How to bring this horizontal loop to resonance on 160m?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by 2E0ILY, Mar 25, 2019.

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  1. 2E0ILY

    2E0ILY Ham Member QRZ Page

    I have taken some screen shots from my AIM4170C antenna analyser of my
    corner window line fed horizontal loop showing its mismatch on 160
    meters, would anyone be able to suggest what to do with the
    feeder length to perhaps bring it into resonance please?

    I have, for
    some considerable time, been using the feeder, strapped together at
    the base, via a matching and loading coil, with the loop as the "top
    hat" on LF only. I now want to unstrap the window line feeder and resonate it on top band. The analyser shots seem bizarre but I calibrated it before I started. 3 shots, one at the shack end of the window line feeder, no balun, one same place with 4 to 1 balun, one same place again with 9 to 1 balun. Comments greatly appreciated, thanks.
     

    Attached Files:

  2. WA7ARK

    WA7ARK Ham Member QRZ Page

    How long is the feedline?
     
  3. K8JD

    K8JD Ham Member QRZ Page

    Loop Questions
    Pretty hard to argue "resonance" with a hi Z balanced feedline. The idea is the high SWR conditions will not give much loss in a high Z line and then use a good balanced input tuner that matches Z to rig in shack. This makes more sense when you try to use the ant on multiple bands !
    I have a FW loop up horiz for 40M and used a Q section of 75 ohm Coax between the feedpoint of the loop and 50 ohm coax to the rig. That got me to a very low SWR.
    I used the formula... Wire L (in Ft) = 1004/F (in MHz) to get the wire length of the loop.
    Is low SWR the actual concern ?
    Another thought , on the lower bands you will be a small fraction of a wavelength above ground (usually) and this will lower the effective frequency of any wire antenna and you will have to shorten the total length of the loop by some amount to get the operation freq back up.
    It was easy to do this with just a SWR meter on my system , with the Q section Z matching and Coax feedline.
     
    Last edited: Mar 25, 2019
  4. K8JD

    K8JD Ham Member QRZ Page

    Your screen shots make no sense with no freq scale showing.
    WELL.....
    I had to magnify them, and then I saw the freq scale, looks like the wire is getting the ground effect and has to be shortened ! Just like I mentioned in my other comment.
     
  5. KA9JLM

    KA9JLM Ham Member QRZ Page

    Corner window line fed horizontal ? Do you want Cloud warmer ?

    A change in feed point can make a lot of difference. I would try center fed, To match the direction that you want your signal to go.

    I just use coax to feed my 1 wavelength loops. Works great for me, Feeding in the center of one side.

    Good Luck.
     
    Last edited: Mar 25, 2019
    WB5YUZ likes this.
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    Also,

    What kind of feedline?
    Your best guess as to the overall height of the loop?
    Your best guess as to the total length of wire in the loop?
    Where is the loop fed? Corner or side?
     
  7. W5LZ

    W5LZ Ham Member QRZ Page

    Probably the "best" antenna I've had was a very un-regularly shaped full wave on 80 meters. It was fed with 450 ohm ladder line through a tuner. I have no idea what it's radiation pattern looked like, since it was "low" in height it was probably a typical "ball". For higher bands that pattern was who-knows shaped! It did what I wanted it to do so that was all that mattered. Could it have been improved? Of course! But not with the supports I had to work with. The only band it had a problem with was 15 meters, which I didn't use anyway. Would the same antenna work for others? I sort of doubt it...
     
    AA7TV likes this.
  8. AA7EJ

    AA7EJ Ham Member QRZ Page

    Can you post ANY Rx/Xcl at a frequency? The graphs are hard to read.

    If you had matching setup / coil before you must have calculated it from some data , right?
    Perhaps you could start with a model to get the impedance you need to match.
    Hope the group can stay with "match resonate loop on 160 " and not getting sidetracked with mutiband / making DXCC etc
     
    SM0GLD likes this.
  9. 2E0ILY

    2E0ILY Ham Member QRZ Page

    About 35 feet, hangs in a slack loop, down from the corner then looping up to the 1st floor shack window.
     
  10. 2E0ILY

    2E0ILY Ham Member QRZ Page

    I have uploaded the scans to:

    http://www.chriswilson.tv/no-balun.jpg

    http://www.chriswilson.tv/4to1-balun.jpg

    http://www.chriswilson.tv/9to1-balun.jpg

    Thanks
     

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