[Amps] new amp race (RFI polarization)

[Tom Thompson]

I have tracked down a lot of man made RFI (mostly from grow light 
ballasts) and without exception the signal is vertically polarized until 
you get very close to the source.  I found this very interesting, so a 
friend and I used a battery powered oscillator with an end fed 
horizontal wire for an antenna.  We placed it horizontally on the floor 
of his house on the second floor, the first floor, and finally in the 
basement.  The signal was always vertically polarized on 40m until we 
got very close to the source. I was using a tuned loop antenna for 
receive.  I had previously determined that the null looking through the 
loop indicated vertical polarization, whereas the peak looking  through 
the loop indicated horizontal polarization.  I initially thought this 
was caused by the source and antenna being so low to the ground on 40m.  
Most of the radiation is going straight up, but EZNEC does not show a 
big difference between the vertical and horizontal polarization.  I 
thought this phenomenon might be caused by the direction of the house 
wiring, but that is pretty random, and the oscillator test definitely 
had a horizontal antenna that produced predominately vertical 
radiation.  Any thoughts?

Tom   W0IVJ

On 5/21/2017 8:02 PM, Manfred Mornhinweg wrote:
> Ron, and all,
>
>> I learned:  Natural noise (lightning) is vertically polarized because
>>  lightning is a vertical event.
>
> I have seen lots of horizontal lightning, from cloud to cloud, or inside
> the same cloud.
>
> Even when I have seen vertical lightning to ground, it has usually
> happened simultaneously with horizontal lightning, that brings the
> charges to the spot in the cloud where the vertical part starts.
>
> Of course even horizontal lightning noise will arrive at one's place 
> polarized horizontally, vertically, or anything in between, depending 
> on the direction of the lightning relative to the direction between 
> one's place and the lightning. Horizontal lightning aligned with your 
> path to the lightning generates vertical polarization at your place. 
> Just like a horizontal dipole antenna operates with vertical 
> polarization at the directions the wires point.
>
> And then again, any far-away lightning that you hear through 
> ionospheric propagation will anyway have its polarization thoroughly 
> mixed up.
>
>> Man made noise, like noise motor is generally polarized with it's
> > feed wiring.
>
> Yes. And that's typically more horizontal than vertical, because power 
> lines strung horizontally from pole to pole and pole to houses do much 
> of the radiating. But some vertical power wires exist - just think 
> about tall buildings - and of course the noise radiated by a 
> horizontal power line running straight away from your place appears 
> vertically polarized.
>
> In short, I don't think there is much merit to the idea that noise is 
> most commonly vertically polarized. Neither manmade nor natural noise.
>
> The real reason why vertically polarized antennas acquired a 
> reputation for being noisy is that many such vertically polarized 
> antennas are simple monopoles fed against ground. This places them at 
> ground level, where there is most manmade noise. Also most hams run 
> such antennas without a common mode choke, thinking that the 
> unbalanced antenna nicely matches the unbalanced coax cable. So if the 
> grounding is anything but perfect, the feedline becomes part of the 
> antenna system, and that feedline runs into the house and right past 
> switching power supplies, CFLs, power wiring, etc. Put the same 
> vertical antenna high up on a tower, using an artificial groundplane 
> up there, with a proper common-mode choke on the feedline, and it will 
> be as quiet as a horizontal antenna installed at the same place.
>
> Most people can easily do this test using a VHF antenna: Place it 
> vertically or horizontally, at the same height, and compare. Noise 
> stays the same. I used switchable polarity Yagis on VHF and UHF for 
> many years, operating on satellites. I could switch to vertical, 
> horizontal, left hand circular and right hand circular polarizations. 
> There was no general noise advantage in either of them. Just the 
> signals, and specific individual noise sources, got stronger or 
> weaker, depending on the polarization they had.
>
> On UHF I didn't have much manmade noise, but on VHF I did.
>
> Manfred
>
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