I wanted to thank you for your presentation. I learned more about loop antennas from you than anyone else. I was getting frustrated with my commercial small loop that tuned a low SWR at 40 meters but nobody could hear me. I replaced my coax radiator with an all aluminum radiator and conductor to increase the antenna efficiency this evening and tonight made made a DX contact on 40 meters with Italy with 25 watts. I am grinning ear to ear that I watched this, learned something, made a change, and it works! I am keeping this loop configured for 40 meters and my second coax loop for 10 and 20 meter bands. It has me thinking about getting a square loop put together and tune that specifically for 20 meters. I primarily enjoy QRP work because it is so challenging and everything has to be set up perfectly. Thanks again…. KD2ZTA

What a wonderful presentation! You guys did a great great job. To the hardware store Robin! Theres PVC pipe just waiting to be whacked and drilled!

Outstanding material, Thanks so much!

I've get started to build one 🤗 Thank you for sharing!

Thank you, that was so enjoyable and educational, Learning is exciting at any age, with wonderful teachers.

I have learned new stuff, thanks for sharing!

Excellent thank you! I got my ham licence in 1957 too! I was VE6KX then, now VE7YJ.

Great talk and experience, thank you

Forgive me for pointing the following out, but John used the word circumference as well as diameter (3 times for diameter) when describing how a loop can be more than 1/10 of a wavelength, which did he really mean? Loop diameter is diameter, circumference is the amount of conductor end to end which the loop is made from, the two terms cannot be used interchangeably. I suspect he simply misspoke on that point.

Really interesting presentation. With the conductive tape on pipe, how do you ensure a good conductive join at the corners? Especially with aluminium I'd be concerned about just a mechanical contact.

What about multiple-turn loops? It gets the current up by repeated low current turns, so I^2R goes as low as you want it.

Thank you! This a rare gem of a video. Lots of great practical advice backed by data. One question... for those of us who are receive-only, how much of this is relevant? For instance, the MLA 30+ mag-loop antenna ships with thin wire. Would it benefit from a 2 inch conductor or is that for tx only?

I was under the impression that the 1/10λ came about because you want a constant current around the loop thus maximizing the field. He also glanced over the coupling used in the original Army Loop (capacitive coupling). Fernando N2FQ/6

Fantastic info! How about feeding the loop with window line or open wire?

outstanding

Can you ask John to provide a written and more detailed account of the building process? Is there any actual comparison between loops, done in real life and not in a FEM simulator?

I made a flat plate capacitor using PVC as the dielectric. I found that the capacitor got very hot after operating for a while. To me this indicates that PVC is lossy at RF frequencies. Does your loop get hot in the area of your capacitor ?

At 16 min, having a bigger conductor for a bigger loop means < 24:1 I think, not > 24:1. If the diameter grows you need a bigger pipe. So the formula should read > 1/24 ..

Question: What power was used in the efficiency measurements at 7:20 and 9:50? If you are running QRP, won't those curves look very different since you are far less likely to saturate the surface of the conductor with charge?

Thank you. This is some good, common sense info. But I do have a couple questions and a comment. What elevation above the ground did you use for your loop's null models? What is the bandwidth without retuning, meaning what is the Q, since the PVC dielectric will reduce it compared to an air- or vacuum-variable cap? And the comment: A round loop has a lower resistance for its cross-sectional area and thus a slightly higher efficiency since a circle has the maximum possible area for its circumference.

what are you guys thoughts/opinions on: instead of using a cylinder shaped conductor, you use flat stock shaped conductors ?

Can multi-turn loop antennas have a 200kHz bandwidth?

when I measured the resonant frequency of a loop with no capacitor I found it resonated where its length was 1/2 wavelength. It was like taking a dipole and wrapping it into a loop. I put 100 watts into it and could light a 4 ft long fluorescent tube with it. The loop was about 9 feet long and resonated in the 6 meter band. 6m was dead at the time so I did not try making any contacts with it. So what does this actually tell me about the frequency that it would work on as a mag loop?

Hello. If I understand correctly, a loop antenna does not work at lower frequencies. I want to use a loop to receive channels at the top of the medium wave band. Between 1.6 Mhz and 1.7 Mhz. I bought an MLA-30+. Will that work? Do I need to change anything for a better result? Greeting. Cees

Thank you for this very clear description. Still I have a few heretic questions. When you say that diameter matters, I understand that there is the skin effect. But does this effect not also matter for a normal dipole? So, why using wire for dipoles, but tubes for magnetic loop antennas? Next: how to connect the copper coax cable to aluminium? Is this possible at all? Finally: Because current is high in a loop, all connections are critical. When you make the loop out of one aluminium foil, it is ok, but connect them just by pressing, is this enough? Best 73, Roland AB7SN / DL9NBX

So are multiple loops a way to compensate for the conductor size?

I am not clear on the way your feed loop is connected. Is the feedpoint connector connector connected to the loop, and the other side, the u bolt, inductive? or is it conneccted by a bolt to the aluminium? or just an independant loop altogether?

how do i connect the wires from the 239 to the anntena? I'm not an engineer, help me out here.

I'm sure it will work, however it is durable having it out in all types of weather? Wouldn't that covered foil paper peel off over time when exposed to the elements and also applying heat. In theory you may be correct, however I would look at durability. Pretty interesting video. Best regards. 73.

I’ve been told that this construction (aluminium foil on pvc pipe) would be too lossy on 10w. I’d like to know for sure.

r John Portune, W6NBC , Thank you for this very informative lecture ; "Looking for the optimal magnetic loop antenna". We live on an apartment with and small balcony on S-W of 7 m2 , so an ideal antenna ! I built a MLA the classic circle shaped diameter 1 meter from 1,5cm plumber pipe. At the bottom of the circle a variable air capacitor 20-250 pF and at the top of the pickup loop 20% of the circumference of the main loop. This MLA works on the HF 10 - 20 M My favorite HF bands. My question , I would like to recreate your design of the optimal magnetic loop antenna for Hf 10-20 M bands, but due to my poor eyesight your drawings are not easily visible. Do you have a printable version of the construction description ? Or possibly where are these for sale , Amazon ? That would be very nice ! 2nd question, my built classic MLA where is the biggest improvement factor ? Best regards from the Netherlands, Theo PA0HTY , 73 Translated with www.DeepL.com/Translator (free version)

Have these components ever been used successfully? 2 in. x 3 in. x 10 ft. White Aluminum .0145" Downspout $12.98 each 2 in. x 3 in. White Aluminum A-Style Downspout Elbow $4.28 each Wirebush the paint and use Pop-Rivets on the elbow connections?

So how many watts can the loop take?

Wouldn't it have been a lot easier to use a piece of plastic tubing bent into a circle then just wrap a strip of the foil tape around it?

very nice presentation. excellent information. 73 N 9 I Z X

CAN WE USE THE BELOW ?

Funny how non ferrous metals become magnetic though never understood how aluminium can resonate and also copper surly Loop Antenna is enough magnetic seems a breach of the trades description act no one calls a di pole a magnetic di pole?

The more turns you have on a magnetic loop, the more efficiency you get. Ad infinitum? This is rubbish. There is no such things as a free lunch. What about the area? A lot of what you said about magnetic loops is true, but this is not at all. Stop quoting Maxwell, if you don't understand it.