How to Design and Build a 70cm DIY Loop Antenna (EP37)

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This video is about building a loop antenna for the 70 centimeters amateur radio band. What I particularly like about this antenna is that it implements a bandpass and a powerful antenna at the same time. The principle of this antenna is actually very simple: A ring with the circumference of one wavelength is excited with its resonant frequency and thus acts as a filter and antenna at the same time. Since this type of loop antenna has a fairly high radiation impedance, a suitable matching network is needed for it, which is not easy to calculate. That's why we at “electronics.unmessed” have developed a dimensioning tool based on EXCEL: it allows you to design such an antenna for different materials and for an arbitrary frequency band.
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0:00 Teaser - Resonant Loop
0:23 Advantage of the Loop
1:10 Matching
2:00 Materials
2:45 Calculating the Layout
9:33 Antenna Assembled
10:30 Playing with Tolerances
11:40 Reflection Measurement
14:03 Insights & Next Steps
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Пікірлер: 10

@stirlingengr 8 ай бұрын

Is the spreadsheet available for download somewhere? I would like to have some students make some of these loop antennas for a radio direction finding activity. Your method is very attractive.

@electronics.unmessed 8 ай бұрын

Thanks for your comment! This is a great idea for your students! There is a lot more about this antenna to be found on the channel: working principle explained, power rating, NEC simulations, measurements etc. You can also click the link in the top right corner to find the other videos on the topic. Supplementary material like EXCEL tool, plans, etc is always found in the download section under the video. Looking forward to get your feedback ..

@stirlingengr 8 ай бұрын

@@electronics.unmessed Your github repo for EP37 only has a pdf of one design. I don't find the spreadsheet anywhere. Am I looking in the wrong place? Thanks again.

@electronics.unmessed 8 ай бұрын

That's right! Please check out my PLAYLIST "Antennas & Wave .." The EXCEL is under the video "Antenna Design based on ...! kzfaq.info/get/bejne/rJiadbuWnsjZhY0.htmlsi=gm7xXSqbZ5ePAq4p

@siddharth4662 9 ай бұрын

This is an excellent tutorial! :-) I just loved it. Would it be possible to ask you some queries directly!

@electronics.unmessed 9 ай бұрын

Thank you very much for your comment! Sure, you can either place your questions here in the comments or on my e-mail which is given in the channel information.

@migelsanders4956 Жыл бұрын

👍🙂

@electronics.unmessed Жыл бұрын

Glad you like it😀

@dennisgarber 6 ай бұрын

I am thinking, for the purpose of looking better and better reception, of building a triple loop version, mounted on a circle rather than the rectangle, with a circular reflector. The color of it matters too. The goal needs to be to make the homeowner association happy, as well as keep the artistic wives happy. This tri loop design would not look as ugly, as it would be reminiscent of wreaths and the familiar Olympic logo. I would lean towards copper because of its color over the years. I am not sure about getting an acceptable color for the structural circular wreath for mounting or reflector. The best liquid Paints have a maximum color life span of 7 years, which is too short for something like this which needs an outdoor lifespan of 30-50 years to make it worth the time and spark interest and excitement. Even a factory roof paint might only last 20 years. . Ai, and several sources, keeps telling me I need a capacitor. I have never once seen a cap on a loop TV antenna. I would add an odd multiple of channel 26 half wavelength, which is smack dab in the middle of the ufh and the vhf band. Odd multiples, or 1.5x,have been found to have a 6db stronger signal than a half wavelength. This is likely why 77 cm brought to life channel 8 and up to channel 24 in my house, without any uhf. My old 2004 balun had separate uhf and Vhf inputs, yet connecting the 77 cm wire to the vhf side brought in most of the available uhf, at least on half of the uhf band, just using the vhf side of the balun. I added a single wire cut to channel 26 and it brought in all the missing stations below 26 (or longer frequencies). Interestingly, I was able to get the missing high uhf by simply putting a high uhf wire at a 90° from the vhf wire at 2-4" distance. It must be inducing a current in the vhf wire... Technically, in my understanding the perpendicular ac electric current would induce a perpendicular magnetic, which must be pulling the electrons of the larger wire back and forth and creating current. Anyway, my question would be whether or not there is better balun technology nowadays than the separate uhf and Vhf inputs. Or is it better to separate them. Also I would think 91 cm just barely big enough to squeeze channel 15 through and a longer wire needed. Now, I understand that emf travels at 97% of the speed of light through copper, which means that we take the half-wavelength and will need to calculate 3% lower. In steel it might be 5% slower. However, this would not apply to a loop which is catching the magnetic via the air space in the inside, so a wavelength should be a wavelength. At 470 mhz, the beginning of the uhf, we get 32 cm, which requires more wire than 91 cm.

@electronics.unmessed 6 ай бұрын

Thank you for your extensive description and your interest in my videos! And don't hesitate to ask further questions. If you want to use this antenna for TV reception, which I understand from your comments, then you should keep in mind that the antenna is narrowband and therefore does not cover the entire television band. Otherwise your thoughts are all correct, I think. By the way, I like the cool idea of building a visually beautiful antenna! I can't really answer the balun question. An active element could of course be better for the purpose, because the aim is to lose as little signal strength as possible. I'm curious to see how your project continues. I think other people would be interested in this too. Maybe you would like to report about it here from time to time?