Making a 1090MHz CoCo Antenna for ADSB

[@travvler5045]

This video worked great for me. I'm picking up planes 70+ miles around me, which probably isn't great, but since my place is backed up against a forest with low LOS I'd say its pretty good.

[@LifeAtTerminalVelocity]

Glad it worked out!

[@grumpy_ken]

really cool build, this is my first time seeing one of these antennas- I'll give it a try.

[@LifeAtTerminalVelocity]

They are easy and cheap to build. Make one and take it for a spin.

[@grumpy_ken]

@@LifeAtTerminalVelocity so I made one, testing as I went, and it only performed about half as well as the simple ground plane antenna I use. just testing on my patio I only tracked around 30 aircraft with the colinear and then it jumped to 60 with the ground plane. maybe I did something wrong? I'll make another one when I get the chance. one thing about ground planes is that they have a great takeoff angle and view of the horizon for this kind of stuff

[@LifeAtTerminalVelocity]

@@grumpy_ken Not sure what to tell you on that account. I can tell you that the two I have permanently installed do really well and better than the ground plane I had before. It might depend on build and location of deployment.

[@grumpy_ken]

@@LifeAtTerminalVelocity yeah definitely. I probably messed something up, I'm going to try again some day I'm feeling patient- I want that gain lol

[@temporarilyoffline]

That's a good looking antenna, and 4x improvement is nice!

[@LifeAtTerminalVelocity]

Thanks TO!

[@Swede_4_TRMP]

Greetings from Sweden! You, Sir, just got yourself a new subscriber 🎉

[@LifeAtTerminalVelocity]

Tack så mycket, jag hoppas att du gillar mina videor.

[@26TM205]

I just used plastic shirt buttons between each element works perfectly. along with heat shrink sleeving 👍

[@LifeAtTerminalVelocity]

That's a great idea!

[@HACKPHILES]

Can you explain more?

[@26TM205]

@@HACKPHILES the shirt buttons have the inner core passed through the holes. they stop the outer shields shorting. So one button is trapped between the sections of the coax pieces. ensuring no short can occur. use a button instead of electrical tape. HTH

[@EdyBraun]

Great tutorial! I just started on my CoCo antenna build and will follow your instructions, as I have had the RTL-SDR v3 for a while and recently downloaded the software to pick up some ADS-B signals in my area (which worked but not great)! The calculator you linked suggests using 1/4 wave segments at each end, even if you use 1/2 wave segments. I found my coax is BELDEN-T F9116 DuraBond II Series 6 which I found has a velocity factor (Nominal Velocity of Propagation (VP) [%]) of 83% in the spec sheet. The calculator tells me for 1090 Mhz with VF = 0.83, I should be using 114.14 mm lengths for 1/2 wave and 57.07 mm for 1/4 wave. So should I be using 6 segments of 114mm, and then have the 2 ends each at 1/4 wave (57mm)? The 1/4 wave segment at one end would just terminate with the RG6 F Type screw-on connector that's already on the cable, and I would plug that into my adapter that converts it to the smaller SMA connector on my RTL-SDR. However, how do you terminate the free end of the antenna? Do you strip the last bit of copper core (just like for all the segments) and have it just sitting free in the air? This last length would need to be trimmed to match the 57mm length and not have any extra "overhang" because I wouldn't be using the extra to poke into the next segment (as you do with all the other segments to alternately link the cores to the shielding and vice versa).

[@LifeAtTerminalVelocity]

Glad it helped. I tried to terminate the antenna at the top with a resistor of the same value as the impedance of the coax and I didn't see any significant difference between the two. Your mileage may vary.

[@ronwolenski-n8wcr]

Just made it, works great!

[@LifeAtTerminalVelocity]

Great to hear!

[@alexclaros823]

Hola me queda duda que con el primer tramo de cable le cortas el trozo pequeño de conductor central ?

[@LionRoars918]

Very nice

[@LifeAtTerminalVelocity]

Thanks!

[@RICHIEWALLS]

Hi! I have a question, the elements at the outside of the main axis can be in different positions? Or the should be all aligned with the next one? Because I find it hard to made it so mine went all in different positions... Also, I put 13 elements but I think it should be even numbers only? Thank you!

[@LifeAtTerminalVelocity]

I don't know if you need to have even numbers exactly but I *think* that in theory that is the only way that the impedance balances out. You might consider adding a 75 Ohm or 50 Ohm resistor between the center and shield of the top segment and see if that improves things in the odd number segment scenario.

[@yv6eda]

Great video! Nice Coco!

[@LifeAtTerminalVelocity]

Thank you! I am hoping that the 2m version isn’t terribly difficult to manage.

[@WayneRigley]

HUMMMM.... i like it im going to build one but a few questions, my Pi is going to be in the top room and then the RG-6 into the attic into the bottom of the antenna, but not planning to have a coax connection at the bottom of the antenna, so i think i just start my 8 segments while inside the antenna housing.. and then you made an 8 seg .. does a 16 seg have any other benefits as in gain.. or is it not even worth it.. thanks for the video

[@LifeAtTerminalVelocity]

16 segments has more gain but for my purposes the little bit of extra gain wasn't worth building to. One way to tell - built it and test.

[@noobking5056]

@@LifeAtTerminalVelocity so I have around 250 segments will that improve the gain?

[@Banditt42]

@@noobking5056 I have 251 segments. Works great.

[@noobking5056]

@@Banditt42 size of each segment?

[@K0BJJ]

Hey Bud you could have used that little bit :P Just playing interesting build.

[@LifeAtTerminalVelocity]

Thanks! I did use it a little, it is in the video. :)

[@SimonShaws]

So.. velocity factor, this has me stumped. The vf is the speed of propagation in the core. But we're swapping to shield on and off where the vf is much closer to 1. So... what vf to use to get it more exactly on frequency?

[@LifeAtTerminalVelocity]

Excellent question! Keep in mind that I'm not an antenna theory expert and what I know about this design comes from what I have read when I was looking for a solution that was inexpensive. This is a set of stacked antenna sections on the same plane (Co-linear) made out of Coaxial cable (thus the moniker CoCo for Coaxial Co-linear). So the actual antenna segments are every other segment starting from the base. So if we number the segments sequentially the only real parts of the antenna are the odd number segments. We are using the shield of the even sections to transport the signal of the odd sections and the center conductor to transport the ground of the odd sections. Thus the velocity factor only matters in the sections that receive the signal. It took me a lot of reading to get to that point because I couldn't understand how the actual antenna worked given it theoretically is just one big continuous chunk of copper. Until you alternate the centers and shields. Wild ain't it? So use the vf of the coax you are using to build the antenna. It will work.

[@SimonShaws]

@LifeAtTerminalVelocity I'm dubious. I've built a few myself. Yes they work, but without some very expensive test gear it's impossible to tell how well they are working. Phasing issues could also arise with the differing vf. If we're not too fussed about being spot on, yes it's Ok. I've also seen multiple designs, with quarter wave stubs, quarter wave initial segments followed by half wave then topped with quarter wave. I may try modelling in AN-SOF but its a tricky one to build in a model.

[@LifeAtTerminalVelocity]

Not expensive at all to get the equipment to test it. A NanoVNA is $61 - amzn.to/3pOj3Dy

[@SimonShaws]

@LifeAtTerminalVelocity I have one. Won't measure gain though.

[@brendancooney9401]

Was a 146.5MHz antenna ever build, dont see it anywhere.

[@LifeAtTerminalVelocity]

I sure did and it works great. Never made a video about it because this video shows how to make the antenna. Didn't think duplicating the content wight a different length would serve a purpose.

[@brendancooney9401]

no nothing.

[@subaquaticsleepwalker7240]

Hmmm I have a rpi zero 2w I’m wondering if it will run this software?

[@LifeAtTerminalVelocity]

Oh it will! Take it for a spin, you will get hooked.

[@norvigosracing7083]

I am having difficulty about the elements size calculation as to which length to cut them. Because instead of a 70 Ohm i have a 50 Ohm coaxial cable but don't know the velocity factor of the coaxial cable i bought. It doesn't mention aything about it.

[@LifeAtTerminalVelocity]

I wish I could help you but without knowing the velocity factor you just have to guess. The alternative is to buy some cable who's velocity factor you know or can look up.

[@norvigosracing7083]

@@LifeAtTerminalVelocity I found a simlar cable like the one i have with same core material, insulation and shielding. I will use the velocity factor of that since it also has the same Ohms and pray for the best. Worst case i buy i new cable.

[@SimonShaws]

You should be able to google the vf from the cable data printed on the actual cable.

[@TI2GBB]

Did you build the antenna for 146.5mhz? I'm looking some info to build one for APRS freq, 144.390. 73s!

[@LifeAtTerminalVelocity]

I haven't built the antenna for 146.5 but the process would be the same as for 1090MHz. Just with different length elements. For 144.390MHz using standard 75Ohm RG-6 it would be 430.83 mm per segment. I would use at least 8 segments.

[@TI2GBB]

@@LifeAtTerminalVelocity I want to use for TX & RX, so I think it will be 50ohms coax on this case right?

[@LifeAtTerminalVelocity]

Yup. The length would be different because 50Ω Coax has a different velocity factor. You might also have to add a 50Ω resistor to the end for the SWR to come into where it needs to be.

[@TI2GBB]

@@LifeAtTerminalVelocity I will try to build it during this weekend, my only doubt is the topic about 50ohms resistor, is that like a stub for tune the antenna? thanks!

[@LifeAtTerminalVelocity]

That is my understanding of it but I have never put it to the test.

[@Trent28888]

Glue lined heatshrink on the joins would of been better

[@LifeAtTerminalVelocity]

No doubt, but since it needs to go inside a PVC pipe for support and use outdoors the electrical tape was sufficient for my needs.

[@SimonShaws]

You could probably fit the entire antenna in one big length of heatshrink for giggles.

[@n1rbd]

Any reason you used 75ohm instead of 50ohm? I didn't see any matching unit or transformer in your build. Did I miss something? Have you tried a 1090 bandpass filter? Looks like you're in a suburban area and was curious if you saw any difference. I'm looking at making one of those using some LMR-400 I have left over from my dual band antenna install and use N-connectors and LMR-400 all the way to the coax input panel at the house. Then some LMR-400 ultra flex to the radio using a 4" pigtail to make the N to SMA transition. That should give me minimal loss compared to most other cables. Your video definitely gave me some direction on where to go with this. Thanks!

[@LifeAtTerminalVelocity]

Hi Richard, I used 75Ohm Coax because it is perfectly fine for this application. I’m only receiving and not transmitting, the impedance match is not required and lets me make an antenna very cheaply. There is no matching unit or transformer as it isn’t necessary. I use the ADSBX Bandpass Filter, it is listed in the video that follows this one (Making an ADSB receiver). Your plan for LMR 400 is solid from what I can tell. Get your receiver up and running and have a blast with it.

[@hmchiaeth5317]

How to build antenna with 868mhz pro?

[@LifeAtTerminalVelocity]

You can head over to this link. Plug in the frequency and it will give you the length you need to cut each section. Assuming that your coax is RG6 your VF should be 83-86%. Coaxial Collinear Antenna Calculator - jeroen.steeman.org/Antenna/collinear-coax

[@WayneRigley]

@@LifeAtTerminalVelocity that link is dead

[@rogergrimsby5805]

It's working today 4/10/2022