Magnetic Loop Question

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W8NSI, Nov 22, 2016.

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  1. W8NSI

    W8NSI Ham Member QRZ Page

    I just checked and the wire I intend to use is #6 wire, just a shade over 4mm diameter. It will not be possible to wind it through a toroid so I will be using a ferrite rod which makes it a bunch easier to wind. Also the loop on the coax can be adjusted more easily too.
  2. WA4SIX

    WA4SIX Ham Member QRZ Page

    I would suggest the Magnetic Loop Yahoo group for that technical stuff. I just mash stuff together.

  3. AK5B

    AK5B Ham Member QRZ Page

    ...and the ohmic loss one has to worry about are those potentially within the radiating element---not the feed coupling---that's why it is so important to use a continuous element as opposed to pieces of pipe soldered or bolted together.
  4. WA4SIX

    WA4SIX Ham Member QRZ Page

    Looks to me that he is using some form of pipe connected to the #6AWG wire. The wire loops around the ferrite rod for transformer coupling.
    Is the whole loop going to be built from the #6 wire? If so, it will be thin for HF.
    Most using a ferrite transformer run the loop conductor (My preference is 7/8" hardline with an OD of about an inch) through the middle of a torroid (As the primary) & experiment with the number of turns on the torroid with wire connected to the feedline.
    If you could give us some more details, we could help you better.
    1. Frequency
    2. Proposed diameter of loop material
    3. proposed loop circumference/diameter

    I will be getting to a final build next week, hopefully.
    I will have a 3' diameter loop for 15-20 meters & a 2 turn loop at 5'-6' diameter for 40/80 meters. Both will be constructed from 7/8 heliax for the loops.
    Both will have a torroid transformer with relay switchable taps to the feed portion of the torroid transformers.

  5. AI3V

    AI3V Ham Member QRZ Page

  6. MM6IXH

    MM6IXH Ham Member QRZ Page

    I recently built a six meter square dipole with a butterfly capacitance at the middle plastic T joint with gama match for swr seems ok I only made it as I bought a Icom 726 and it has 6 meters built in. I am still learning the ham game but as a fabrication chap in the distillery trade I am at the begining of building a mag loop and wonder if my info is good .First up I was told to use 7/8 or even 1" copper at a length of 16 ft-- rolling it is no problem,next the variable capacitor I got a high voltage 150 pf on e,bay not wanting to spend too much money hope it will tune to 7 mhz and 14 mhz. The drive motor a 2 rpm worm drive which I hope will stop and brake and hold ,controlled with a simple toggle switch to reverse polarity, and a ark of plastic with micro switches giving position indication and stop indication. The primary feed loop I planned to use 3/8 copper pipe.....or have I got it completely wrong.

    Cheers Robbie fae Scotland
    AK5B likes this.
  7. AK5B

    AK5B Ham Member QRZ Page

    Scroll down (there's a lot to read and see on Rich's page) and see what his helically-loaded version of the DDRR family radiators---really cool and about the most ideal stealth antenna ever conceived, in my opinion. I have often toyed with the idea of building one but in my situation signals would be blocked from the SSW all the way through SSE due to my condo building's proximity and the fact that these type of antennas are vitually on the surface on the ground. Oh, if only I had a flat roof!

    Thanks for posting the link to Dr. Boyer's earlier designs that are truly incredible, Rege---I really enjoyed reading about them again and be reminded of what is possible in terms of compact stealthy antennas.

    Now I'm heading back outside to continue work on my 15-17-20M small loop (which, by previous experience has proven itself worthy despite my restricted and somewhat blocked QTH.

    73, Jeff
  8. AK5B

    AK5B Ham Member QRZ Page

    Ay, Robbie you're on the right track. 7/8th or 1" continuous copper tubing or pipe is certainly better than anything smaller. The skin effect has much to do with the element size (outside diameter) and if you can roll a 16-foot circle out of that you'll end up with a great loop for 20-40M. Your capacitor sounds like it is about the right value without looking at my trusty KI6GD online loop calculator (recommended to get anyone in the ballpark that's building a STL; one can enter the element type and diameter, wattage and so on and lots of design parameters will be revealed).

    You might want to take a look at my revived thread about my 10-20M loop that I am re-building as a 15-17-20M loop now ("My QRO STL for 10-20M is finally done" is the title) for a bit of extra guidance or ideas---although I think you've already got it pretty well sorted.

    Btw, my dad's dad came from Kirriemuir/Forfar just north of Dundee. Lovely place I hope to visit again someday.

    73, Jeff
    K6CLS likes this.
  9. MM6IXH

    MM6IXH Ham Member QRZ Page

    Thanks for the help Jeff when you boys come to Scotland there is only one problem you dont want to go home, aye , this is a good site for help I enjoy coming on here.

    Thanks Robbie QTH here is Lossiemouth in the N.E coast.
  10. AK5B

    AK5B Ham Member QRZ Page

    You're welcome Robbie; must be nice to work in the distillery trade, too. All that beautiful copper and single malt about!

    I trust you are going for your ham ticket soon?

    Let us know if you have further questions anytime.

    True, I did not want to leave the land of my ancestors but I also had further work to do over on the continent---at least I got to spend some time in Glasgow, Kyle of Lochalsh, Inverness, Edinburgh and Forfar/Glamis before I boarded the train to bloody England, ha ha!

    Being on the coast (I see Lossiemouth is up the road from Inverness) you'll be in a great spot to work EU and beyond; saltwater helps with vertical polarization which is what our small loops produce (generally speaking).

    Cheers, Jeff

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