@ Devonian
Hi Nigel !
Maximum Range
What is the Maximum Range I can Get?
LDF1-50 Antenna
http://ads-b.ca/LDF1-50/super-antenna/
http://ads-b.ca/antenna-collinear-F-CYYZ2/
Regards
abcd
Hi abcd,
Thanks for the link to the horizon site - pretty much accurate as per data I currently have and know from experience.
I will continue with my CoCo out of RG58 as it will give an indication of differences between various antennas and will be at least more like something that most would be able to build.
Nigel.
You will need an a soldering iron with quite some power to solder copper pipe, i just made a coco with 10mm copper pipe and lmr400 (for non adsb frequency) and with a decent metcal rework iron and that took about a minute to get the pipe hot enough for the solder to flow.
had to resort to a blow torch to solder the balun/decoupling sleeve (2 inch copper pipe) bits together and onto the pipe 
i also recommend some plumbers solder it tends to have more flux in it.
out of interest what wattage iron are you using?
As for technique hold small blob of solder on the pipe without touching the next section until the solder starts to flow on the pipe then move the tip of the iron to the center of the next section which should heat up quickly then as soon as thatās flowed your done. Hopefully that makes sense, if not i shall try to make pictures.
Also pay attention to G8JNJ posts about the balun/decoupling as that pretty much defines where your coax stops and aerial starts, on my recent one i soldered the balun on without any coax in it and made the the center pipe over long so it didnāt matter where the balun ended up and trimmed it afterwards. Where it joined to the coax cable i slid it down so about 50mm of coax braid went over the pipe and spot soldered that on and wrapped it tape to stop the braid from fraying.
for your effort a 22mm end fitting and a bit of pipe would be enough.
Its a shame your not closer to me, iām surrey hampshire border near the M3.
Is this the secret of success of Coco made of corrugated sheathed Andrew Heliax coax?
When Coco elements are cut to length = VF x 1/2 wavelength:
The phasing elementās (core wire):
- Physical length = VF x 1/2 wavelength
- Electrical length = 1/2 wavelength - OK, optimum.
The radiating elementās (outer surface of the shield):
Physical length = VF x 1/2 wavelength
Electrical length = Physical length = VF x 1/2 wavelength - NOT OK, optimum is 1/2 wavelength.
This can be overcome by using air insulated elements (vf = 1).
Incidently in a currogated sheathed coax, the current on the sheath has to travel along the curved surface of sheath which is a longer path than if the sheath was plain, compensatig for shortfall caused by cutting short by a factor of VF.
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Soldering iron is definitely too low wattage as I use it for soldering up the odd bit of prototyping. I do have some plumbers flux. Iāll pop into my local electrical retailers tomorrow and pick up a better soldering iron.
Was digging through some of my old posts. The specs on my antenna and cable:
Coax is Coleman Cable (CCI) 92041 with a VF of .81 (RG-6 QUAD SHIELDED COAXIAL CABLE WITH TWO FOILS PLUS 40% AND 60% ALUMINUM BRAIDS). Can be found in most Home Depot or Lowes stores here in the CONUS.
Have tested various segment lengths between 116 and 111 mm and my best results were with 112.4mm segments.
Have only built and tested 8 segment 1090-COCOs. (should play with other counts)
Also built a UAT-978 COCO and had good results with it.
Cheers!
LitterBug
What segment length you used for UAT COCO? I tried to build 4 UAT COCOs and all of them performed worth then 4 legged spider 
My first CoCo - an 8 segment from RG8 coax with 1/4 wave top section āwhipā and bottom section ābalunā section has also proved to be no more efficient than my homebrewed 1/4 wave ground plane (spider) antenna.
I now have some Heliax and will attempt another CoCo - undecided if it will be 4 sections or 8.
At least the Heliax is nice and rigid and I will cut each section overly long and then machine them to the correct length on my lathe.
After some further reading, if the 1/2 wave coax elements are cut on the short side (even by a couple of percent), then the radiation pattern has a ādownturnā - that is, itās main lobes are below the horizon. I wonder if that is a possible reason that these CoCoās seem to be so difficult to get right for ADS-B use?
A lot of Amateur radio repeaters make use of this ādownturn featureā as often the repeater is located on some high hill and the users are below the repeater antenna. A lot of the designs are based around these repeater antenna designs.
Maybe we need to make sure we donāt cut the elements on the short side and make them absolutely perfect or err slightly on the long side? Even a couple of percent is enough to change the radiation pattern of this antenna and although we are not transmitting, the antenna needs to be as good as an antenna for transmitting so as to maintain the best radiation pattern as it also affects how it works as a receiving antenna.
I have no means of measuring VSWR at these (microwave) frequencies, but there is a useful article here that shows how a dongle can be used to measure SWR with a couple of extra components.
rtl-sdr.com/rtl-sdr-tutorial ā¦ se-source/
(scroll halfway down for SWR measurements).
I have a NooElec upconverter and might add the components to the noise bridge and Iām pretty sure I have a coupler somewhere thatās good to 10GHz.
Time is my enemy at the moment!
Nigel.
With the cable Iām using, the standard formula for calculating segment length is almost dead on for my testing at 1090. So I used the standard formula to come up with the length and rounded it up to the closest mm.
(Speed * Half wave / Frequency * Velocity factor = Segment Length)
300,000 *.5 / 978 *.82 = 125.7668711656442
I built 8 segments @ 126mm for 978. Performs much better for 978 than my 1090 does. (as should be expected)
Cheers!
LitterBug
(slip fit as outlined @ balarad.net/ )
I do NOT terminate with a resistor or short my COCOs at the top.
Iāve had little success with various coax collinear attempts, including regular coax and also Andrew Heliax which just didnāt pan out in practice.
Here is another potentially easier way of creating collinear antennaāsā¦
ads-b-flight-tracking-f21/a-new-way-of-making-stripline-antenna-s-t36677.html
Iāll try applying some of the feed/matching suggestions outlined in this thread to see if it improves my initial build, which looks quite promising.
Nigel.
@Nigel:
Have you tried a non-conventional wire collinear, the Franklin-Spider?
It is actually a 1/4 wavelength groundplane (Spider) antenna, modified by adding an additional element at top of 1/4 wavelength whip. The additional element is a 1/4 wavelength hairpin (stub), on top of which is a 1/2 wavelength vertical element. Please see this post for simulation results & drawing:
Click here: My post #2601 dated Apr 7, 2015, in Planefinder Forum (In this post, click on thumbnails of Simulation screenshots to see full size images)
It had mixed results. It gave better results than 1/4 wave Spider to caius & xforce30164, both indoor installation, but gave poorer results than 1/4 wavelength Spider to jepolch (outdoor installation) and abcd567 (me) (indoor installation).
Later, I managed to improve it by adding an impedance matching network - I cut the feed coax at (0.85 x 1/2 wavelength x VF) from feed point, inserted a 3pF capacitor in series with core wire, and joined the cut shields so that it remained continuous.
abcd
The key factor in my COCO success is the Disco ball at the top of my antenna as seen in my avatarā¦
Cheers!
Litterbug
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Hello Friends
Could someone tell me how long must each element bee if i use RG6 to do the elements and how much elements i have to do so that the antenna works fine and if i have to use a resistor at the top or is it no necessary?
Link me a ready project if you have some build with RG6.
Thanks
If you read these and many other articles on the internet, most have failed to make an adequately performing CoCo antenna with proven advantages over a standard 1/4 wave ground plane (spider).
Build yourself a quarter wave ground plane first and record the results you get from it over at least one week.
Without a āreferenceā antenna, you wonāt know if the next antenna you build that claims high gain is really working better or not.
Nigel
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This is a good place to start: balarad.net/
And this thread has excellent suggestions: ads-b-flight-tracking-f21/built-my-first-antenna-and-doubled-my-coverage-t19517.html?hilit=doubled%20my
The velocity factor varies a little between manufacturers and types . It will likely be around 0.82. Experimenting with small adjustments in segment length may improve efficiency.
The graph at this site illustrates the effect of additional elements. w8ji.com/stacking_broadside_collinear.htm
I would suggest you leave the antenna āopenā at the top.
As you assemble the elements, check the continuity between elements to be sure you do not have any āshort circuitsā caused by stray shielding wire touching the inner conductor.
A little patience building and you will have an excellent coaxial collinear antenna.
(1) I fully agree with views of Devonian (Nigel). You should fist make a 1/4 wave groundplane antenna and establish your system by running it for at least few days (or better few weeks), before attempting to make a Coco.
Please see this thread for how to make a 1/4 wavelength groundplane antenna (Spider or Cantenna):
Three Easy DIY Antennas for Beginners
(2) One of the most important thing in making a Coco is to accurately know the Velocity Factor (VF) of the coax used for making the Coco. This can be achieved by using a Coax of known brand & model whose Specs or Data Sheet is avaiilable on internet, from which you can find exact value of VF.
Once you know VF, the length of element is simply 138 mm x VF. For example if your RG6 coax has a VF of 0.85, then its element length will be 138 x 0.85 = 117 mm.
Hello and first of all thank you for your suggestions.
I am already testing an antenna, the vertical antenna that came with the FlightFeeder.
Building an antenna will be no problem and i like to try out different types, i am Ham Radio Operator thats why i like to experiment with this things.
I will order some connectors so i can try out both antennas, first i will try the collinear and then a GP.
Thanks for your help.
I started with 116mm segments for a proof of concept following the instructions at https://www.balarad.net/ After having great results compared to a simple ground plane, I built a second antenna and feeder and started tweaking the length 1mm at a time. Having two identical feeders from the same location made it easy to tell if the results were better or worse almost instantly by comparing plane counts, message rates, and range. If the results got better, I would shorten the other antenna to match and make sure the results were comparable. Eventually the results got worse (111mm) and I knew I was in the ballpark of optimal length for my setup. Using that method got me dialed in very close to the optimal length based on the VF for my cable. (112.4mm) Since then, I have played around with amplifiers and filters and have a setup that has been repeatable to build. Currently running two feeders 20 miles apart with nearly identical configuration. Tree cover, height above ground, feed line length, and geographical differences being the largest difference in config.
Current config at both sites:
8x112mm coco ā short feed line ā Paladin 20db Satellite amp ā Feedline (20ā on one 60ā on other) ā Ground block ā 10ā feed line ā DirectTV power inserter (21V) ā 3ā feedline ā R820T2 Dongle ā RPi2
I also had to tweak the gain setting on the dongle one step at a time to get the āoptimalā setting for each site. Too high of a gain setting will provide horrible results. One tick in gain level can have a drastic impact on the results.
Feeder 1 (Would like to get 20ā higher to clear tree line.)
38.6db gain, under tree cover, 15ā above ground
http://flightaware.com/adsb/stats/user/LitterBug#stats-5696
Feeder 2 (need to test with antenna mounted on opposite side of tower)
25.4db gain, on Ham tower, above trees, 50ā in air
http://flightaware.com/adsb/stats/user/LitterBug#stats-17370
Cheers!
LitterBug
Thank You LitterBug
I was doing a research on the cable I am using and it seems that the Velocity Factor of this one is 0.82.
So to have a good antenna the segments should be 1/2 wave length x 0.82 this would give the optimal element length.
In my case that would be 112.75mm.
EDIT:
Can someody tell me how i can fix the antenna to the mast ? Think about that the antenna is closed in a plastic tube, i will post some pictures soon.
I am just about to build my first CoCo. I am not sure which coax-cable I should buy. I have the choice of coax cable (RG6, 75Ī©) with 65dB, 90dB or 120dB. Does it matter how many db the cable has? Which one should I prefer?
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