Відео

Great job Denny!

Hi, I was very disappointed by a 80-meter band mag loop antenna that I built. Previously I had a non-resonant 20 ft legs delta antenna for reception. It was working OK and I thought that a small-tuned-loop would be possible for the 80-meter band local net. So, I spent six months assembling a remotely-operated-vacuum-capacitor and a rack to mount it on the roof of the house. When I finally compared its performance to a simple horizontal dipole antenna, I just wanted to to scrap the whole project... I tried a two-turns-loop of 5 foot diameter in both horizontal and vertical planes and also one-turn-8-fooot-diameter loop of the same 3/4 inch copper pipe in both planes. The 100 to 399 picofarads capacitor could tune properly the antenna to 3.8 MHz so I had a direct comparison with my dipole antenna. Total failure! It was impossible to hear my local network. Also, I could not reach 7 MHz and up, unless I make major modifications. That was the major surprise: they are not effective at low frequencies but they can not be tuned at high frequencies. Ahhh! Sad. You should also mention that the narrow band width (20 KHz) of the antenna makes tuning a little bit more critical because you usually do not want to stay on the frequency as you tune your antenna. For that I recommend the noise source and the bridge that makes you hear the noise reflected by your antenna and a chopper. Using this little gadget makes the tuning totally PASSIVE using your receiver only. It is available commercially, I just don't want to mention the supplier's name here. Best wishes.

I made a square no. 8 loop that works well, big area, great for indoors it’s narrow and tall (2/1), for 80m band only 2mm*40mm* 1500mm eight lengths shaping a number 8 with fix value capacitors in the Center and a variable motorised cap for fine tuning over the band.

You organised a great net Ray. Many thanks. Kaz. G4OWW. ……..

KMAG

Yep. You figured it out.

Notebooklm had me fooled here at first btw :)

The idea of a global ptt network over cellular is awesome, but the ads I’ve seen for one or the other of these services is totally full of bogus ideas of being better than cellular for reliability, while relying on cellular data entirely.

can this be used for only recieving

Hello, I've ordered the parts needed to build one, except for the cheap android phone but that's going to be done. Once all the parts get here, I'll assemble the project. then test it. Looking forward to the build.

Very good educational video KF0MOE

Very good. I started building a similar loop. However, I used 50 mm PVC pipe and aluminium flashing on the outside. The aluminium flashing comes in different widths but in long roles. It is possible to cover the whole loop with no joins. The flashing can be held in place with zip ties or something similar. The flashing can be bent around the corners with care and some practice. The loop is potentially more durable and should handle high power. Drew VK4ZXI

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.

Absolutely HORRIBLE audio. Was he using an ancient 1983 mobile phone?

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

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.

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 ..

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

Geat presentation

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?

Closely watching all of my video Elmer's post. John is way influential

While aluminum has a significantly higher DC resistance than copper, it has a greater RF conduction depth for a given frequency than copper does, so it is nearly as conductive to RF as copper is.

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

Would like to see the layout or diagram of how the relay is wired up and how it connect to the antenna.

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

Seeing the foil tape on the window one got me wondering: could you use the foil tape on something like plywood to make a modular set of panels for a super-long antenna for a really long wavelength? If you could go back and forth 20 times over a metre, then that's a 20-metre slot on a 1m^2 panel. Spread it over two, and that's a 40m slot. If you've got 30m of fence around your property to lean these panels against (3 sides, times 10m each), that's 600m of potential slot length without going over the height of the fence. I'm not an amateur radio guy, though, so I'm an almost-complete novice on the subject. I just stumbled across this and found it interesting.

NW Arkansas - one of the beautiful parts of the world.

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.

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?

Thanks you for a fantastic tutorial, I'm wondering is the HF double delta slot can fed with home brew ladder line, from a shack based manual tuner? negating the requirement to have a tuner located at the base of the antenna. 73 Martin

👉You mentioned a vertical positioned slot antenna is horizontally polarized, take away or reduce the metal to the slot and it is basically it is a folded dipole, but a horizontal folded dipole is horizontally polarized. What then exactly defines the polarization in the slot type antenna, please clarify my understanding?

An excellent and fascinating tutorial on slot antennas. I have plans to make a Hentenna for 2metres I had no idea it's a skeleton slot! I also have on the bench some copper tube that is going to be a cylindrical Alford Slot antenna for 23cms. I'm going to be sharing this presentation with some friends that will be interested in these designs. Best 73 de Mark GØUSL

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.

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.

On the subject of the Double DELTA Slot antenna; I see the obvious benefits of the collapsible and foldable compact size but I would really like to know if size were not so restricted and for a permanent application would there be any benefit in super sizing it? ie. Having something on the idea of a 16 to 24 foot cross section and whatever complimentary hight increase might coincide? Any guidance would be greatly appreciated! Thank you kindly Gary

How much could an 80 meter antenna be shortened if it was a helix antenna using cardboard tubing concrete forms?

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

i think (Not Sure) the Narrower Bandwidth = has Less interference = hence less Noise @ Rx Don't U think ?

i am Suhail HZ1si from Saudi Arabia Thank U for the demonstration many Antennas Manufacture speaks about Gain (Fine) ... but tell less about Radiation Angle ? (Shortened Dipole = 1.6 dBi) .... VS ... (J-Pole = 2.1 dBi) mmmm seems a trivial ... Not big deal .. i would consider it as connector or cable lose ... But here is the Big question >>> 1.6 dBi @ (What Radiation angle ??) ... Vs ... (J-Pole = 2.1 dBi @ 5 or less degrees radiation Angle)..

outstanding

Hey Genius .... Stop ... Don't reveal the Secret

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?

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

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

Loved it, loooved it, watched it three times! Mind blowing stuff, with QRP field application…. Thank you! de W7UDT

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

Actually Red is RF xmit Green is network xmit

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?

Is this technically a slot antenna?

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?