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Thread: Magnetic Loop

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  1. #11

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    Interesting, normally they are orientated vertically, so it will be interesting to see how it works, it's a bit of a beast looking at it. It reminds me of the old Capital Radio on the old pirate ship King David that tried a loop antenna without much success.

  2. #12

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    If it don't work well we can always use it as a swimming pool so all is not lost.
    Last edited by AC2FO; 10-14-2012 at 03:17 PM.

  3. #13

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    Last week, he had the 3' diameter loop on top of tower at about 80' and it was oriented horizontally and suprisingly it seemed to work very well with contacts into indonesia thats what brought on this one.
    Last edited by AC2FO; 10-14-2012 at 03:16 PM.

  4. #14
    Join Date
    Mar 2003
    Location
    3763 Lyle Avenue, North Pole, AK 99705
    Posts
    22,661

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    It would be interesting to model the coupling between the loop and the tower itself. I suspect your tower's doing a bit of radiating too! If such is the case, your net result could be largely CIRCULARLY polarized, which has some interesting advantages on 160. See my recent QST article, "Three wrong assumptions about the ionosphere."

    Anyway....it's so refreshing to see something so bold, audacious, and out of the box. Please collect and record some objective performance data.

    Eric
    "The more you know, the less you don't know."

  5. #15
    Join Date
    Jan 2007
    Location
    San Antonio
    Posts
    132

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    If nothing else, it looks really really cool.

  6. #16
    Join Date
    May 2002
    Location
    Swimming pool in EL18
    Posts
    1,242

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    Quote Originally Posted by KL7AJ View Post
    Anyway....it's so refreshing to see something so bold, audacious, and out of the box. Please collect and record some objective performance data.

    Eric
    +1 on the above although I must admit I thought it was some sort of photoshopped hoax---wow, that giant loop is impressive and I'm glad to know that it's for real!

    73, Jeff

  7. #17

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    LOL, Yes it is for real, if you look you can see the capacitor .

    Last edited by AC2FO; 10-14-2012 at 09:22 PM.

  8. #18
    Join Date
    Feb 2004
    Location
    Bakersfield, CA
    Posts
    4,722

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    The proximity of the tower through the middle is a cause for concern as is the horizontal orientation If you have ever tried to get something that big in a vertical position and at least one loop diameter above ground then you have no idea what a difficult task that is.
    I use a magnetic loop daily on 40 meters and it'll tune down to 80/75 with no problem. In my operations on 40 meters DX is easily done. This depends on conditions but for those that have ever tried DX on 40 meters it can be an adventure at times. My loop is made of 1" copper pipe and is 40 feet in circumference. Mounted off the ground 11 feet up. Played around with a modeling program last night and found what everybody else has found. A greater conductor diameter will give you much better performance but at the same time the loop diameter becomes smaller. If you could make a loop 22.6 inches in conductor diameter and have a total length of 20.634 feet with a loop diameter of 6.571 feet then you'll have a loop that can tune MF/HF all bands. The Q on 160 meters will be over 5000 with a 3db bandwidth of just over 300Hz. The efficiency is just over 25% on 160 meters (not bad), 77% on 80 meters, 93% on 60 meters, 97% on 40 meters, 99% on 30 meters, 99% on 20 meters, 99.9% on 17 meters (the bandwidth has increased to 800KHz), 99.9% on 15 meters, and on 10 meters you still have the 99.9% efficiency with a ending bandwidth of 4.5MHz. This is if everything is perfect, and it won't be but it is interesting. If you add 1 milliohm of additional resistance then the efficiency drops from 25% on 160 meters to 15.5% and the Q goes from almost the 6000 mark down to just over the 3500 mark. Naturally if Q drops then bandwidth widens and it would now be 500Hz. This is just 1 milliohm. The loop I currently run has an added resistance of 3.5 milliohms which at 40 meters reduces the efficiency from 93% to 92.9%. Not worth worrying about and the effect of the added resistance at 80 meters drops the efficiency from 54.6% to 53.3%. Again, not worth worrying about.
    My magnetic loop is vertical and they work better in that position. Magnetic loops that are vertical do not do as well when raised up to 1/2 wave above ground. Horizontal loops need to be up 1/2 wave to work properly.
    I am intrigued by this construction. It took me days to get my 10 foot square loop up and operating (I'm getting old) and to have the ability to put one that large together is amazing in it's own regard.
    I would be interested in performance reports. Compare the antenna to another possibly a nearby fellow amateur running a dipole, an L, Vee , full wave loop and vertical and see how this antenna works at various distances.
    Let us know what you've found
    73
    Gary

  9. #19
    Join Date
    Oct 2010
    Location
    U-Tapao
    Posts
    1,529

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    Quote Originally Posted by AC2FO View Post
    If it don't work well we can always use it as a swimming pool so all is not lost.
    I think you are on to something. You gave me an idea, what about taking a large galvanized swimming pool and cutting the bottom out ?? !! I like it, that would be a nice loop antenna.

  10. #20

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    Quote Originally Posted by KO6WB View Post
    The proximity of the tower through the middle is a cause for concern as is the horizontal orientation If you have ever tried to get something that big in a vertical position and at least one loop diameter above ground then you have no idea what a difficult task that is.
    I use a magnetic loop daily on 40 meters and it'll tune down to 80/75 with no problem. In my operations on 40 meters DX is easily done. This depends on conditions but for those that have ever tried DX on 40 meters it can be an adventure at times. My loop is made of 1" copper pipe and is 40 feet in circumference. Mounted off the ground 11 feet up. Played around with a modeling program last night and found what everybody else has found. A greater conductor diameter will give you much better performance but at the same time the loop diameter becomes smaller. If you could make a loop 22.6 inches in conductor diameter and have a total length of 20.634 feet with a loop diameter of 6.571 feet then you'll have a loop that can tune MF/HF all bands. The Q on 160 meters will be over 5000 with a 3db bandwidth of just over 300Hz. The efficiency is just over 25% on 160 meters (not bad), 77% on 80 meters, 93% on 60 meters, 97% on 40 meters, 99% on 30 meters, 99% on 20 meters, 99.9% on 17 meters (the bandwidth has increased to 800KHz), 99.9% on 15 meters, and on 10 meters you still have the 99.9% efficiency with a ending bandwidth of 4.5MHz. This is if everything is perfect, and it won't be but it is interesting. If you add 1 milliohm of additional resistance then the efficiency drops from 25% on 160 meters to 15.5% and the Q goes from almost the 6000 mark down to just over the 3500 mark. Naturally if Q drops then bandwidth widens and it would now be 500Hz. This is just 1 milliohm. The loop I currently run has an added resistance of 3.5 milliohms which at 40 meters reduces the efficiency from 93% to 92.9%. Not worth worrying about and the effect of the added resistance at 80 meters drops the efficiency from 54.6% to 53.3%. Again, not worth worrying about.
    My magnetic loop is vertical and they work better in that position. Magnetic loops that are vertical do not do as well when raised up to 1/2 wave above ground. Horizontal loops need to be up 1/2 wave to work properly.
    I am intrigued by this construction. It took me days to get my 10 foot square loop up and operating (I'm getting old) and to have the ability to put one that large together is amazing in it's own regard.
    I would be interested in performance reports. Compare the antenna to another possibly a nearby fellow amateur running a dipole, an L, Vee , full wave loop and vertical and see how this antenna works at various distances.
    Let us know what you've found
    73
    Gary
    Have modeled several loops horizontally @ 80' with eznec and they seem to produce a lower angle and more gain than a verticaly oriented loop at same height.

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