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5 Foot Diameter Magnetic Loop Antenna
18 March 2013 | by 
A bonus picture here. The one on the left is a 3 foot in diameter loop.
Note: The little box at the bottom of the small one contains an air variable capacitor for tuning.
Compare it to the 5 foot in diameter loop on the right. ‘
5 Foot Mag Loop
I made a QRP CW contact with this mag loop from right where it stands in my drive way.
Small Loop Feeds the Big One
Home Made Capacitor Clamps.
Home made cap clamps. The clamps are soldered to keep the contact resistance low.
This is very important with High Q antennas.
5 to 150 Pfd capacitor
Russian capacitor. It is available at E-Bay for about $150
Easy to Make PVC Pipe Stand
Where would hams be without PVC pipe!
This stand is made from 2 1/2 inch sewer pipe.
This is a fun antenna to build and use. I made my first contact with W9GY this afternoon on 20 meters. I used 5 watts, he used 10. RST out was 459, RST in was 579. The antenna was in my drive way in front of the garage that you see here. And Jeff was in Indiana. What a hoot! Making contacts on a home made antenna is great fun. The parts are readily available and with a little planning and shop time you can have a Magnetic Loop antenna to play with.
This is my second Mag Loop. The first one is 3 feet in diameter and covers from 20 through 15 meters. I’m planning another for 17 meters through 10 meters. Mag Loop calculator is available at http://aa5tb.com/index.html
Yahoo has Mag Loop groups that are very helpful to get you started. http://groups.yahoo.com/group/MagLoop/
and http://groups.yahoo.com/group/MagneticLoopAntenna/
Copper foil or strapping is available at http://stormgrounding.electrical-insulators-and-copper-ground-bars.com/copper-foil-2.html
If you’d like more information about Mag Loops, please feel free to contact me. [email protected]
73 De AA1IK
Ernest Gregoire
10 Responses to “5 Foot Diameter Magnetic Loop Antenna”
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Looks good Ernest! I’ve had people ask me about Magloops, and I’m no authority. I’ll refer questions to you.
73 de W2LJ
Which band(s) is this one for? And which band was your QSO on? It looks like the capacitor costs substantially more than all the rest of the parts combined.
The contact was on 20 meters. Sorry, I forgot to post that originally! This one covers 80, but just barely, through 20 meters. 40 is pretty weak too, but I think that might improve when I move the loop higher; like to my porch on the third floor of my condo.
With limited space becoming more the norm for hams these antennas may end up taking off in the near future.
Mike
Every time I go to the big hardware store I shake my head at what it would cost to build even a simple J-Pole for 70cm. I’m just starting to research the magnetic loop but is it true they have a very small range before retuning with a tuner is needed? It’s not a deal breaker but something I’ve wondered.
Greg, KA2COP, The short answer to your question is, ‘that depends.’ It depends on the diameter of the loop, the size of the conductor of the main loop and the band of interest.
Got to AA5TB’s web site and ‘roll your own’ at various frequencies, and diameters, and pipe size. The basic rule of thumb is the smaller the main loop diameter, the more narrow the bandwidth. Like wise for the size of the main loop conductor, the smaller the size the narrower the bandwidth. Just pick one you can live with, 20 meters is a good start, and you don’t have to use a ‘Russian cap’ either.
There are suitable caps for sale on E-bay for qrp purposes. Keep in mind that as the power increases, the voltage across the cap also increases. Even at QRP levels you can get 1,000 volts across the cap, depending on the frequency of course.
Both look great. Interested in making a loop for 6 & 10. Would the 3ft work or do I need to go to about 4? Using old RS HTX100 mobile for base.
Art, KI4OYV, use this calculator to figure out the size of the loop you want to build and how to feed it properly. I like the Gamma Match best, quick, easy and it works.
http://www.aa5tb.com/loop.html#cal
Loops are a high Q antenna, everything you do, build, add, will affect it. Balance, is the key word here. Weigh one thing against the other. Don’t expect perfection right off the bat, but please do, try these antennas.
They are fun to build and fun to use. When you get into the calculator, you will see what I mean about the trade offs.
de AA1IK
Ernest Gregoire
Hi I live in an apartment and I have been trying to find some kind of antenna I can use indoors because I can not put one up outside I hade to move from my home town of Bristol to Nashville because of health reason. Where I live at I had outside antennas. Some hams in my home town help me put them up I am in a wheelchair and can’t walk I have cp. I have been a ham since 1977. I have a vertical super stick now dosen’t work well at all. I have looked all over the internet to try to find drawings on how to build a magnetic loop antenna that will cover at least 40-10 meters I know mfj makes one but you must understand when you live on 751.00 a month and you pay 300.00 of that in rentand about 100. in co pan in meds. the food. That don’t leave much left and the mfj antenna cost almost 500.00. I have seen many types of magnetic loop antennas on line only thing is none of them really tell you how to build one or if they do they put in ways not many would understand. I went to technical school got my engineers degree in electronic but its been a long time since I studied antenna theory and then only not much then. Back when I went to school we were steal used tubes in a lot of things. So if you can help me out I would appreciate it and if u could tell me where to find the variable capacitor for the loop the rest I can get here if u can tell me low big the loop must be and what parts I need to build it and maybe draw a picture or something of how to put it together. I will be glad to pay you for your time just tell me how much then I will tell you weather to go ahead or not if its more then I can I can pay then will forget it. Thank you for your time in reading this e-mail.
Clarence N4-GFD
More information needed please! How much power can be used?
Most loop designs can’t handle a typical 100 watt CW rig.
How about a schematic? How do you adjust the capacitor?