Is man-made noise really vertical?

Discussion in 'Amateur Radio News' started by VK6FLAB, Sep 29, 2018.

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  1. VK6FLAB

    VK6FLAB Ham Member QRZ Page

    foundations-of-amateur-radio_300.jpg
    Foundations of Amateur Radio

    Is man-made noise really vertical?

    One of the often repeated attributes of noise and antennas is that man-made noise is vertically polarised and that is why a vertical antenna sounds noisier than a horizontal dipole. It's an interesting thing to say, but it it true?

    Let's start with what constitutes man-made noise. Cars driving past, solar panel inverters, pool pumps, high-tension power lines, garage door openers, broadband internet modems, LED lights, lawn mowers, leaf blowers, plasma televisions and so on. The more you think about this, the more noise makers you discover.

    So, are these noise sources all aligned in the same way, making the same noise?

    Clearly not. There is no alignment standard for installing a lamp, how to align your lawn mower, which direction to drive, what angle to point your garage door opener, so the statement that man-made noise is vertical is clearly bogus.

    That doesn't mean that the rest of the statement is also wrong. A vertical antenna in an urban environment often sounds much noisier than a horizontal one, sometimes by several dB.

    So what's going on?

    One suggestion is that the difference lies in the antenna itself. What if both noise sources, horizontal and vertically polarised were the same, but the antenna heard them differently, how would that look?

    For starters, a horizontal dipole has a higher sensitivity at a higher angle than a vertical antenna does. So anything arriving at a low angle is picked up by the vertical, but not by the horizontal dipole.

    The noise that we're talking about is local, we'll get to why in just a moment. Being local, it gets to the antenna via ground wave propagation rather than via the ionosphere. I claimed that the man-made noise we're discussing is local. It's not all local, but if it's remote, it's coming via the ionosphere and we know that it arrives at whatever angle it pleases, so there is little or no difference between a vertical and a horizontal dipole from a noise perspective for signals arriving via the ionosphere.

    There is another effect. Attenuation or signal loss. In this case loss of strength. Specifically noise strength. More attenuation is the same as more signal loss.

    Combining ground wave propagation and attenuation brings us to another difference between a horizontal and a vertically polarised noise source. A horizontally polarised ground wave experiences more attenuation than a vertical one. This means that noise that is local travels further and is louder when it's vertical, compared to when it's horizontal, sometimes the difference is over 20 dB.

    I've been talking about horizontal and vertically polarised noise, but what if the noise is coming at an angle, like the random noise makers around you? A simple way to think of it is that every angle has a horizontal and a vertical part, in much the same way as a right-angle triangle has three sides, one horizontal, one vertical and one on an angle.

    Putting this all together, we have a number of different effects, all conspiring to make the vertically polarised part of noise travel further, be louder and received better by a vertical antenna, compared to the horizontally polarised part which doesn't travel as far, is softer and heard less by a horizontal dipole.

    One more thing. The isolation between vertical and horizontal polarisation can be as much as 40 dB, so a horizontal dipole won't hear vertically polarised signals well if at all and vice versa.

    That doesn't make the vertical antenna useless, far from it. It's great for transmitting a long distance signal, it's small, simple to set-up and if you're in a quiet area, away from noise makers, around 500m to a kilometre or so, it's just fine as an antenna. It also doesn't need to be erected half a wavelength above the ground, doesn't need any sky-hooks, is omni-directional and in common use for most local mobile communications, so don't write off the vertical, just because it sounds noisier.

    All antennas are a compromise between various elements. I've said it before and I'll say it again, likely plenty more times beyond that. The perfect antenna does not exist. We can prove that, so what ever you pick, what ever you think is the most important, that's what you'll start with and select various aspects as you go.

    A vertical antenna is no worse than a horizontal dipole, it's different. Just like a Yagi is different, or a discone, or any one of the infinite supplies of antenna options. Knowing what the parameters are is the first step.

    Oh, and if your neighbours complain about your lawn, tell them it's because of your noise-floor.

    I'm Onno VK6FLAB

    To listen to the podcast, visit the website: http://podcasts.itmaze.com.au/foundations/ and scroll to the bottom for the latest episode. You can also use your podcast tool of choice and search for my callsign, VK6FLAB.

    All podcast transcipts are collated and edited in an annual volume which you can find by searching for my callsign on your local Amazon store, or visit my author page: http://amazon.com/author/owh.

    Foundations of Amateur Radio Volume 7 is out now - with chapters on digital modes, coax connector loss, waterfalls, station performance and more.

    Feel free to get in touch directly via email: onno@itmaze.com.au, or follow on twitter: @VK6FLAB (http://twitter.com/vk6flab/)

    If you'd like to join a weekly net for new and returning amateurs, check out the details at http://ftroop.vk6.net, the net runs every week on Saturday, from 00:00 to 01:00 UTC on Echolink, IRLP, AllStar Link and 2m FM via various repeaters.
     

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    WD4IGX, K4KKQ and N0TZU like this.
  2. W1YW

    W1YW Ham Member QRZ Page

    To listen to the podcast, visit the website: http://podcasts.itmaze.com.au/foundations/ and scroll to the bottom for the latest episode. You can also use your podcast tool of choice and search for my callsign, VK6FLAB.

    ----------------------------------------

    Shouldn't this be listed as 'PODCAST'

    --NOT News'?
     
    NN4RH, VK6NSB and NU4R like this.
  3. WB5WPA

    WB5WPA Ham Member QRZ Page

    Yeah ... the BEST demo is when N4IS rotates his Waller Flag from Vert to Horz and back again on 80 meters.

    The voices rise up out of the muck and are decipherable when the flag is Horz.
     
    NU4R likes this.
  4. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I agree, good summary.

    Also, nearby power line noise is often most strongly vertically polarized because the arc current is conducted down the ground wire stapled to the pole. This makes a fairly good vertical antenna since the poles are about 30 to 40 feet high.
     
  5. K6HPX

    K6HPX Subscriber QRZ Page

    Thinking and analyzing, instead of parroting. A breath of fresh air!
     
  6. NK4K

    NK4K Ham Member QRZ Page

    OR, maybe the vertical is omnidirectional by definition, and at certain heights the horizontal antenna response goes figure-8 broadside, cutting signal by 6dB to 16dB+ off the ends. Thus, the total available omnidirectional noise signals are "ignored" or reduced under certain circumstances by the horizontal antenna. Seen it but never measured it. Don't quote me on the dB's lost (front to side ratio), because they change with height AGL and dirt conditions.
    Personally, my received noise is both horizontal, vertical, and oblique, and usually 40dB above the desired signal. DSP helps little. My electric company and cable TV company have never heard of Part 15, so I never get a break... even at VHF!
     
    Last edited: Sep 30, 2018
  7. KA1BSZ

    KA1BSZ Ham Member QRZ Page

    ok..here's my take on noise...back in the 60's-2000. I live in area where the power lines that acrossed my property were/are 40,000 volt supply lines.the road next to my house, us route 5, are 1200 volt lines. The substation was about 2 tenths of a mile away. I have a vertical for many years and the interference was so bad and it was 20 over s 9 24/7. After many times of complaints,they finely repaired the problem. Before they fixed the problem, I installed dipoles for 160,80, 40 and triband band beam and vhf beams for 6 and 2 and the noise went down to s9. so when the power company repaired the problem, power company fired the people that were giving me a round around with new people and they have been very helpful. Now I live in a hotel, where there is another noise problem...computers hash. my dipole ( g5rv ) picks up noise that is s9 24/7 and my mobile tarheel picks up hardly picks up any noise!!!! if any it is s2. I have a home made vertical that sits right over the computer room or close to it and it picks up about a s6. So I plan on putting up a vertical this next month. So the noise here at the hotel is HORIZONTALLY polarized. Most of the hams in our club say going with a vertical is NOT the answer,I say it is!. because the farther you are away from the computer room, the less noise there is! so for now, Ill keep on doing my hf mobile thing and when signals are over s9, I'll hear then on my kenwood 570 and dipole. 73 de KA1BSZ M VT.
     
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  8. AE7XG

    AE7XG Ham Member QRZ Page

    I like trying different configurations of antennas. What works for one guy won't work for another.
    Keep up the GOOD work and keep reporting your findings. Please.
     
    N0TZU likes this.
  9. W8AAZ

    W8AAZ Ham Member QRZ Page

    I got noise on 40, it won't go away, my antenna is horizontal and I pretty much am off the air on that band. Until the noise leaves again one of these days, maybe. Noise garbage will ruin ham HF eventually, I think. Too much garbage emitting too much noise and more comes along constantly and adds to it. It is sure spoiling ham radio for me. Noise is like roaches, kill one, and two more pop up.
     
  10. WB5WPA

    WB5WPA Ham Member QRZ Page

    re: "So the noise here at the hotel is HORIZONTALLY polarized."
    You are probably in the near or "reactive" field of the antenna with your noise noise source out to 1/4 to about 1/2 wavelength. For 40 meters this is 32 to 64 feet, for 80 meters this is 64 to 128 feet. Exact polarization within this distance doesn't mean much.
     
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