ADS-B DIY Antenna

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ab cd

Senior Member
So you're what, a monarchist? :D
Actuay USA is not imperialist, Canada is.
USA kicked out the King in Civil war, while Canada still has a Queen. :D

Apart from joke, we should not have prejudice against any system. Every one feels comfortable in the system he has grown. This is similar to native language or mother tounge. Everyone feels comfortable using his native language.

I personally feel comfortable in all systems, as I have used all of these:
FPS (foot, pound, seconds)
CGS (centimeter, gram, seconds) - now abandoned in favour of MKS.
MKS (meter, kilogram, seconds)
SI (international standard units = rationalized MKS)
 
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DougJohnson

New Member
I was practicing to be a HAM many years ago. I learned Morse code, but then thought it sounded kind of boring exchanging dit and dots with someone.
Me, too. Even got my novice license. Just one more obsolete skill along with my slide rule abilities and my ability to hot wire a car.
-- Doug
 

DougJohnson

New Member
I personally feel comfortable in all systems, as I have used all of these:
FPS (foot, pound, seconds)
CGS (centimeter, gram, seconds) - now abandoned in favour of MKS.
MKS (meter, kilogram, seconds)
SI (international standard units = rationalized MKS)
I've used them all, too. Persistence of FPS is just plain crazy. I've got two complete sets of wrenches and then have to guess which set to use on the bolt in front of me. That sure makes sense.

One of the few things the French got right during their revolution was the metric system. Here is a great book about the adventure of determining how long the meter should be. http://www.amazon.com/Measure-All-Things-Seven-Year-Transformed-ebook/dp/B00AK9NWBU

And yes, it was a adventure. -- Doug
 

jepolch

Active Member
Me, too. Even got my novice license. Just one more obsolete skill along with my slide rule abilities and my ability to hot wire a car.
-- Doug
I actually got a 3rd Class radio operator permit to become a DJ, but never did. Now they don't need a permit.
 

trigger

Member
Do you have a feel for how much difference you were able to get? It is too late for me to try the terminal block idea for this one, but I am sure there are other things I could try. -- Doug
It's difficult to quantify but I'd say 50nm extra just by optimising the tap position.

@jepolch Thanks for the tips. So you got yours working good? How many elements? Will Diet Coke work OK? :D
Yes, I built several 6 element Franklins and found that I was able to repeat the build so gave up trying any more. I did fold the stubs around a piece of 20mm pipe to try to get it in a radome but never finished that project. The folding had no effect on the efficiency. Diet Coke will work just as well.

Yes, you can wiggle the connectors round the bends but it is better to put them on first.

The Franklin was my "best ever" antenna until I built an 8 element CoCo which added an extra few nm on my max range. I tried several CoCos before I got one to work :mad: I extended the CoCo to 24 segments and that is what I have attached to my RPi at the moment. It is inside some plastic pipe and outside above roof level. Outer ring is 250nm. As you can see my "splat" doesn't see that far to the South East due to the Chiltern Hills about 6 miles away. I'm building a Yagi to point in that direction which hopefully will give me some improvement.


upload_2015-3-14_19-32-46.png
 

xforce30164

Active Member
Some nice technical posts since I last visited the forum :). Will take some time to read them when I'm more awake, right now I got my 2nd pi running and currently got two receivers working, (actually can view them remotely as well, even data port)

dualreceivers.gif


got virtual radar running that combines the feeds from my during the weekends closest receiver near Amsterdam Schiphol Airpot, and remotely feed the data from Eindhoven aswell. Also, I am thinking about some way to make some hosted version of the interface that can combine both of these into an website/server hosted interface that grabs data from the receivers in a nice way. Also have been thinking of rewriting some of the UI to make a better "config` edit screen so it is more straightforward to edit variables/settings etc. Also got some ideas of making the coloring more customizable, but that will take some time to rework the code into a nice working concept. (I have my own website, from an older project unused, and really would love to make some kind of multi-screen customizable website/control room idea ^^)

Edit: here is a quick try hosted on my own website. (please don't abuse it ok? ^^)
 
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DougJohnson

New Member
It's difficult to quantify but I'd say 50nm extra just by optimising the tap position.
The Franklin was my "best ever" antenna until I built an 8 element CoCo which added an extra few nm on my max range. I tried several CoCos before I got one to work
My 8 element CoCo is my second best after the spider. The spider is back up now. I discovered a broken wire on the 6 element Franklin. So we can throw out all the previous complaints. Now we'll see if I get the energy to build another. Probably. Especially if Jepolch has some good results. -- Doug
 

xforce30164

Active Member
I just found this blog post of someone who posted about decoding ADS-B directly with an TP link router and openwrt. seems quite nice if it really works :D. (havent checked the price of the tplink router used)
 

jepolch

Active Member
I just found this blog post of someone who posted about decoding ADS-B directly with an TP link router and openwrt. seems quite nice if it really works :D. (havent checked the price of the tplink router used)
I saw that too. It crossed my mind during the short period I was running openwrt on my tp-link router, but I didn't really care for openwrt and soon switched to dd-wrt. Anyway, why do it on the router when when I'm already doing on the Pi (unless you don't have a Pi). By the way, Happy Pi Day! :)
 

jepolch

Active Member
OK, this is a repost of an epic post I just did over on FlightAware. I didn't want to send you over there to read it, so it's copied here verbatim. This was prompted by the original poster of the thread who is using a satellite diplexer as a bandpass filter (antenna to in/out port, sat port to receiver). It works with the power injector and amp although this test was done without power or amp. I haven't tried this setup with the Pi and dump1090 yet. This was done on the PC.

Warning! Lots of pics.

I did a series of tests today using three different antennas with and without the Holland diplexer. I have the (blue) DPD2 model and I believe Bob has the STVC (red). Here are the specs:


The testing took the whole day. Do you think it produced anything of value?

All the following tests were 20 sweeps:

Dipole no balun no diplexer


Dipole no balun with diplexer


Dipole with balun no diplexer


Dipole with balun with diplexer


8-legged spider (ground plane) no diplexer


8-legged spider (ground plane) with diplexer


Now, just for reference, the next two tests were with the dipole with balun, with diplexer, but connected to sat or vhf/uhf. I changed the range to 700-1200 MHz to see the cutoff of the bandpass filters.

Dipole with balun with diplexer vhf/uhf


Dipole with balun with diplexer sat


Since I've already eaten up a lot of bandwidth, I'll finish with a picture of the dipole with balun (also knows an a Pawsey stub) and the reference drawing.


 
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xforce30164

Active Member
I've had my Pi 2 for two days and haven't even plugged it in yet. Too busy playing with antennas. :D
I think I've already managed to mess up hdmi output,but was able to get it to work with the rasbian image and ssh. (NOOBS setup without screen was practically impossible :p. Also, my pi 2 was running quite hot now back at around 50°C after I added a small heatsink. (before temp was around 70°C)
 

jepolch

Active Member
I think I've already managed to mess up hdmi output,but was able to get it to work with the rasbian image and ssh. (NOOBS setup without screen was practically impossible :p. Also, my pi 2 was running quite hot now back at around 50°C after I added a small heatsink. (before temp was around 70°C)
How do you think you messed up the HDMI, break a connector on the board? I haven't gotten the heat sink kit for the Pi 2 yet. I've been thinking of making one out of scrap aluminum.
 

DougJohnson

New Member
I did a series of tests today using three different antennas with and without the Holland diplexer.

The testing took the whole day. Do you think it produced anything of value?
1) Unless you have an overloading problem, the diplexer hurts not helps.
2) The balun is a big help.

-- Doug
 

ab cd

Senior Member
.......snip......
The balun is a big help.

-- Doug
How about 1:1 "Sleeve Balun" or "Bazooka Balun"?

Source: ECE Dept, McMaster University, Ontario, Canada. Antenna Lectures by Prof. Natalia K. Nikolova
Balanced-to-unbalanced feed
Sometimes, when high-frequency devices are connected, their impedances might be well matched, and still we may observe significant reflections. This is sometimes referred to as “field mismatch.”
A typical example in antennas is the interconnection between a coaxial line of Zc = 75Ω and a half-wavelength dipole of Zin= 73Ω. The reflections are much more severe than one would predict using equation Γ2 = {(SWR-1)/(SWR+1)}2. This is because the field and the current distributions in the coaxial line and at the input of the wire dipole are very different [see figure below]. The unequal currents on the dipole’s arms unbalance the antenna and the coaxial feed and induce currents on the outside of the coax shield which are the reason for parasitic radiation. To balance the currents, various devices are used, called baluns (balanced-to-unbalanced transformer).

unbalanced currents in coax.png



Sleeve (bazooka) balun 1:1
The sleeve and the outer conductor of the coaxial feed form another coaxial line, which has a characteristic impedance of Z′c. This line is shorted quarter-wavelength away from the antenna input terminals. Thus, its input impedance is very large and results in: (i) suppression of the currents on the outer shield (I3), and (ii) no interference with the antenna input impedance, which is in parallel with respect to the coaxial feed. This is a narrowband balun, which does not transform the impedance (1:1 balun).
bazooka balun 1.png
 

trigger

Member
@jepolch The testing took the whole day. Do you think it produced anything of value?

Great work. What you need to do next is run each setup for a week (or 2) and see how your stats look. ;)
 
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