In article , craigm
wrote:

Telamon wrote:

In article , craigm
wrote:

RHF wrote:


Usually getting the Element of the Loop Antenna at least Three
Feet above the Roof (Five Feet is better) will get the Loop out
of the Building's RFI / EMF Noise Envelop.


What technical foundation exists for this type of statement?

Most any building materials have a dielectric constant higher than
air (1) and tend to bend the electric field lines around the house.
The field lines generated inside penetrating the outside tend to
head toward earth.


Are you saying the wood, fiberglass and shingles have enough effect
to make three or five foot separation sufficient to reduce the field
from noise generated inside a house?

It is not a reduction as much as additional bending (refraction) of the
field lines to follow the contour of the house to earth so the field
strength falls off faster than it otherwise would without the
difference in dielectric constant between the building materials and
air.

There is always some dielectric heating loss to add to that but at 1 to
30 MHz it would be very small.

If noise from your neighbors house is bothering you there is a good
chance it is diminished when it rains if the noise is radiating
directly from the neighbors house because the building material
dielectric constant would be much higher than when it is dry.

Why then would anyone have trouble with noise radiated from their
neighbor's house?

Usually because the radiated noise induces currents in other nearby
conductors around like gutters, utility lines that then re-radiate the
noise.

Some of the noise is EMI through common AC mains connections.

Some of the noise generation is also RFI (far field) to begin with
instead of just near field energy.

--
Telamon
Ventura, California