[Amps] new amp race (RFI polarization)

[Tom Thompson]

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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