ADS-B DIY Antenna

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ab cd

Senior Member
Just as well some people are determined so they can enlighten us.
My eyes glaze over at the mention of imaginary numbers o_O I've found a couple more videos on Youtube which I'll watch - assuming I stay awake.
Imaginary numbers are a mathematical phenomenon. The electrical quantities such as voltage, current, resistance, reactance etc are not imaginary, these are real quantities. However sinusudal wave behaviour fits exactly to imaginary number maths, as well as to vector maths (developed initially as mechanics of forces acting in different directions). Alternating current calculations therefore take advantage of already developed tools of vector maths and imaginary number maths.


In that case I won't make one as my CoCo also out-performs all the other antennas I've made.
Well I experiment to find out the "best antenna". There is always a possibilty to find a new or modified design which is better than the design which is currently the best. Sometimes apparently crazy ideas like Columbus' "Sailing West to reach East", can bring astonishing results.

Story of my best CoCo:
Following process repeated innumerable number of times over a period of 1½ years, till I hit the gold mine:

make > test > throw in garbage :(
 
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ab cd

Senior Member
Look what I caught on my receiver:
A crazy pilot taxiing under influence of alcohol?
No it is an airport maintenance vehicle fitted with ADS-B transponder! :D


Mantenance Vehicle at CYYZ.PNG
 
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trigger

Member
Amazing accuracy from the ADS-B transponder, decoder and mapping. I wish my sat nav was so accurate! I often seem to be driving in a field.
 

jmaurin

New Member
Uow! There are sooo many antennas that I'm lost.
What antenna do you think is the best for outdoor use and build? I'm thinking to build franklin co-linear with wire of 1.65mm. I'll use with an 1090 filter and LNA (homemade with PCB).

Tks!
 

ab cd

Senior Member
Uow! There are sooo many antennas that I'm lost.
What antenna do you think is the best for outdoor use and build? I'm thinking to build franklin co-linear with wire of 1.65mm. I'll use with an 1090 filter and LNA (homemade with PCB).

Tks!
First try two easy to make & reliable antennas:
(1) Spider 4 leg (if you feel it is difficult to solder) or 8 leg (if you feel it is not difficult to solder)
(2) Cantenna

After making these two easy & reliable antennas, attempt to make a Collinear - Franklin Collinear (hairpin/stub), or Coaxial Collinear (CoCo), or wire Collinear (whip with coil).

Remember, Collinears are very tricky, but very alluring also. These look simple & easy to make, but the problem shows up after making, when you try these. Often first-attempt Collinears are much inferior to what is claimed or expected.
 

ab cd

Senior Member
Tks!
Since I already have a system running, I'll try to build Franklin Collinear directly instead of spider or cantenna. I also have build this filter + amplifier:

Your filter+lna looks great!

Good luck with Franklin. Forum member @trigger: (Dave) has vast experience in making successful Franklin & successful CoCo. In case of difficulty, he may provide you valuable practical tips.
 
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bramj

Member
8 Elements Brass-Collinear performing well during Weather Alert

Screen Shot 2015-07-25 at 14.26.28.png
Screen Shot 2015-07-25 at 14.26.44.png



Plane's holding and go-around's

Screen Shot 2015-07-25 at 14.22.26.png




Screen Shot 2015-07-25 at 14.27.28.png



Screen Shot 2015-07-26 at 12.49.12.png
 
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ab cd

Senior Member
stratolaunch-largest-plane-1.jpg

The largest plane Stratolaunch, nicknamed “Roc” features two fuselages, six Pratt & Whitney jet engines, 28 landing gear wheels, and a whopping 385 foot wingspan.

If you were to put the center of this airplane on a football field, its wingtips would extend beyond the goalposts by about 15 feet on each side.

Those dimensions make it 65 feet wider than the legendary “Spruce Goose” H-4 Hercules, 95 feet wider than the spaceship-carrying Soviet Antonov An-225, and 123 feet wider than the modern Airbus A380. In fact, it is being constructed using pieces of two already quite large planes–a pair of disused Boeing 747s.
 

ab cd

Senior Member
With recent improvement in my antenna gain, I have started picking up planes on ground at Toronto CYYZ airport. The strange thing is that the Toronto airport is TOTALLY behind a large high rise building when viewed from my antenna location, my antenna is lower than the surrounding buildings, inside my apartment, and I dont see any way the microwaves can penetrate and cross the large high rise building with left-over signal strength above the threshold of the receiver. I think the only possibility is multiple reflections from glazed glasses of buildings nearby, as shown in attache sketch.


CYYZ Reflections.png
 
I am impressed with the quality of this forum !
I have been receiving flight data for 2 months now with a coaxial collinear antenna with 15 sections located under the roof . The antenna feeds an LNA board that in turn feeds a Nooelec R820T2 usb RTSL-SDR. I am receiving around 80K-90K flight reports per day (Flight Aware data).
Looking at your great drawings, comments and tests, I want to try new antenna designs. First some questions:
  1. Can I place the DC blocage (220 pici-farad) capacitor at the end of the collinear antenna instead of between the coax and the antenna ? From an RF point of view, it will terminate the antenna but will not short the DC feed to the LNA's
  2. I have a 3 way TV splitter with a power bypass port included . The labelled IN port is DC connected to one of the OUT port. The other 2 ports are DC isolated from the 2 previous ports. The idea being to connect my 18 volts DC to the out port connected to the IN port and the RTL-SDR to one of the other two OUT port. Do you think it will work OK ?
Once I try this I will try your Franklin antenna....sound too good to miss.
Thank you
Best regards (73 for the AM radio man)
 

ab cd

Senior Member
Welcome aboard Jean Yves Dionn.

I am happy to see someone from Canada (I am from Canada as well).

Can I place the DC blocage (220 pici-farad) capacitor at the end of the collinear antenna instead of between the coax and the antenna ? From an RF point of view, it will terminate the antenna but will not short the DC feed to the LNA's
If your Coaxial Collinear is already shorted at top, you can replace the solid short by a capacitor of 220 pF. If your Coaxial Collinear is open circuited, by shorting the top of antenna with a capcitor may deteriorate it's performance. Anyway unshorted antenna does not require a DC Blocking capacitor. You can check your antenna if it is shorted or open by continuity test using a multimeter or continuity tester connected between core and shield at feed point.

I have a 3 way TV splitter with a power bypass port included . The labelled IN port is DC connected to one of the OUT port. The other 2 ports are DC isolated from the 2 previous ports. The idea being to connect my 18 volts DC to the out port connected to the IN port and the RTL-SDR to one of the other two OUT port. Do you think it will work OK ?
Your TV Splitter with one port power passing and other power blocking may or may not work as power inserter. Also TV Splitters circuits are designed for frequencies below 850 Mhz, and may attenuate 1090 mhz to some extent. Better post a photo of the label to make clear how are connections inside.

Once I try this I will try your Franklin antenna....sound too good to miss.
Good luck! A word of caution: all Collinears are tricky, and have little tolerance to dimensional variations. Few mm error in DESIGN or few mm error in CONSTRUCTION can knock a Collinear from excellent to poor. Collinear category includes:

(1) Coaxial Collinear
(2) Franklin Collinear Dipole
(3) Wire Collinear (monopole multi section whip with coils inserted between sections, plus groundplane made of disc, radials, or sleeve).

Try Spider & Cantenna first. These are most reliable & easy to make antennas, with a 1/4 wavelength whip connected to core of feed coax, and a groundplane connected to shield of coax. These have:
(1) Large tolerance to dimensional errors, and are therefore good as DIY antennas.

(2) These are naturally resonant, i.e. have impedance about 75 ohms at operating frequency. This gives a decent SWR of less than 1.5 for 50 ohm & 75 ohm systems.

73, ab cd
 
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Thanks for your answer,
My antenna is currently open at the top......For my education, what is the reason for your design to be shorted at the end ?
Concerning the splitter that I have, the label says ''5-2400 Mhz ''. So it is for satellite receptor I guess ? I have tried to get info on internet : No luck
I have started this little project for fun....and fun it is: It got me going all over to understand ADS-B, antennas, PI, Debian etc. Learning is great for your mental health they say !

Will let you know,
Regards,
 

ab cd

Senior Member
My antenna is currently open at the top......For my education, what is the reason for your design to be shorted at the end ?
It is said that a half element (1/4 wavelength) shorted at top helps in bringing impedance closer to 75 ohm & improve SWR. Hoever I have tried both shorted and unshorted ones, and did not notice any difference. I have finally settelled for an 8 element unshorted CoCo, which is in my use for quiet some time.

Concerning the splitter that I have, the label says ''5-2400 Mhz ''. So it is for satellite receptor I guess ? I have tried to get info on internet : No luck
Can you please take a photo of your splitter & post it?

I have started this little project for fun....and fun it is: It got me going all over to understand ADS-B, antennas, PI, Debian etc. Learning is great for your mental health they say !
Most of us have started this project as hobby & for fun.

Will let you know
Will wait for your further inputs.

Meanwhile have a look at this thread also:

THREE EASY ANTENNAS FOR BEGINERS

You may like to build these for fun. If your antenna is indoor, then Cantenna is particularly easy as it does not require any special parts (SO239, PL259 or N connectors), and requires only a F-female to F-female barrel connector, which is very cheap and is readily available at Satellite/TV antenna shops, convenience stores, and Dollar Shops.

Cantenna also does not require any soldering.

Caution: take care not to injure you hands when cutting / handling the can, its cut edge is sharp. Better cut it longer and fold back extra length inside the can to make edge non sharp, or file the cut edge & apply adhesive tape over the cut edge/rim to cover sharp edge.
.
 
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Jose Morales

New Member
Hi everybody,
This is a very quality forum, i have a few antennas, one from FR24 (used by PF, FA and FR24), one for AIS and other for airband (dipole), how many cm or meters should be separated from each other?
 
The splitter is made by BZT the type is G687 or 673E. I have tested for DC continuity between the IN pin and the OUT pin linked by the red line and it is connected but there is no DC continuity with the other 2 OUT pins.
P1200975-001.JPG

 

ab cd

Senior Member
The splitter is made by BZT the type is G687 or 673E. I have tested for DC continuity between the IN pin and the OUT pin linked by the red line and it is connected but there is no DC continuity with the other 2 OUT pins.
View attachment 2288
The red line "Power Pass" not only passes DC, but also passes1090 MHz.
The RF impedance of DC Adapter is nearly Zero, while that of receiver is 75 ohms, therefore almost the entire 1090 MHz signal will be shorted through the DC Adaptor, leaving practically nothing to go to the Receiver. :mad::(. Just give it a try and you will find no or very little RF signal at the receiver.


The DC inserter does two things:
(1) Blocks DC to go to Receiver but allows RF 1090 MHz to pass un obstructed (a Capacitor in series blocks DC, but allows RF to pass).
(2) Blocks RF 1090 MHz to go to DC Adapter, but allows DC to pass un obstructed (an Inductor in series blocks RF, but allows DC to pass).


In TV/Satellite Splitter, the RF blocking Inductor is missing. Splitter's ALL ports are "RF PASS" :(:mad:
 
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ab cd

Senior Member
Hi everybody,
This is a very quality forum, i have a few antennas, one from FR24 (used by PF, FA and FR24), one for AIS and other for airband (dipole), how many cm or meters should be separated from each other?
Horizontal distance at least one wavelength: 275 mm for ADS-B(1090 MHz), 3000mm for Air Band (118-135 MHz).

If you dont have sufficient space horizontally, install these at different heights. In this case you dont need any large horizontal clearance.
 
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