A Small Space 40 Metres Antenna: The Full Wave Loop

Thanks to Dave, EI2HPB for emailing me and describing his proposed antenna.
What a great antenna taking up 70% of the space that a half wave dipole would.
Let’s look at how we can change its radiation patterns by changing where we feed it from.
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[@WECB640]

Tim, never stop experimenting and learning. The modeling software has helped you immensely and you've done an excellent job sharing your findings with us on YT.
As a famous M.I.T. professor once stated at the end of his lecture series...
"This is like a disease.
You can't resist it.
And it's all my fault.
I can not cure you anymore.
It's too late for that.
This is a disease for life.
But all this joy and fun that you will get over and above the everlasting beauty of the bows, you will see much more than people who do not have the knowledge that you have now. And therefore the experience for them will be rather shallow.
Knowledge always adds.
Knowledge never subtracts.
Knowledge is hidden beauty.
Your life, will never be the same."
73 OM

[@timg5tm941]

Wise words and thank you!!!

[@user-sf6oc5cz7c]

Put up a 40m loop fed through 4:1 balun. Real haphazard irregular triangular shape. To my amazement the vswr readings for 7, 14, 21 and 28MHz were all less than 3:1. I had a ball over the winter using it and max 50 watts working HF - previously mainly VHF. Worked my first VK ever - 52 years it took me! Why I’d never tried one before, I don’t know, but my ‘go to’ aerial for a small garden is now the 40m loop.

[@timg5tm941]

Great insight thank you

[@bazzaar1869]

I ran this antenna though most of the 90s. It worked well but not for extreme 40m DX(VK,ZL from UK) What MUST be said about this antenna is it works on ALL bands above 7 MHz! It really performed on 20 and 15 as I remember, even WARC bands had lowish impedance that my TS530(valve PA) could tune into. You feed with a 4:9 balun, yes 4:9, it is a thing, look it up, and have about 20 feet open wire feeder from balun to feed point. Mine was fed at the top centre, so basic horizontal polarisation. Well worth the effort, and it did exhibit the famed low noise on receive property.
73 de G0AFV

[@timg5tm941]

Great points thank you

[@davecarty6503]

Fantastic Tim, exactly the info I was looking for and so well explained... hopefully give food for thought to other hams with fairly restricted space and who might fancy a low loop as an option for 40m... not sure its really worth the extra trouble and wire when you see the comparison with a dipole but thats what I wanted to know, also interesting that the impedance at the corner is almost the same as feeding in the centre of the bottom wire.. thank you so much for taking the time to run this through the modelling software, very much appreciated... best 73s and chat soon de EI2HPB Dave

[@timg5tm941]

My pleasure Dave!

[@TheSmokinApe]

Nice video Tim, I enjoyed the analysis 👍

[@timg5tm941]

Cheers Ape!

[@JxH]

If the rectangular loop was installed with *pulleys* (or equivalent) on the supports at the corners, then the loop could be slid around effectively relocating the position of the feed point in relation to the geometry of the rectangle. Presumably, since the current and voltage nulls and peaks are being relocated relative to the feed point, then this technique could help fine-tune the match.
If taken to the extreme, it might have other effects such as the direction of the gain lobes and nulls.
Cheers.

[@sc20910]

I love this info. Really want to see / hear about some real world performance next.

[@izzetmuroz]

Nice one mate keep up the good work 👍

[@timg5tm941]

Cheers!

[@brianfields4479]

Loops are great on rx also compared to many ants, I use a vertical for tx, and a loop low to the ground on rx. My old 40m vertical loop up high, was still, not quite as good as a vertical. 73 zl3xdj.

[@corsavic1]

great vid keep them going thanks mate

[@timg5tm941]

Thank you!

[@F4LDT-Alain]

Welcome to the G90 Users Club, Tim! 😉
Best 73

[@timg5tm941]

Yay!

[@Kinetic79]

This is great. Seems much easier to feed at the corner, and very very decent performance compared to the vertical. Better than I had expected. 👏🏻
I wonder if the length and height of your rectangle affect that much(?)-would you have to go to the extremes to start to see big variations off of that corner-fed example?
The other thing to think about-maybe-is how to isolate the feed line from the element when fed for vertical polarization (on one of the sides). I guess you’d ideally want to pull that feed line away at a 90 degree angle from the side, otherwise I’d assume you’d get coupling between the feed and the radiator. If choked well just below the base of the rectangle (to isolate the CMC on rest of the feed line to your radio), I wonder how much that would throw off the pattern? I’m thinking that this hypothetically makes this otherwise mostly balanced antenna into a more unbalanced one. Just spitballing here 😊

[@timg5tm941]

Food for thought, thank you

[@timdbl7804]

Hi Tim, thanks for again doing the spade-work with modelling this one! 🙂 Interesting results. Which modelling software did you use? I am usually reluctant to run radiators close to the ground (unless I have to, or just want quick-and-easy NVIS) as I think that there may be caveats as to whether my EZNEC programme assesses ground-coupling losses properly.

[@timg5tm941]

MMANA-GAL Tim

[@adyg6ad73]

Horses for courses. I guess it depends on your expectations for distance where you feed the horse (I mean antenna)

[@timg5tm941]

Agree mate

[@LB0FI]

Tim, we need to talk! I am looking into putting up a loop at home, but I suck at modeling…

[@timg5tm941]

Email me your dimensions/ideas

[@LB0FI]

@@timg5tm941 Email sent. Thanks!

[@richm2835]

Would you use something like a 4:1 balun at the feed and Is it resonant on 40m and the harmonics ?

[@timg5tm941]

Yes you can use 4:1 and it should be harmonically resonant too