magloop

[kc5uta]

Dabbling in the magnetic loop realm. Built the first one out of a homebrew six meter Halo antenna, used flat aluminum cut for 6 meter 1/2 wave. I was kinda shocked how low it tuned. covered 40 through about 18. Tuning was incredibly tight though. Minimal capacitor adjustments made for wide swings in frequency. So...I built one out of approx 18 ft of 7/8 heliax. The first one was heard in Australia on 5 watts using WISPR (Im in Texas) Going to try to make a portable one out of regular coax next.

 

[K4EET]

A ham friend and I have built / are building mag loop antennas (MLAs). My friend has completed building his using RG-213/U and has been able to tune it from 80 Meters through 10 Meters. I am in the process of building one too. In my case, I am using LDF4-50A (1/2 inch Heliax from Andrews). Our tuning capacitors are different and mine will handle more RF power because they are out of a homebrew antenna tuner.

I would be interested in your build specs of your MLA and the component sizing of the various parts. Also, did you model the MLA before you built it and, if so, what software did you use? We have read just about every post on the Internet about MLAs. LOL! I find Dr. Carol Milazzo's, KP4MD, work with MLAs interesting and informative. You are probably familiar with her efforts. If not, her main webpage can be found at Amateur Radio Station KP4MD which links other webpages on her work with MLAs.

Finally, do you have any pictures of your 7/8inch Heliax monster MLA? TIA!

73, Dave K4EET

 

[ka3jjz]

And if you want to see other loop designs for us amateurs, then check out the Loops wiki

Loops - The RadioReference Wiki

wiki.radioreference.com

I will add that site to our page presently....

Mike

 

[K4EET]

Thanks Mike! 73, Dave K4EET

 

[kc5uta]

A ham friend and I have built / are building mag loop antennas (MLAs). My friend has completed building his using RG-213/U and has been able to tune it from 80 Meters through 10 Meters. I am in the process of building one too. In my case, I am using LDF4-50A (1/2 inch Heliax from Andrews). Our tuning capacitors are different and mine will handle more RF power because they are out of a homebrew antenna tuner.

I would be interested in your build specs of your MLA and the component sizing of the various parts. Also, did you model the MLA before you built it and, if so, what software did you use? We have read just about every post on the Internet about MLAs. LOL! I find Dr. Carol Milazzo's, KP4MD, work with MLAs interesting and informative. You are probably familiar with her efforts. If not, her main webpage can be found at Amateur Radio Station KP4MD which links other webpages on her work with MLAs.

Finally, do you have any pictures of your 7/8inch Heliax monster MLA? TIA!

73, Dave K4EET

Ill post one as soon as I have the build complete. The tuning cap is pop riveted wrong, and is hanging a little crooked hihi. I did not model it. I just used the 10% of 1005/ frequency loop formula with the coupling loop 20% of the primary loop as a start. THIS one tunes approx 3.2mhz to 16.8mhz "ish". I'm going to redo the coupling loop with rg213 and make it a few inches bigger, test it out.

 

[K4EET]

Ill post one as soon as I have the build complete. <snip>

Take your time. No rush... 73, Dave K4EET

 

[kc5uta]

well not really done...but here it is. it's roughly 6 feet in diameter. The coupling loop is at the top. Ill need to test it on a day off, outside, up at least 6 or more feet to get that "minimum one loop diameter " off the ground, and not inside a metal shop

 

[K4EET]

Hi @kc5uta and many thanks for the photo! I like the way that you used PVC pipe/couplings to support the Heliax. That is something that I have been trying to figure out — how to support the 1/2 inch Heliax that I’m using. Great 👍🏻 idea that you have there! Do you mind if I copy that support concept?

Another question… At the bottom of the main loop, it appears that you did not use connectors at the ends of the Heliax. How exactly did you make the connection to the tuning capacitor? It appears that you used screws to make the connections. Did you short the inner conductor to the shield of the Heliax?

That is a very nice MLA. Kudos on a design/job well done!

73, Dave K4EET

 

[kc5uta]

Hi @kc5uta and many thanks for the photo! I like the way that you used PVC pipe/couplings to support the Heliax. That is something that I have been trying to figure out — how to support the 1/2 inch Heliax that I’m using. Great 👍🏻 idea that you have there! Do you mind if I copy that support concept?

Another question… At the bottom of the main loop, it appears that you did not use connectors at the ends of the Heliax. How exactly did you make the connection to the tuning capacitor? It appears that you used screws to make the connections. Did you short the inner conductor to the shield of the Heliax?

That is a very nice MLA. Kudos on a design/job well done!

73, Dave K4EET

fyi...still a work in progress. Here we go.
#1. Copy away PVC is handy as heck!
#2 Heliax end connection. temporarily used wire and hose clamps. If you carefully crimp the ends to slightly reduce diameter (I used needle nosed pliers, in small increments to keep it reasonably round) you can make it fit a standard 3/4' copper pipe fitting. That was how I originally attached a trombone cap to it. (not enough capacity BTW)
#2 I Ignored the inner conductor.
In my final phase, I plan on re-soldering the 3/4 copper T's to the ends to allow a convenient way to add a sold spacer between the ends, and easy way to attach a weather proof box containing the cap. (gotta love copper tubing and plumbing fittings)