Re: Home-brew magnetic loop

Charles W. Powell

Not a problem Jim.  I have sent this enough times that I just need to copy and paste.  This tunes and radiates well on 17 & 20 meters.  Tunes well and radiates fair on 30 meters.  Tunes well and radiates poorly on 40 meters.  9’ is a good length for 15-17, with some compromise on 20 meters, and 6’ is a good length for 10-12 meters, with a compromise on 15.  Coupling loop is 20% of the full sized loop.

Chas - NK8O

Dimensions and materials

12’ LMR-400 for the main loop
2.4’ of copper tubing
Capacitor salvaged from an old Denton tuner that no longer worked
Electrical box for the capacitor
Various SO-239 connectors
1/2” schedule 40 PVC

Station in a bag (18” long)

Antenna parts in the bag

Laid out, ready to assemble

The base, assembled.  I now use a shorter extension for better stability.

Laying out the main loop.

And connecting the capacitor. Shield only.  Inner connector is not used.

Ready to make QRM from Riverside Park, Scottsbluff NE

And the rest of my station - KX3/PX3,  Macbook Air, 4.6 Ah LiFePO4 battery 

Me with the loop

Capacitor detail.  Ideally, an butterfly or vacuum variable is superior.

Coupling loop mounting details.  This is “new and improved” over the one pictured above.

12 gauge wire was used, soldered to the tubing after crimping, and the whole assembly pulled in as tight as possible.

SO-239 then soldered into place on the center post, and held with a screw and nut on the “ground" side.

On May 20, 2016, at 6:00 PM, 'Jim Crooke' crooke@... [4sqrp] <4sqrp@...> wrote:

Hi Chas,


I know it is quite a while after you sent this email, but if you still are willing to send me the pictures of your loop, I’d appreciate it.

School is out now and I am planning to play radio a bit.


73, Jim K0ESE


From: 4sqrp@... [mailto:4sqrp@...] 
Sent: Saturday, February 6, 2016 1:22 PM
To: 4sqrp@...; Charles Powell <doctorcwp@...>
Subject: [4sqrp] Home-brew magnetic loop



I just built my first magnetic loop antenna. So far, I am very impressed with the performance. The cost was less than 1/3 of the Chameleon and 1/4 that of the Alex loop. Except the capacitor box that I built at home with my electric drill, the framework was cut and assembled in my HOTEL room. If you are interested in great loop antenna that is easy to build, and costs < $100 if you have a tuning capacitor and < $150 if you have to purchase the capacitor, then send me an off-list e-mail NK8O at ARRL dot NET and I will send pictures with annotations on what I built. IT REQUIRES NO ADDITIONAL TUNER, and it is multiband. You can tweak it to your own needs.


Chas NK8O

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