Yeah, I did that a little bit for trimming them to the calculator’s calculated length. I was originally going to use brass rods but didn’t have enough to complete an antenna with what I had left, they would be way more stiff and resistant to being bent. Also good note on the angles on my radials, I’ll have to look into it when building another slightly more durable one, something I can take with without risking breaking it. In regards to tuning and placement, I don’t think I’ll have a permanent mount for it, so I’ll probably be ok not having it being spot on, but I’ll keep this in mind if I do set up a permanent station at the house, perhaps to interface with a raspberry pi.
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Well, I built another one. This one is a little bit more durable, and with a range test I was able to reach a little further than before. It was no scientific test by any means, but I was able to send and receive messages further away through more buildings. It would sometimes not get the acknowledgement packet, but would still be received on the other end. I’m still using the rather crudely built antenna on my radio at the house, but soon hope to rebuild it to be a bit better at least.
Also I do want to experiment with higher powered modules in the future, perhaps design a custom board to accommodate it… ahh, exciting thoughts.
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Dang! Looking really good! I like how you used a telescopic whip to pass your ground and I’m presuming that you ran a wire down the center? Would be super interesing to see what your velocity factor is and how the crude coax works! 
Actually thats just a coax cable I pulled from a security system we were removing that had a gsm module in it. There’s just a skewer taped to the side so the cable isn’t flopping about.
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Super nice your Antennas, in order to understand your radiation pattern, do you have a picture or better a description on your antenna “Test Bench”, What distance you measure? What is your antenna (s2) counter part? Thanks in advance!
I have a question regarding the construction of antennas in general, and unfortunately I don’t think i’m getting the right searches into google, as I can’t really seem to find anything. I’m thinking about using a small amount of epoxy of sorts to help make my antennas a little bit more durable, maybe weather resistant? I know that it’s going to affect the tune and stuff, but is it a good idea to do so, and by how much do you guys think it’ll affect it? (again, no analyzer to check… it’s one of the things i’ll have to invest in sometime in the near future.)
Also a quick edit, but I don’t mean to coat the entire antenna, just the base where the elements are attached to, in an attempt to make them more secure.
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It looked like the telescopic antennas haha
I’d keep construction to solder and copper or the materials that you will be using in the antenna unless the materials are needed to keep the antenna in place and take shape. If you do use epoxy or other materials, yeah, it will affect the tune. Just make sure you give yourself 5-10% more length on your radiating element to tune it after you get it to how you want it. (If you have a ground element, like ground plane or dipole, do the same with those)
My designs of the 3-element Yagi antenna by @Der_Bear
The last one was made from bamboo skewers, is very easy to reproduce, and has very good performance.
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Hello friends! And again it’s antenna time!
Over the past half-year, work has been done to simulate and optimize several Yagi antenna designs. I tried to take into account many possibilities and nuances. The result of this work was the emergence of a basic structure of 3 Yagi elements. The power of the antennas was taken into account according to the radio engineering canons through the balun. It’s done right! For this design, a printed circuit board with a base for attaching extensions was developed. These extensions, depending on your tasks, allow you to build up from 4 to 8 Yagi elements. I have compiled the parameters of all the presented structures into a table. The sizes of all elements are also presented in the table. It will be easy for you to select the required number of elements for your task.
The presented models and designs are not “divine true”. Again, this is an attempt to find the optimum between the convenience of manufacturing, antenna parameters and your possible qualifications as a mechanical locksmith.
Also, I want to speculate a little theoretically why it is worth making Yagi antennas. This reasoning concerns the urban application of the node.
Among us there are radio amateurs and, probably, even professional communications operators or technical personnel of cellular operators. (I guess). The issues of using different antennas repeatedly come up and classic clichés from radio communications are often heard.
The canon of classical radio communication says that if the antenna is on the roof and sees everyone around, then a vertical collinear antenna or multistory dipoles are the best solution to ensure communication range. No one here argues with that! Classic! But, in the application to the mouse, there are several characteristic features where this rule is limitedly applicable.
Consider these features:
- The power of most devices is only 50 … 60mW.
- There are only 3 hops.
- Most of the people from the city broadcast from a window or balcony.
This means that it is desirable for us to shout not to everyone around, but to the powerful base of the repeater / key node. In the application of the fact that most urban subscribers broadcast mainly from the window, it is very desirable to concentrate the radiation in the direction “from the house” or, at least, to minimize the absorption of radiation by the house. I modeled the 3-el Yagi so that the maximum radiation would fall on the maximum possible sector in the window / balcony limitation, i.e. 180 deg. But, 180 degrees 3el does not know how, but in 130 degrees they managed to do it. With such an antenna, the radiation efficiency (the probability of communication with the nearest subscriber) turns out to be an order of magnitude better than the native stock antenna of the device. This works at the expense of better gain and good antenna beamforming. Next, we consider the case when the node is located among a large number of reinforced concrete buildings. With 3 Yagi elements, there MAY be unpredictable multipath propagation of the signal and a decrease in the radiation efficiency (communication probability) can drop dramatically (experience is required). In order to somehow compensate for multipath signal losses, we compress the antenna directional diagram even more and increase the gain - i.e. we make a multi-element antenna and select the direction where the signal will be reflected in order to reach the nearest node.
To build a network infrastructure, you just need a classic canonical approach - here I am 100% FOR: a good collinear antenna, a powerful node as close as possible to the antenna and the highest possible installation point. This is the perfect case. In practice, we have a slightly different situation. The people who have the ability to put powerful nodes live on the outskirts of the city, which means that the pie chart does not make sense yet. In my opinion, it makes sense to put 2 … 3 el Yagi in 4 floors and overlap the city with sectors.
Once again I want to emphasize - my reasoning is not the ultimate truth - it is “thinking out loud”.
Let’s go further …
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Construction 5.
This is again a three-element Yagi, but made on a printed circuit board with a canonical RF power supply and expansion to 4 … 8 elements.
Note: I do not have a 3D printer and master skills in mechanical work. Therefore, perhaps my phot looks like a pathetic homemade product on the kitchen table. Those who have high modern technologies can improve the construct. I call for cooperation!
The new PCB has holes for mounting on a balcony or other mechanical base (mast, railings, etc.). Additional holes are used for attaching expansion extensions. Unfortunately, I have not figured out how to do this at home. I suggest you use your imagination. But, the minimum for the basic application you get “out of the box” of the project.
The circuit board is made in the Sprint-Loyout 6 program (you can easily find this program on the Internet). The board is laid out for general use. If the Chinese masters decide to clone the antenna base board for 868 / 915MHz applications, then I do not mind.
The actual prototype of the antenna.
Photo of the printed circuit board from the program:
Antenna radiation pattern and gain.
Antenna parameters: VSWR, LogMag, Smith:
Photos of 5 and 6 element extension extensions that I tested:
In order for the antenna to have a high gain, it is necessary to increase the number of elements.
Comparison table of the parameters of antennas from a different number of elements:
Table of length and distance between elements:
Important NOTE1: the presented designs are “the average optimum and alternatives”, assembled as the convenience of locksmith mechanical work (almost all elements of directors are 145 / 150mm).
Important NOTE2: When assembling and tuning antennas, it is highly desirable to use a vector antenna characteristics analyzer. For example, such as NanoVNA V2 (Version V2 measures much better than V1 at 900MHz).
There is a possibility that after your antenna assembly, some parameters may change in frequency. This may be due, for example, to other parameters of the PCB at a frequency of 900 MHz than those that I have at hand. If you have such a case, then it is possible to move the elements a little 1 … 3mm on the sides. I made a special reserve for this. Also, there is a possibility that the length of the active element of the antenna will have to be shortened a little or, on the contrary, increased. The microwave frequency section is very capricious and is fraught with many unpredictable surprises, sometimes not pleasant ones. That is why I strongly recommend making antennas with the measuring device! If you want a truly high-quality antenna, this is important!
This data can be found in the models for the MMANA program. (all materials will be uploaded to github in the near future)
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Note 1:
When repeating the design, the main condition for high-quality tuning and operation of the antenna should be the absence of metal components between the antenna elements! If you are going to make a 3D construction for mounting on a printer, then make sure that your material does not contain graphite or metal powder!
Note 2:
Structural elements must be made strictly from tubes with a diameter of 4mm. They must be located strictly in the same plane (+/- 1mm tolerance). If you use pipes of a different diameter, then the parameters can deteriorate very much.
If you want other diameters of elements, but write here, I will make the correct model for your diameters.
Note 3.
You can safely repeat the design of the antenna and it will work without tuning. If you have a measuring device such as NanoVNA V2 or similar, then you can do the ideal tuning. To do this, you may only need to move the active element closer / further a couple of mm from its calculated value.
Depending on your technology for making the active element, you may need to adjust the length of the active element slightly. All this makes sense only if you have a SWR panorama measuring device.
Important NOTE 4: when using power and mechanical tools and soldering equipment, be sure to follow the safety rules !!!
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All related materials are uploaded to the github here:
Your design is much better than the standard calculations on ordinary antennas design. But in order to start tuning, I found out to trim the central dipol first. If this resonance frequency is slightly below the final 868MHz, the final trim is done by the distance to the elements I added later. So the smith diagram becomes a turn point to my final resonance and the reactance point could be trimmed to 50 Ohm. Is this a hint, not to start on the final 868MHz with the dipole? I found out your cable turn is essential for me, but I did 90 deg to your foto, same level with the dipole for better results.
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I’ll post the next revision. That one has a small problem that I need to solve for.
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OK. Thank you very much.
Nice to see some homebrew. I am missing the quad and bi-quad antenna (11-14dbi). *68Mhz is handable in size. For 434Mhz I am using a Comet GP with 9dbi. 73 de pa0ag
Hi there,
What would be the measurements for the 3 element 433Mhz Yagi if I used 2mm copper rod instead of the 4mm tubes? Getting the tubing is either difficult or quite expensive, and I’ve got lots of 2mm copper rod.
Regards, Nick