DIY 5.8Ghz Helical FPV Antennas w/ IBCrazy Wavetrap Match

[@RobertResearchRadios]

I sell a different design of helical antenna called the "Bestagon Helical Antenna" that addresses some of the design flaws of the one in this video including accessibility to the solder joints and the need for glue. See www.ebay.com/str/robertsresearchandradios/Antennas/_i.html?_storecat=3930616419 for more info. Notes/Errata: 1. The length of the feedline used does not account for the velocity factor of the RG-402. It should be .7 of the value stated in the video if you want a true 1 electrical wavelength long line. That said, the length is irrelevant to the return loss (VSWR) neglecting cable loss concerns. I feel 5cm is pretty ideal for orienting the antenna on my goggles. 2. The calculated size of the reflector may be slightly larger than stated (a few mm). The value from JCoppens is a supposedly minimum value, but these all have performed great regardless of what the calculator says, both in terms of radiation pattern and matching characteristics.

[@Sircleanfpv]

Thanks, going to build this before my next trip

[@neilfpv]

Amazing information Robert! I don't have much knowledge about radio frequency but I can follow instructions and build them. I want to build a helical antenna for my dji fpv goggles v2. Should I build a 5 turn or a 7 turn? What is the advantage of each one?

[@user-eq2ug7in7b]

Damn... Look at those prices!!! I miss the good ol FPV days 😢

[@alexbringhurst8881]

Thank you for the video and the explanation on how to make the antenna. I'm going to try a pair of them on my HDZero goggles. Incidentally, I noticed the sore on your right thumb joint. It looks just like the kind I would get when I rode dirt bikes. Is that how you got yours?

[@stylesuxx]

Yeah, cool tutorial :-)

[@gregor.potrebujes]

I'm having some questions... The calculator says that the total length of the wire must be 282 mm. If I try to make the antenna with the wire that long, I only get 4.5 turns. Your antenna has 5.25 turns, which is closer to 5, but the length of the wire is 340mm istead of 282mm from the calculator. I'm really confused what to do here :) I would really like to get the base frequency as close to 5.8Ghz as possible. I'd like to hear your suggestion :) And thank you for your effort!

[@RobertResearchRadios]

The length of wire is less critical than the coil diameter and the spacing between turns. The wavetrap match should work pretty ok for helicals having any number between 3 to 10 turns, if not more than that. The source of "truth" for the antenna made in this video is inputting the listed parameters into the open-scad script; whatever that spits out is what has worked for me. I'd just do whatever the open-scad program spits out after you put your frequency parameters into the jcoppens site.

[@ninjalemon_Squash]

IB be Crazy

[@RobertResearchRadios]

Video Aerial Systems makes some crazy antennas that's for sure.

[@Indonesia01ian]

Hi, I wanna build my antenna Is it that hard to make a good antenna for long range? (+10km) using 5.8G band I didnt have any back ground in Electrical/Signal. Is there any guide to make a helical antenna? For me, the factory made ORT antenna 12turn is so expensive ($50)

[@RobertResearchRadios]

If you have a 3d printer. Helical antennas are very easy to make. If not, it's a little bit harder but RC Model Reviews had a video from a number of years back before these became COTS items. kzbin.info/www/bejne/nISafn6PoLCBY6M

[@MrDrumhummer]

Hi, could you please help, what is the maximum possible length of transmission line? Or how to properly calculate it?

[@RobertResearchRadios]

It doesn't matter how long the line is for the scalar matching information assuming a lossless transmission line (VSWR or Return Loss which are mathematically equivalent). In reality, the line has loss, so shorter is better for less loss. If you're familiar with a Smith Chart, you'll know that adding lossless line length of the normalization characteristic impedance just rotates the point around the center without changing your VSWR. I believe there is something about this in my errata, but it should just be VF * wavelength = .7 * 5cm = 3.5cm if you really want a one wavelength line. Don't forget to account for your connector length if you go down that road. That would just be to keep the phase angle part of the impedance unchanged, so it's not really worth it to bother. Just use 5cm; it works fine.

[@MrDrumhummer]

@@RobertResearchRadios thank yli very much for explaining. Just one more thing. When you demonstrated calculator, you have not change wavelength so it remained as 0.23 (which is 1200 MHz wavelength) is it still OK, you have made 5.8 antenna with different wavelength?

[@RobertResearchRadios]

@@MrDrumhummer The frequency parameter defines the wavelength. I set it to 5800MHz as required in the video as shown at 1:19. The turn spacing ".23 wavelengths" figure you mention describes the spacing between helical turns as a fraction of the wavelength for the defined frequency, in this case 5800MHz. It should be .23*lambda for all frequencies or thereabouts really; I believe ideally it would be .25*lambda, but the velocity factor of copper wire isn't exactly 1.

[@Dreez]

So is the wavetrap just a piece of metal/copper? which is isolated on the bottom side, so it wont touch the reflector?

[@RobertResearchRadios]

The wavetrap is the little piece of metal attached to the coil 1/8 the way on the first turn away from the reflector. You can read more about it on the original RCForums threads with IB Crazy, the inventor of the match and owner of Video Aerial Systems.

[@jumpermacc6786]

@@RobertResearchRadios What does this thing again? i'm not shure i understand that... i have 2 DIY 7 Turn Helical on my DJI Goggles and they work fantastic. but i did not do this Wavetrap thingy... didnt even know this was required. I would like to understand what it does and if this is needed...

[@RobertResearchRadios]

The wavetrap matches the antenna input impedance closer to 50 ohms. It's really useful if you are transmitting with the antenna to increase power output, but you won't notice much difference on receive. The DJI digial system transmits from the goggles, so you may want to consider adding a match if the VSWR is > 2:1. Check my video on budget VSWR measurements at 5.8GHz for how to do that if you don't have the equipment and/or skills to measure it for your antennas already.

[@marvinlange5797]

Can a 6.8Ghz RHP Video antenna be used for Data ? IE wireless network

[@RobertResearchRadios]

I'll assume you meant 5.8GHz instead of 6.8, but yes. The antenna can used for 5.8GHz ISM band wifi as well.

[@marvinlange5797]

@@RobertResearchRadios Yes Sorry for the Typo and Thanks you are first one of 10 people to answer that question

[@bwasfpv]

can i use this to my dji goggles?

[@RobertResearchRadios]

Yes, but you should use 4 of them. Also, I heard something about timing in the array and protocol limiting the range more than signal strength after a certain point. I you're trying to run them at the lower power level though and still get great reception these antennas may be worthwhile for the DJI goggles.

[@nanamigaming3434]

I admire your guts for trying to sell this. The solder is too poor. And if you seal it with glue, you can't maintain it or locate the failure. The design is wrong from the start. It's useless. I guess it works for elegant experiments in a polite room, but in the field, I'm not so sure.

[@RobertResearchRadios]

I don't believe it takes guts to sell something that works. This is after all, a hobby project under my side business LLC, but to be fair, I don't sell the design in this video anymore. I did a limited run while I was developing my own design that addresses some of the points you raise. The helical antennas I sell now are a called the "Bestagon Helical Antenna", a print in place variant with a CNC'd reflector that leaves the solder joints exposed for repair and maintenance and avoids any need for glue. See my store page antennas section for pictures: www.ebay.com/str/robertsresearchandradios/Antennas/_i.html?_storecat=3930616419 I'm not sure why you feel "The solder is too poor." It's proven in the field through use on my goggles for over a year to be durable enough to frequently reposition in hot and cold conditions, and the reception has been excellent over the duration, so the RF connection is not in question either. I've never had this design fail in the field on me, but I'm not throwing my FPV goggles on the ground all the time, so I won't claim the ones in the video are the most durable thing in the world, just good enough for my purposes. Certainly covering the solder joint and requiring glue as with this design are major drawbacks, ones addressed with my design changes as stated earlier. You should actually visit my Ebay store page to look at the new design. If you still want to criticize my soldering like people criticize welds, I'm not going to stop you, but if it works well enough for me, it's likely good enough for others as well. There are a few criticisms of my redesign that I can think of including difficulty in soldering the coax shield to the reflecting side of the reflector and that it returns to having a hole in the center of the reflector as with thingiverse variants that use a screw to secure the coil guide structure. I haven't noticed any significant effects on performance with these changes though. I will also note, I don't currently wavetrap match 5.8 GHz helicals for sale because they're receive only for FPV use, so there could be something to complain about there if you wanted to use them for wifi or the DJI goggles. I'm working on developing an easier to install taper match to replace the wavetrap with at the expense of bandwidth to add to the design in the future. This is what I intend to use for other frequencies as the Bestagon Helical Antennas will be releasing in other frequency bands for amateur satcom applications including dish feeds and low gain antennas for applications such as hydrogen line astronomy, EME (reception only possibly), INMARSAT EGC Broadcast and NOAA HRPT reception, etc. I will also likely be switching to PETG for UV resistance in dish feeds meant to stay outside. Stay tuned to the channel for more updates.