both vertical and horizontal
antennas.

In general, the vertical will do a better job at low angles (about 20
degrees) if the horizontal can't be raised at least 3/8 of a wavelength
above the ground. Of course, a low horizontal antenna will act as a cloud
warmer providing a lot more high angle radiation for close-in 'skip' than
the vertical under any conditions.

No slings or arrows, Ed, just a lot of various references that say the
dipole is better for DX unless you can't get it up in the air.

Of course a vertical will beat a horizontal antenna where you don't have
room to get at least 1/4 wave of "flat top" up in the air or you are only
interested in DX.

So I am genuinely interested in the contrary information you have uncovered!

Ron AC7AC
K2 # 1289