A good fraction of your power is lost to the ground even if you have a
perfectly lossless ground system. To find the amount, use EZNEC (the
demo program is perfectly adequate), select MININEC-type ground and
appropriate ground constants. Set the plot type to 3D and run a pattern
calculation. The "Average Gain" reported at the bottom of the main
window is the loss due to ground reflection. Short of making a ground
screen several wavelengths in diameter, all you can do to improve this
is to move to a location where the ground is more conductive.

For example, the example file Vert1.ez shows a loss of over 5 dB in the
total radiated signal.

Ground reflection loss applys to horizontal antennas, too. But with
horizontal antennas it primarily attenuates the very high angle
radiation, while with verticals it gets the low angle radiation. You can
easily see its effect by superimposing a plot calculated with perfect
ground over a plot calculated with MININEC-type (if there's a direct
ground connection) or Real, High Accuracy(*) (if there isn't) ground.

(*) For NEC-2 users, this is EZNEC-speak for Sommerfeld ground.
Reflection coefficient ground doesn't provide any real advantage with
modern computers, so it's no longer an option in EZNEC. In v. 3.0 and
earlier versions it was called "Real, Fast Analysis" ground.

Roy Lewallen, W7EL

Cecil Moore wrote:
Richard Fry wrote:

* the peak "free space" gain of the monopole and its image is increas-
ed 3dB, because all radiation from it is confined to one hemisphere
(above the ground).


Remember, that's for perfect ground only (and maybe salt
water ground). If one buries half of a dipole in earth
ground, one loses most of that 3 dB to the ground.

For instance, EZNEC reports: The max gain of a 40m 1/4WL
vertical with 8 horizontal radials one foot above average
ground is -0.29 dBi. Raising the radials to one wavelength
above ground increases the max gain to +3.23 dBi. (Of course,
the 3D radiation patterns are not exactly the same but the
correlation to that 3 dB of image power is in there because
of decreased ground losses at increased height.)

Problem: Most everyone with a 1/4WL vertical and four buried
radials is throwing away about half of his/her source power.
Solution: Put up a horizontal dipole. :-)