Manfred,
On 5/23/2017 2:21 PM, Manfred Mornhinweg wrote:
Stop for a moment. An end-fed antenna, and a battery-powered
oscillator? Where did the other pole go??? You surely know as well as
I do that current flows betwen two poles. An end-fed antenna is
usually fed against ground, or against a counterpoise. The entire
antenna system comprises the antenna, the ground or counterpoise, all
wiring between them, and any other nearby conductors coupling to the
system by capacitance, mutual inductance, or both. We need to find out
how all the house interacted with your oscillator and antenna, when
you made that test!
And even if your end fed antenna had been radiating a purely
horizontal signal, placing your receiving loop higher or lower at an
azimuth angle aligned with the antenna would produce a vertically
polarized signal at the receiving antenna.
I was mistaken about the transmitter antenna. I double checked that
experiment documentation, and the antenna was a short, horizontal dipole.
Stop for another moment! A loop antenna held in a vertical plane has a
horizontal magnetic axis. So its polarization is vertical when seen
from the side, and horizontal when seen from above or below. And
mixed/slanted when seen from another angle. The directivity is such
that looking through the loop, along the magnetic axis, is a null.
Maximum reception is equally from the sides, from above and from
below. If you point the magnetic axis of the loop at the signal
source, in theory you should receive nothing. Anything you do receive
is by reflections, and the loop responds to vertically polarized
signals bouncing in from the side walls or vertical objects, and
horizontally polarized signals bouncing in from ceiling, floor and
horizontal objects.
And all of this is true only if the wavelength is short enough!
Direction-finding HF signals inside a building, and testing their
polarization, is pretty hopeless, because the wave is typically longer
than the free spaces, and you get a very complex mess of local
electric and magnetic fields rather than a well developed, well
defined wave!
The tuned loop was held such that the feed point of the loop was at the
bottom. When holding the loop with the support pole perpendicular to
the ground, vertical polarized signals were nulled when looking through
the loop and maximized when the loop was rotated 90 degrees. This was
determined by using an oscillator with a short transmitting dipole
antenna and orienting the transmitting antenna both vertically and
horizontally. I then excited the house wiring by coupling a signal
generator into the house wiring with a capacitor. It was clear that the
signal was always nulled when I looked through the loop as described
above. I have concluded from this exercise that local RFI generated
inside a house is always vertically polarized. Using this method, I
could easily locate my house, and have located about a dozen other
houses with either grow light ballasts or switch mode power supplies.
I just don't understand why the vertical polarization is predominate
until you get to about 3 meters from the house.
I apologize for this subject on the amp reflector. If there are other
comments, I will take it off the reflector.
73, Tom W0IVJ
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