On Sun, 03 Apr 2005 17:15:03 -0500, Cecil Moore
wrote:

Buck wrote:
What is the gain of a dipole over an imaginary isotropic antenna? I
believe I read 7.x somewhere. Whatever it was, it was greater than
anything I expected.

In *free space* the gain of a dipole over isotropic is about 2.14 dB.
Over ground, the reflections from the ground add another few dB.
dBi is *always* referenced to free space. An isotropic over perfect
ground would probably have a gain of about 3 dBi assuming no destructive
interference. A dipole over perfect ground has a gain of about 7.5 dBi.
Rule of thumb: A dipole over average ground has a gain of about 6 dBi.


I was trying to calculate the ERP of his HT into a vertical dipole and
accounting for the loss of RG-58A coax of 25 feet. It seemed his ERP
was outrageous compared to what I would have expected. I calculated
it with the gain of the dipole over an isotropic as referenced in the
ARRL handbook. The only figure in there was the 7.5 dBi gain.

I saw a harendous (sp) number for his ERP so I decided to stop the
explanation until I could confirm this. I figured I was doing
something wrong.

His HT is about 5 watts output.

Thanks
Buck
--
73 for now
Buck
N4PGW