Hello all,
I think that the "ground gain" and the "ground losses" depends on two different
phenomena. Ground gain should come from reflections from ground at a distant point
(far field) from the source combining with the direct ray from the same source with
the proper phase. The type of antenna used shouldn't matter since it will be seen
as a point source at a large distance; of course the polarization w.r.t. ground
will be important.
The ground losses depend on the presence of dissipative materials near the antenna
(near field); for a small electric dipole the electric field near the antenna
should be more intense than for a small magnetic loop. On the other hand, the
magnetic field near a loop antenna should be higher than for an dipole. At a
distance (far field) there is no difference between the two (for the same radiated
power, of course). So probably for a monopole it is important to have a dielectric
with low losses (and ground usually is not), while for a loop a lossy dielectric
near the antenna has less effect, due to the weaker electric field. But I have no
idea how lossy is the ground as a magnetic material...
73 de Claudio, IN3OTD
Rik wrote:
And to make things more complex, what about a loop close to a
not-so-perfect ground plane ?
Either the loop is not (or little affected) by the ground. That means
little or no groundloss (as is claimed by some) but at the same time it
would mean that the loop will also not benefit from any "ground gain".
On the other hand, if the loop benifits form significantly from
"groundgain" then I would expect that the loop would also suffer from the
groundlosses, as a vertical monopole does.
Any clues ?
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