Directional antenna for ADS-B?


#1

Hi, does anyone have experience with directional antenna’s for ADS-B? Which model would be best? A yagi with low bandwidth seems difficult to homebrew without proper measuring equipment & buying ons seems expensive (Jetvision 13 element yagi).
This Bulgarian one is a heck of a lot cheaper, greater beamwidth and marginally less gain.
Then I find many writeup’s about corner reflectors (screen in the back, dipole in front) - 90 degree beamwidth however I have not found any sizes (definitive formula’s) to use for ADS-B, nor have I seen anyone that made one or uses one.
As this is a hobby I don’t mind putting some money in it to purchase something but price has to be within reason as antenna’s are only single purpose: for one frequency only.

Any hints, tips, suggestions?


#2

Try this online calculator:

https://www.changpuak.ch/electronics/yagi_uda_antenna_DL6WU.php


#3

@JoePPi
@Dxista

These may help:

1. Directional antennas

2. Directional antenna

3. yagi - do you have experience with directional antennas?


#4

A Pictorial Guide “How to Mount Directional Antenna Yagi” :rofl:

.
mounting%20tv%20yagis%20-3

.
.

mounting%20tv%20yagis%20-%202

.
.


#5

@Dxista
@abcd567

Thanks for the links, I am familiar with yagi design & it’s difficulties. Have been in attendance of DL6WU and his successor DK7ZB who has improved on his design.
And yes, I’m quite aware of the possibilities of yagi’s . Scale this to 1090MHz for maximum range. However, for ADS-B it would be impractical to duplicate.

I am mainly looking for real-world results. I have some crazy idea which would require a directional antenna, lightweight, some gain but a very high F/B ratio. I live in an area with many, many planes all around and I feel l miss many as a result of false decodes/collisions.
I want to set up an SDRPlay receiver with a high F/B directional antenna but it should not have to narrow of a beamwidth. That is why the corner reflector came to mind and the Bulgarian alternative seems attractive. But I can barely find any real-world experiences to determine if it’s worth making any effort.

My primary feed is a Bulgarian coco @ 9m with an FA Blue stick. The second is a standard whip + RTL stick (China) @ 3m (side of the house), the third is an SDRplay RSP2 (overkill for this purpose) with a 5/8 Kathrein for 144MHz @ 4m (other side of the house).
The interesting thing is that the RSP2 gets a very high message rate compared to the other feeds. I may move it to the location of feed 2 for comparison.
But I believe that a rotating directional antenna such as a corner reflector might bring many more planes. Continuously rotating an antenna seems possible and seems worth investigating (longer term project though). But first the “right” antenna.

So still looking for real world observations about the various antennae compared to a vertical even though I’m not sure some objective comparison can be made.


#6

@JoePPi

What about:

1. Corner Reflector

2. Cubical Quad

3. Bi Quad


#7

I have several directional mesh type antenna for 980Mhz-1.2Ghz. I use mine for 978Mhz at the moment.
I can’t find them online any more.

This one is cheaper than the jetvision yagi.
https://www.moonraker.eu/antennas/avionic-antennas-radar-sbs-airnav/radar-yagi-1090mhz-directional-antenna

The problem with DIY directional antennas at these frequencies, is that they have very tight tolerances. Lots of people have had issues just getting vertical antennas to work well.


#8

I use the Jetvision yagi here in Australia.
Its very good and very well constructed, not likely to break in a hurry.
So far have received signals as far as 1134 km using it.
You get what you pay for as they say.

Leigh


#9

That’s probably not because of antenna, but because of troposphere reflections.


#10

Yes… it was because of the antenna, as the omni vertical antenna I am also using on a 2nd receiver was only hearing approx half the distance at the same time.

It was during tropospheric duct opening (refraction not reflection). But you still have weak signals at the peak distances that the propagation is coming from. If you have an antenna that can bring in these weaker signals then you are going to hear further than one that cant do that, or doesnt have as much gain etc.

But the down side can be, when you have more gain, you have less beam width, and thus you can miss signals that are outside the main lobe of the antenna and you would have to swing it about more with a rotator if you want to cover more of the sky.

See the AIS & ADSB Long Distance page on facebook,


#11

Sorry, not using facebook. Ever…


#12

@all
Thanks for your remarks and suggestions. Yes, often you get what you pay for but not always.

My next step will be to try to put together a corner reflector based on the @abcd567 model, however it will only be one quarter, not four. Sadly corner reflectors (or dipoles with a mesh reflector) appear not commercially available so I will start sourcing some materials and try to find a method for tuning the needed dipole.

If and when completed (…) I’ll let y’all know the results. O, and that will like @SoNic67 also NOT be on facebook.


#13

5.4 GHz Sectorized Omnidirectional Antenna Array

.
.


#14

You know that there are phasing issues with four antennas connected like that? If the cables are not perfectly identical, the resulting diagram won’t look like that.


#15

@SoNic67
Yes, an accurately built phasing harness is required for such an arrangement. Commercial antennas like this are supplied with all accessories including trimmed and tested phasing harness cables.

In the photo, there is a splitter box and 4 coax cables from 4 units to splitter box. Sure all these are supplied by antenna manufacturer.


#16

This seems like a good arrangement if there isn’t too much signal interference for the various directions. Looking at “random” (in time) ADS-B signals this would lead to less good decodes due to interference which is why I am looking to limit the skyview to a smaller section with good F/B ratio and that way get more and farther decodes. The next step would be to combine the results per sector after decode or to switch directions every n seconds or so - like a radar setup for receive only.


#17

Providing each sector with a decoder would minimize the collision domain for the actual ADS-B data signals, so it will be beneficial.
However it is difficult to integrate the sectors in one feeder, due to timing issues, so you might end up with four separate feeder sites on FA or FR24 actual websites. Don’t know if that is an issue with OP or not.


#18

Example of Mag Mount Whip with Corner Reflector
.
https://www.rtl-sdr.com/tag/corner-reflector/

.


#19

Technical article about the Corner Reflector Beam Antenna by the inventor John D. Kraus.

Kraus, John D. (November 1940). “The square-corner reflector beam antenna for ultra high frequencies” (PDF).

QST. USA: American Radio Relay League. p. 18.