I've been away today and just discovered several postings I'd like to
comment on. I'll be in and out for the next couple of days, so won't be
able to carry on a very immediate conversation. I'll comment on this one
first.

The attenuation characteristics I've been talking about (attenuation of
primarily the low angle signal) isn't affected substantially by normal
ground systems. It's due to reflection from the ground well beyond the
boundary of typical radial wires. Increasing the number of radials will
improve the efficiency, which increases the size (actually, strength) of
the resulting pattern but not its shape. The ground reflection
phenomenon alters the shape, and this shape modification is a strong
function of the ground constants and frequency. Nothing you do with a
ground system of normal diameter will bring back that low angle
radiation. You need to move to the beach or go maritime mobile to get it.

When you model using a MININEC-based program or use EZNEC's MININEC-type
ground, you're seeing only the pattern modification due to ground
reflection. The ground system loss (that is, I^2 * R loss for currents
returning to the feedpoint via the ground) for that ground type is zero,
unless you intentionally insert a resistive load at the base of the
antenna to simulate ground system loss.

Roy Lewallen, W7EL

Cecil Moore wrote:
Richard Fry wrote:

According to the empirical results of AM broadcast radiators, and also
Roy Lewallen's EZNEC numbers in his last post in this thread, the
ground plane itself doesn't need to be perfect, or maybe salt water to
realize the gain improvement.


Point is, it has to be near perfect. 4 buried radials just
won't hack it.