Loop-On-Ground Antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Aug 1, 2018.

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  1. WN6F

    WN6F Ham Member QRZ Page

    Will do! Although trying to model an elevated steel roof next to my antennas is beyond my ability. :)

    Elevation (air gap) update!
    Internet anecdotal I know ....

    1) Hearing a few 160m cw contesters in neighboring 7 district at 3:30pm in the afternoon! Big guns for sure..

    2) 80 meters - when totally on ground, I noticed that there was an obvious change in band noise when quickly going from the low end to the high end of the band. So much so, that I always readjusted my volume a little bit to compensate. Not any more - band levels are the same from low to high.

    3) 160m - other than the possible fluke of big-gun contesters above, my normal band level noise is equal across the band from low to high. The little "dog" version with no matching had me toggling the secondary preamp on and off depending. Now I think I can live without toggling in the secondary rig preamp. Yet still to early to really tell.

    Heh, maybe N6LF was onto something! Purely anecdotal report from me I know, but it's what I've observed so far.
     
  2. K4SAV

    K4SAV Ham Member QRZ Page

    I don't think that modeling your conductive shingles will help much with this problem, but knowing how to do that may help with other situations where you need to model a large plane, like a metal roof, that maybe has a vertical sitting on it. Implementing a whole bunch of small wire squares to simulate a plane will take a lot of wires and a lot of patience. There is an easy way to do this

    Create several horizontally wires and make them equally spaced vertically. Then assign them the number of segments that will make the segment ends occur at predictable dimensions, like whole numbers instead of complex fractions. Example: a 10 ft wire with 10 segments will have segments ends hitting on lengths of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 ft.

    Then create several vertical wires on top of the horizontal wires and make them evenly spaced horizontally, actually spaced horizontally the same as the length of each segment in the horizontal wires. Then assign them segment numbers that make the segment ends hit on the horizontal wires.

    The segment ends of both the horizontal and vertical wires must hit at the same places. If you miss, EZNEC will complain. Doing it this way a plane can be simulated with only a few wires.

    Segment lengths need to be very small compared to frequency wavelength.

    Jerry, K4SAV
     
    Last edited: Jan 26, 2020
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    AutoEz has a built-in wire-frame grid creator that I use to build the model shown here. It is just a matter of specifying its length, width, orientation, how many wires, how many segments per wire, etc...

    If you are using EzNec, I can build the wire grid for you and you can import it into your existing model.
     
  4. N9LCD

    N9LCD Ham Member QRZ Page

    "Loop on ground" sounds interesting for an antenna-challenged QTH.

    Any thoughts about a "LOOP ON FLOOR" for HF operation -- some solid magnet wire around the floor of the living room into an antenna tuner.

    Yeah. I know, noise etc. But this sounds like an opportunity to get on HF without tearing the house apart to go "outdoors".
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    The LOG folks are talking about is a receive antenna with terrible transmit efficiency. Folks have made horizontal Small Transmitting Loops(STLs) set just above the ground but they're a more involved project and I wouldn't want to run one indoors at much more than QRP levels. For someone interested in going down that path you might as well build the same antenna and run it as a vertical oriented STL.
     
    N9LCD likes this.
  6. WN6F

    WN6F Ham Member QRZ Page

    Thanks for the modeling offers and info guys - hang onto that for now and I'll look you up when I get back into that aspect..

    Elevation update: So the slight elevation of the wires seemed to help on the 36 foot dipole on ground, much more than the 60 foot log. It helped me realize that I need to keep an eye on degradation over time of the wires getting sunken into the actual ground or overgrown.

    Basically I'm happy with either one, with or without secondary rig preamps. Seems to just make things louder where I have to rock back the rf-gain or af gain for no real improvement in audio recovery. To each his own, and refine as needed.

    BUT, now being slightly elevated at no more than an inch, we have the practical problem of mowing and weed-wacking getting tangled in the wires.

    Rudy N6LF pointed out in his article about the difference between dropping wires into a slot in the ground, vs actually backfilling that slot over the wires - and laughed at the suggestion that one could put a bog inside pvc - but that it could be done because of the all important air-gap between wires and actual earth.

    So totally impractical for a 200 foot bog (yeah yeah, really a "wog"), but for our little antennas, putting wires into say 1/2 inch pvc and dropping them on the ground, OR maybe just burying it just below the surface without entirely covering the top with soil might protect from lawnmowers and whatnot.

    I think I'll take a break from experimenting and enjoy listening for awhile, but when I bring home some pvc to enclose the wires in for testing, I'll let you know!
     
  7. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    This reminds me of an article I read years ago by a UK ham who experimented with a buried antenna in plastic pipe underground. I can’t find it now.
     
  8. KJ4VTH

    KJ4VTH Ham Member QRZ Page

    You'll just have to dig it up. ;)
     
    KC3KWA, KD9PAI, WB5YUZ and 3 others like this.
  9. KM4DYX

    KM4DYX XML Subscriber QRZ Page

  10. AJ5J

    AJ5J Ham Member QRZ Page


    Hmm, I'm already thinking that this may be a dubious idea at best (note that Alfred E. Neuman is pictured on the 2nd link above).:D

    There is, however, a good article in an older RSGB book (I've had since about 1994) that describes a buried antenna experiment with the wires suspended inside some clay pipe, though. The title is :

    Practical Wire Antennas - Effective HF Designs for the Radio Amateur by John D. Heys, G3BDQ

    Slightly off-topic but will also mention that a pair of 40m receiving loops that KY6R uses with an NCC-2 looks like a very easy to build and is directionally effective---check out his QRZ page if interested, too.
     
    Last edited: Jan 26, 2020

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