ADS-B DIY Antenna

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jmaurin

New Member
Well, I made my franklin antenna and finished my system. Believe or not, my position reports grow from about 110/5min to 320/5min on FlightAware! My range still the same, but I use to see about 12 and max 15 aircrafts at same time on my radar. Now, I see about 25 all the time and I got 33 last night!

I don't know if I can post links here (sorry If I can't, please some moderator remove this message), but if I can, this is the link to my project and reports: https://www.jonis.com.br/2015/08/17/raspberry-pi-2-para-recepcao-de-satelites-e-ads-b/

In the top-menu there's link to my current radar (ADS-B Ao Vivo) and if you don't speak portuguese, just use google translator at top. Also, I've build an webpage to show all loged flights from my receiver (Log ADS-B at menu).

This antenna is proving to be awesome!
 

trigger

Member
@jmaurin:

Great project. Well done for getting the collinear to work.

Do you find that you lose some reception when it rains? My collinear gets water between the stubs and changes the antenna characteristics.
 

ab cd

Senior Member
Today I made a new 6-element CoCo. I put it to test WITHOUT amplifier and 12ft/ 4m piece of RG6 coax between CoCo and DVB-T USB Dongle + RPi combo. As usual results were poor (see Image 1 of 3).

I then inserted a capacitor (1.5 pF ) and a piece of coax (length = 0.85 x 1/2 wavelength) between feed cable & CoCo, bringing it's Impedance down, and thereby improving its SWR. The performace increased considerably (see Image 2 of 3).

I found the length of coax piece & value of capacitor by trial & error, and a few trials only. If I would have tried more lengths & capacitors, I might have got even better results. The rule of thumb I use is that coax piece's optimum length is somewhere between 0.75 to 0.9 of 1/2 wavelength element of CoCo, & the capacitor 's optimum value lies somewhere between 1 pF and 3 pF.

Please see Image 3 of 3 showing the impedance matching arrangement.

The two screenshots of dump1090's gmap were taken with a difference of 2 minutes only, the time taken to insert/remove the capacitor.

IMAGE 1 of 3- dump1090 gmap, NO Impedance Matching, NO Amplifier




IMAGE 2 of 3 - dump1090 gmap, WITH Impedance Matching, NO Amplifier




IMAGE 3 of 3 - Impedance Matching Arrangement

 
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toml

New Member
I used rg6 for my earlier collinear (10 elements). My last one was built from Rg141 with solid copper jacket on the outside Used the free version of Touchstone software and a directional coupler with a noise source to adjust swr to close to 1:1. my average aircraft count went from 30-40 to 80-90 and coverage went from approx. 150 nautical miles in my best direction with the rg6 to over 220 miles with the rg141 antenna. Are you aware if you use standard coax for the CoCo elements, the vinyl covering will significantly shield it from 1090 mhz RF? The vinyl heats up significantly in the microwave oven (~ 2.4 ghz).

Tom
 

kucengemok

Member
I used rg6 for my earlier collinear (10 elements). My last one was built from Rg141 with solid copper jacket on the outside Used the free version of Touchstone software and a directional coupler with a noise source to adjust swr to close to 1:1. my average aircraft count went from 30-40 to 80-90 and coverage went from approx. 150 nautical miles in my best direction with the rg6 to over 220 miles with the rg141 antenna. Are you aware if you use standard coax for the CoCo elements, the vinyl covering will significantly shield it from 1090 mhz RF? The vinyl heats up significantly in the microwave oven (~ 2.4 ghz).

Tom
got any photos?
 

airbus340

New Member
Now I have been building another cantenna and I am very satisfied with it so I think I finally found the one I will use. It´s built of a soup can and cut to 69 mm, an f-barrel connector and a piece of coax for the top. My dongle is hooked directly to the amplifier - 20cm coax - cantenna. Todays catch was 106 positions per flight, best I ever had. First I tried 68 mm top, then cut to 66 mm and after that I tried 86 mm. The 86 mm top gave me much better message rate than the 68 and 66 mm.
 

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ab cd

Senior Member
Now I have been building another cantenna and I am very satisfied with it so I think I finally found the one I will use. It´s built of a soup can and cut to 69 mm, an f-barrel connector and a piece of coax for the top. My dongle is hooked directly to the amplifier - 20cm coax - cantenna. Todays catch was 106 positions per flight, best I ever had. First I tried 68 mm top, then cut to 66 mm and after that I tried 86 mm. The 86 mm top gave me much better message rate than the 68 and 66 mm.
Great! Congratulations.

86mm whip is 5/8 of half wavelength, a very popular whip length. Good radiation pattern & Gain, but higher impedance & SWR than 4/8 of half wavelength ( = 1/4
wavelength).

What is diameter of soup can?
 
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airbus340

New Member
What is diameter of soup can?
The diamater of the can is 70 mm.

I am sure you will calculate this in your program, it will be really interesting to see the result. Can you please calculate with 86 mm can as well so we can see if that will be better.

Same minute I put this antenna to work I could see a dramatic increase of messages so I knew it would be a good antenna. I went to the store next morning and bought another can just to have a spare one. :D
 

ab cd

Senior Member
The diamater of the can is 70 mm.

I am sure you will calculate this in your program, it will be really interesting to see the result. Can you please calculate with 86 mm can as well so we can see if that will be better.

Same minute I put this antenna to work I could see a dramatic increase of messages so I knew it would be a good antenna. I went to the store next morning and bought another can just to have a spare one. :D
Thanks for information about soup can diameter.

OK, I will run two computer simulations of 70 mm diameter can, one with with 66 mm whip, other with 86 mm whip

Please note that:
(1) Standard Pepsi/Coke/Beer can has a diameter of 66mm, which is not much different from 70 mm diameter of your soup can. Is 70mm diameter, or is it radius of soup can?
(2) Computer simulation results always have some error, which in some case can be as high as 15%. Some cases of computer modelling have even given results which are utterly wrong. Therefore simulation results cannot be blindly accepted without verification by actually constructing & testing the model. I like your approach to verify by constructing & trying.
 

airbus340

New Member
Thanks, will be very interesting to see the result! I will most likely cut the spare can to 86 mm and try 86 on both ends.

Diameter is 70, so close to a coke can.
 

toml

New Member
got any photos?
I don't have photos but it follows the same design as the YouTube video where 1/2 wave rg6 sections are pressed together, except mine is soldered, using a small jig set up to line the pieces up for soldering. The copper outer shield is easy to solder to since the teflon dielectric does not melt easily. The bottom eight element lengths were calculated and assembled using the velocity factor and the top two element lengths were adjusted for lowest return loss (swr) of the total 10 elements by slight trimming. No special matching was used and I have a preamp near the antenna with a 41 meter length of rg6 to the receiver. Most people have problems with collinears because they don't take the care to cut the element lengths properly using some tuning technique and wind up with the antenna resonant more than 20 mhz from 1090 with very high swr. This is a serious ADS-B antenna and the best one I have used by far compared with my 1/4 wave GP, rg6 collinears and slim Jims /J poles.
 

ab cd

Senior Member
........Most people have problems with collinears because they don't take the care to cut the element lengths properly using some tuning technique and wind up with the antenna resonant more than 20 mhz from 1090 with very high swr. ........
The Capacitor insertion technique given in my post #3687 above is meant for exactly this type of situation.

By using this simple technique, the novice coco makers can improve their poorly cut & poor performing Coco to a reasonable performance level, and will not get frustrated, and will not have to throw their poorly made, poor performing RG6 CoCo in garbage :):D

Being cheap & very commonly available, the unbranded RG6 Coax is the ideal choice for a novice. Unfortunately the precise VF of unbranded one is unknown, but luckily a VF between 0.83 to 0.85 is a very close approximation.
 
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ab cd

Senior Member
The diamater of the can is 70 mm.

I am sure you will calculate this in your program, it will be really interesting to see the result. Can you please calculate with 86 mm can as well so we can see if that will be better.

Same minute I put this antenna to work I could see a dramatic increase of messages so I knew it would be a good antenna. I went to the store next morning and bought another can just to have a spare one. :D

Can 66 mm dia, 69 mm height
whip variable length


Cantenna-variable insulated whip-can 66 mm dia 69 mm height.PNG



Can 70 mm dia, 69 mm height
whip variable length

Cantenna-variable insulated whip-can 70 mm dia 69 mm height.PNG




Can 70 mm dia, 86 mm height
whip variable length


Cantenna-variable insulated whip-can 70 mm dia 86 mm height.PNG

 

airbus340

New Member
Thank you very much ab cd for the calculations! Unfornately I dont understand much, the calculations you made earlier in this thread with gain pattern and the swr and gain numbers written to it is much easier to understand for a non expert.

I can see that the swr curve on the left side of the 86mm top is much higher than the other whips, is that worse or better? But the gain on this one looks very flat instead, so hard to say whats best.

I am still using the 68mm can and 86mm top and yesterday I got the brilliant idea to try with the diplexer again. I tried it earlier with another antenna and it got 80% worse but with the cantenna it makes an noticeable improvement. My best ever is 399 planes in one day and it is soon 11 here and I already have 183 planes, so it looks promising.

Tonight I will cut my spare can to 86mm and see how it performs.
 

ab cd

Senior Member
....Unfornately I dont understand much, the calculations you made earlier in this thread with gain pattern and the swr and gain numbers written to it is much easier to understand for a non expert.
Ok, I will post gain & pattern for all combinations of cans & whips.

I can see that the swr curve on the left side of the 86mm top is much higher than the other whips, is that worse or better? But the gain on this one looks very flat instead, so hard to say whats best.
I have run simulation for different sizes of can, and varied whip length from 50 mm to 90 mm (X-axis), and plotted SWR vs whip length and Gain vs whip length. Desireable is minimum SWR and maximum horizontal Gain (Theta = 90 degrees).

Simulation shows minimum SWR with whip 66mm to 68mm for all sizes of cans. Gain (horizontal) remains fairly constant and does not vary much with whip length. However the horizontal gain varies with can dimensions and drops from 1.5 dB for 66mm can to 0.8 dB for 86 mm can.

I am still using the 68mm can and 86mm top and yesterday I got the brilliant idea to try with the diplexer again. I tried it earlier with another antenna and it got 80% worse but with the cantenna it makes an noticeable improvement. My best ever is 399 planes in one day and it is soon 11 here and I already have 183 planes, so it looks promising.
Air traffic this weekend rose sharply (tourist/vacation season?? ). Watch number of planes for few more days. Most likely the numbers will fluctuate considerably.

Tonight I will cut my spare can to 86mm and see how it performs.
This is the best way to find out: build & test a design. Simulation do help, but sometimes simulation results may differ considerably from experimental results.

Please do cut your spare can to 86 mm height and try with both 66mm & 86mm whip to find out how it performs.

Waiting for your test results.
 

ab cd

Senior Member

1 0f 4
Can dia = 66 mm
Can height = 69 mm
Whip = 66 mm, insulated
Cantenna-66 mm insulated whip-can 66 mm dia 69 mm height.PNG




2 of 4
Can dia = 70 mm
Can height = 69 mm
Whip = 66 mm, insulated
Cantenna-66mm insulated whip-can 70 mm dia 69 mm height.PNG



3 of 4
Can dia = 70 mm
Can height = 86 mm
Whip = 66 mm, insulated
Cantenna-66mm insulated whip-can 70 mm dia 86 mm height.PNG



4 of 4
Can dia = 70 mm
Can height = 86 mm
Whip = 86 mm, insulated
Cantenna-86mm insulated whip-can 70 mm dia 86 mm height.PNG
 
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