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The slot dipole with V cut outs like an batwing antenna, not as good for broadband application but a little more compact than the slot dipole and a good gainer. Here an example for a wifi antenna slot antenna with V 24-25.cst

Wow that works like charm, thank you.

You are a real master

then its necessary to analyze the structure and look which parameter is related to lamda and which is perhaps related to other factors. And yes you have to find a center frequency. For a single band antenna this is easy for such a multiband its much trial and error i think. For me its easier to re-optimize the design for another frequency range. For lower frequency's there should be better designs that are not so big, the only other range i can imagine is in the 5GHz region but there you not need such a wide bandwith. Attached you will find the cst file, feel free to recalculate it for another freq. range or to find the lambda depending parameters ;-) slot antenna 17-27-reflectors.cst

And additional a variant with directors. They harmonize good with the design but they give only a slight improvement.

An improved version of the slot dipole with wings. Good broadband behavior and good gain. 1.7 - 2.7 GHz with SWR <1.3, Gain from 2.1 - 2.5 GHz > 13 dBi

Another Option?:

Here you find the size without the horn:

Yes this was the picture i have in mind. Thanks for the hint

I made a Batwing with directors and the swr is quite good. I have to make an mount for a tripod than i will compare it to some antennas but not today ;-). The result is a little bit different to the calculation but everything is made by hand so not 100% correct. In the middle of the wifi band the swr is at 1.1 to 1.15 depending where the antenna is pointed to. Its interesting that the antenna is still usable from 1.9 to 2.9 GHz so if the range from 1.7 to 2.7 GHz is needed it could be recalculated for 2.2 GHz and would still have a good gain. As i mentioned before i used Aluminium tubes for the directors which works quite well and printed the holder with PETG. The rest is also Aluminium sheet (0.5mm) cut with a wallpaper knife for clean cuts and soldered on with the help of copper tape.

At the beginning CST looks very complicated, i first also needed some time to do something. At the beginning its useful to download a few projects and look into the history list how the antennas are modeled and what is all done. Later you will be able to make your own projects and play around. When you have an Nvidia card with cuda make sure you enable the use of this in the environment variables under windows, it will speed up the simulation.

I have a SAA2 NanoVNA which costs about 80 Euro but can only measure up to 3 GHz, if you want to measure up to 6GHz you have to spend about the double for it. I think such a VNA is the most basic tool to measure any antenna. It gives you the ability to correct the antenna that it works like it should.

If you realy want to try different designs than its worth to buy a nanovna, they are not so expensive anymore. 15 years ago when i try to make antennas i simply compared the signal i get from them from a external router. Better signal, better antenna. But with a vna you can measure if the antenna is good and you can compare different builds or even change some parts for adjustment. If you only want a cheap antenna that even works when the dimensions are not 100% perfect try to make a batwing antenna. They are so broadband that even a small mistake will not change that much that the antenna is useless. For the Haringtenna i think you have to find a can with exactly these dimensions to bring it to work.

"Making a narrowband antenna is not so difficult, but stretching the bandwidth to the maximum is much more interesting" Its always depending on the goal , you can have a narrow band with high gain or wide bandwidth with lower gain, i see both on my trials calculating the parameters. My goal this time was to get good gain only on the 2.4GHz Wifi band with a compromise about the two scenarios, but i will also make a version with maximal bandwidth like the original batwing. "make directors from a core of a copper cable for electrical wiring" I first calculated the design with solid rods and i see no difference by using tubes. In theory the big tubes should have a higher bandwidth like a thinner wire but i will try it out. "The directors holder can be made from a thin strip cut from galvanized steel, like the butwing itself, the directors can be soldered onto the holder simply and quickly" The idea is good, but i have no laser cutter to make everything out of steel sheets, my fist batwing was made of this cut with scissors which was terrible. So i changed to aluminium which is easier to work with. To solder on it i apply a patch of copper tape which works very well. For the director holder its more easy for me to print this part with my Ender 3, then all the dimensions are right and i have to simply press start . For the batwing itself i also showed that this works but sheet metal gives here more gain and better swr. Copper tape and 3D-Printed part are only a poor mans replacement for printed circuit board which has losses like the original ones. But the idea with the rivets is good, my fist plan was to print some holes in the structure of the holder and use screws from behind the reflector to hold it in place. But perhaps even a cable tie will work here. But first lets modify the design a little.

With the help of Harry36 and this post: https://www.lan23.ru/forum/node/321323 i changed the design of the maximum gain Batwing with directors and got a real good result by using 10mm tubes as a director. The gain can be up to 15dBi but then the bandwidth is limited. I choose a more robust option that even crocked hands will have a good result with this. When i have time i will try to make one of these. The holder for the tubes can be 3D printed and the rest is a simple batwing so not to hard to make. The footprint of this antenna is only 20cmx20cm so its not so big like a horn antenna or like the "wifi gun" designs which look cool but have limited bandwidth and are very long. batwing max gain with directors.cst

Typically the antennas are designed to be like in the pictures. When you change something, even a small detail, it can be that the antenna is not working properly anymore. The resonant frequency will shift or the antenna will be not resonant at all.

Updated version of the Biquad in a pot for 2.4 GHz, this time with a better impedance match over a wider frequency range and vswr starting at 1 ;-). But as mentioned before there are better designs out there. Parameters

This is indeed much simpler and more stable over a wide frequency range. The idea with the directors is also not bad, perhaps with this the reflector can be a little bit smaller.

You are right, its not perfect. But the first goal was reach 16 dBi. I will try to tune the design for a more stable range.

Biquat + Horn for 2.4 - 2.5 GHz & optimized for gain Size Impedance + Gain Parameters: File: Biquad 2-4ghz-double-reflector.cst

And another variant of Batwing antenna, this time optimized for maximal gain and only one small frequency region (2.4G Wifi). With this restriction you can realize 13dB gain with this antenna. So the Batwing design is very flexible, can be brought band, small band, dual band, 3D printed, gives high gain and is relative easy to manufacture. Gain: S11 + VSWR: Impedance: Dimensions: batwing max gain-endcalc.cst

Additional a scan over a wider freq range to look how broadband the antenna is, and yes its very broadband. Usable from 4.15 GHz to 6.8 GHz:

I have recalculated Admins 5 Ghz batwing (Page 8) for better SWR if somebody want to make one. I also found that the SWR could be improved if the leg is not touching the reflector, so i added a hole at this place to reduce contact which seems to work. From the calculations the antenna should perform and work very well: Gain: VSWR + S11: Dimensions (this thing is tiny ): Impedance:

I played around combining batwings together, look what happen when you combine 3 batwings, easy 15.5 dBi (only calculated to fit 2.44 GHz but can be also very broadband): Also interesting when you combine this bad boy with a second one into an 2 X 1 array (18 dBi): Impedance and size: When 15dbi is also ok the size of the reflector can be smaller. To squeeze out the last bit of gain cst calculated a bigger reflector. It is still calculated without any support to hold it up but i think the design has potential ;-).

Update about the 3D Batwing. I had to optimize the reflector also. Now the antenna gives also proper gain in the 5.2 GHz range as in the 2.4 GHz range. Attached the new dimensions and Results. Please keep in mind, this only works when 3d printed. A bare metal antenna will have other dimensions! Dimensions: Gain: SWR + Impedance: Dual Band Batwing.stl