Horizonal Skyloop Antenna

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K5ERW, Jul 1, 2019.

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  1. K5ERW

    K5ERW Premium Subscriber QRZ Page

    Been looking at the ARRL Antenna Classics Antenna book and reading on construction of a 80 meter Look Skywire (80-10 meter) loop +160 vertical. This article refers to tophat of loading of the conductors of both feed lines being tied together. As a newbie to this my question is both the inter conductor of the feed line nd outer shield shorted to accomplish this ? See Illustration Quite from article "Both feed lin conductors are tied together (via shorted SO239 jack) the antenna is fed against a good ground." Can some one explain this to me.

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  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    Yes. Suppose you have a coax-fed horizontal loop that is more or less planar, with three or more corners, where the entire loop is 50ft above ground level. The coax comes straight down to the earth below the loop's feed-point, and then turns the corner, and runs some distance toward the shack.

    To operate on 160m, Cut the coax into two pieces, the vertical part and the horizontal part. At the break, install a dog house. Under the dog house, install a million or so on-ground or in-ground radials, each about a hundred feet long. Inside the dog house, connect the horizontal coax shield from the shack to the radials. Connect the shack coax to the input of an L-network tuner. The tuner output goes to the vertical coax where the center-conductor and shield are shorted together.

    When operating 80m and up, bypass the tuner, unshort the upper coax, and replace the tuner with a SO239 barrel.

    If the tuner is not an automatic, remote tuner, then you will be spending a lot of time in the dog house....


    Got It?
     
  3. AI3V

    AI3V Ham Member QRZ Page

    Yes, you short both inner and outer conductors.

    Essentially you turn the coax into a fat wire, with a big "capacity hat" (the loop)

    It's just a mechanical variation of a ordinary Marconi antenna.

    Please note that a "good ground" for such a antenna will be dozens of buried radials, each radial the better part of a quarter wavelength on 160m.

    Rege
     
  4. AD5HR

    AD5HR Ham Member QRZ Page

    If you want to use the loop on several bands, feed it with a
    balanced feed line (window or ladder) for much less loss than
    coax.
    For 160M, tie the two wires together at the tuner and use it as
    if it was a longwire. ( a couple radials for 160M will help considerably)
    I "load up" my skywire on all bands from 160M to 2M ssb.
    5BDXCC, 323 DXCC and DX on all bands except 60M, as I have
    no transmitter for that band.
    I have also found it to "load up" better if fed in the middle of one
    side, rather than at a corner.
    This is the only HF antenna I've had for 15 years, they work great for me.
     
    AC8UN likes this.
  5. W5LZ

    W5LZ Ham Member QRZ Page

    By shorting the feed line you effectively change that loop into just a single conductor, a random wire antenna. And like most random wire antennas you will need a tuner to match impedances at the transmitter end. (That loop turns into a very 'fat' wire, sort of.) Is there any particular benefit in doing this? A definte maybe. No promises.
     
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    Actually, the loop and its feed-line become a short "top-loaded with capacitance hat" vertical (Marconi). As such, it needs a good set of radials to work against.

    The "tuner" (matching network) should be located at the base of the vertical; not back in the shack. If the matching network (remote tuner) does its job, then the coax back to the shack and the radio will be operated at a very low SWR, i.e. low losses. If you try to tune it from the shack end, then that coax could have big losses, because it is being operated at a high SWR.

    If you run the shorted coax all the way into the shack, and try to tune it as a long wire, then you set yourself up for "rf getting into things in the shack", and for RFI from the house and shack getting into your receiver.
     
    Last edited: Jul 1, 2019
    WB5YUZ and K7TRF like this.
  7. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Yup, and to clarify that further the primary radiating element is the vertical feed line portion. If the top hat is symmetrical it contributes very little to the far field antenna pattern and the feed line tied together becomes the shortened vertical antenna.

    You can play this trick of tying together the feed line and feeding it against ground radials for other antennas like dipoles but the key is that the original antenna is primarily adding capacitive top loading and the feed line becomes the 'vertical' so if you have something like an 80m antenna up high with a long run of feed line it works pretty well as a top loaded 160m vertical using this approach. If you have a great big antenna but only a short section of feed line then this approach results in a heavily top loaded, but very short antenna with corresponding results in terms of antenna SWR bandwidth and efficiency.
     
  8. AA7QQ

    AA7QQ Ham Member QRZ Page

    Using relays, this can all be remotely done.

    Ed
     
  9. AH7I

    AH7I Ham Member QRZ Page

    I like the vertical plane loop for 80m works well on 40 too. Have not tried but opening the side opposite the feed makes it a bent dipole(think cobweb or Halo turned on side) for 160. Might put it up again and see how it does on 160 this fall. Vertical sides on mine are about 30-35 feet. 105' doublet is in place of the top wire right now..
     
  10. K8JD

    K8JD Ham Member QRZ Page

    I tried the 80 M dipole shorted for a 160 M loaded vertical, on a city sized lot.
    I could not get any 250 ft radials down without going thru the neighbors' backyards and under the road !! Just a few short radials was my best effort.
    It DID NOT work well at all, Best DX 500 Miles with a 559 report back.
    Then I MOVED !
    Now I have room for a halfwave dipole and can work coast-to-coast on 160 with a 100 W signal !
    Getting close to WAS-160 M ! :D
     

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