Confused with ADS-B range

FlightAware ADS-B Flight Tracking
1

Hi,
Long time Reader first time poster here. :grin:

A number of years ago I made a Cantenna, mounted at about 35 m inside my loft. Approximate 5m WF100 down lead to generic cheap TV tuner, connected to a Raspberry Pi.
This gave me around 800 aircraft a day, A maximum range of 155 nautical miles, and an average range of around 100nm. Gain set too max (Based in the Vale of York, the topography of the land Is against me in most directions)

After around three years, Iā€™ve decided to revisit this and replaced the homebrew antenna with a commercial one from the pie hut.

It was mounted in the same position, and my range didnā€™t really increase but the number of aircraft increase to around 1000 a day.

Disappointed with this, I moved the pi Into the loft shortening the lead to the antenna to around 1.1m, The range immediately increased to max of 175nm, and I was frequently seeing A daily maximum range of 165 nautical miles.
(Occasionally, ones are over 300, but they were rare)

After this performed consistently for a week, I decided to connect the receiver directly to the base of the antenna. Thinking this would remove more attenuation in the Cable, however my range dropped to 5nm, The number of detected aircraft was less than 20 a day!
So I very quickly replaced the original cable, and the range returned back to the previous values.

I then tried shortening the lead to around 85cm to tidy up any trailing cables in the loft rather than any specific theory about the range. I then noticed that my daily maximum range had dropped to 150nm, I was no longer seeing anything around the 165 miles to the 175 range. (Thinking I should stuck to the Can!)

I have now tried a cable at approximately 1.35 m, which is around 10 half wavelengths. Detections have increased by about 10 -15% (1200 daily) with no increase in range, itā€™s now sat at 138nmā€¦

What can I do to boost the range?

Was I just lucky with 1.1m? Or did I hit some magic multiple of wave lengths?

Im assuming my issue is related to interference? There is very little local traffic with airports all been 30mikes away.

Would I be better purchasing a filter for around Ā£25. I read good reviews about these.

Or buying the FA ProStick Plus as this has a filter and a LNAā€¦ would this then be happy connected to the base of the antenna?

Thanks :pray:

1 Like
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Just jumping in here to look at some possibilities. As long as your attic is not under a metal roof, you will get reception of ADSB signals, with some loss due to the materials of the roof. Rain will decrease the signals too. My primary antenna is in my attic at about 8 meters / 25 ft above the ground level. LOTS of trees all around me too.

Shortening the antenna cable reduced the signal loss, always a good thing. Your experiment with the receiver dongle at the base of the antenna could be a problem with the connectors or interference from the receiver, the PI or the power supply making noise at the ADSB antenna, just thinking and writing here. One thing that will help is installing Graph1090 on your system. Great diagnostic tool. Graphs for dump1090 -- my version with install script

One thing to be aware of, not all SMA connectors are alike. There are some with the center pin and others that have no pin. That could easily account for the direct connection losses. The no pin on the male connectors are know as RP-SMA, Reverse Polarity. Probably not the problem, but it has messed up people as we play with our systems to improve as you are doing.

Maybe this can give you some ideas to chase down. The FA ProStick Plus with the filter and LNA is a good product and might give you a good way to extend your range.

Have fun with improving your system. Best wishes always.

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thanks for the reply. FA ProStick Plus is looking goodā€¦ The current recover is a good 10 years old

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10 years is significant. Older TV hardware and power supplyā€™s had higher noise figures, and probably radiated some noise picked up by your antenna. With the automatic gain controls on older hardware, the ADSB signals could easily be swamped by the nearby receiver. FA Blue receiver and some of the others have good characteristics, and yes, I have three of the blue receivers used for experimentation. The FA receiver comes with a standard SMA female connector. Most any Raspberry Pi will work with the FA receiver dongle also, so your current Pi should be fine. Kinda fun to have 10 year old stuff still working and contributing. If you still have the Cantenna top, you could repurpose it to become a ground plane for that newer antenna. Not sure if it would make a difference, but a good experiment to explore.

Again, have fun with this.
Gene

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5

Try backing off the gain and see how that changes the performance.

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Thanks to everyone that has replied. Yes, the hardware is around 10 years old, it was originally purchased around the time of the digital switch over for TV.

It didnā€™t really work as it was dangling out with your laptop and wasnā€™t really usable.

So he sat on used until 2017, when it was discovered in a box and repurposed.

After the comments here, and a bit more reading, I have gone for the FA pro stick plus.

Regarding using the old cantenna as a ground plate for a new one. Would that simply be screwing it into place at the base of the new antenna? Presumably on the SMA connector.

Thanks again

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I dont understand - is the ADS-B system you presently use in your aircraft, ā€œhome-madeā€ like the one you use on the ground? If so, may I recommend going to one approved for use in aircraft. In my own case (Garmin products) the range is more than adequate for air traffic safety. What am I missing here ?

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Itā€™s on the ground, no aircraft in this case

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geckoVN made a good observation above about changing the gain to see what is optimal for your setup. It will definitely make a difference on your new FA pro stick plus. Let us know if your new FA pro stick plus makes a difference for your system.

Your antenna has an N female connector. I will be doing some experimentation on a similar antenna here, adding a circular ground plane at the base of the antenna against the metal mounting cylinder. I will use a compatible nut and washer to hold the ground plane in place. Not sure if it will make a difference, just experimenting. I will do some testing with a nanoVNA (small Vector Network Analyzer) to see if it changes the impedence of the antenna and swr measurement. If it makes a difference, I will post something here in the forums.

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Something odd hereā€¦why would someone who is not an aviator, give a damn about ADS-B and where those who do fly, happen to be in any given moment. Be assured I could care less if folks know where my airplane and I areā€¦but why would a non-aviator care more than lessā€¦? (maybe my legs arenā€™t as cute as Taylor Swiftsā€¦?)

11

Range heavily depends on the geographical situation and the environment. If tall buildings or trees are in range, it impacts your device.
Also far distance mountains blocks it.
Finally some electronic interferences in your area also do have an impact.

This cannot be fixed with changing antennas only.

What you can also try it different values for gain. Setting it to ā€œmaxā€ is not always a good idea.
install the graphs from wiedehopf and monitor it for some days.

The number of messages larger -3dbFS should not exceed 5%. If you are getting close to that value, you have it optimized.

1 Like
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I canā€™t speak for others, but even though I am not a pilot, I find it interesting to be able to see what is in the sky around me. I fly several times per week as a passenger on commercial airlines - over 1100 flights in just over 8 years. That has given me an interest in seeing which planes are going where.

I have even paid for WiFi on a flight one time so that I could remote into my ADSB receiver at home and ā€œwatchā€ the plane that I am on fly over my house.

So, why do people have in interest in it? Who knows. Some people collect Beanie Babies.

6 Likes
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Quick updateā€¦ the new stick arrived to dayā€¦ connected and and workingā€¦
Range was not impressive, no real improvementā€¦

I literally had 171nm form a tin can and a cheap DVB tunerā€¦

Now commercial Antenna, and FA stick, getting nothing close.

I have checked and it seem the Pi4 was having power issues, thatā€™s now fixed.
AGC has been set and going to now give it a few daysā€¦

would grounding the base of Antenna to earth help? (not my area sorry)

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Grounding is more of a commercial / Ham Radio / lower frequency external antenna kind of thing. One grounds an antenna tower or vertical antenna to get a virtual ground to act as part of the antenna and make the antenna work better. At the ADSB wavelength, the ground is generally a long way away from the antenna location and has little effect. Your tin can top was a better ground for an 1090 MHz antenna than some #8 wire through a wall and connected to an 8 ft copper post into your local soil. Lightning is one reason we ground towers, as lightning has a nasty way of messing up electronics. I know this from personal experience. Definitely not a good conversation with your significant other.
I hope your system recovers soon. Generally reception problems are in Antennas, connectors, cables, filters, receivers, and the software settings used to drive the systems. Power issues can definitely affect you too. Perhaps you can find a different Pi and try to run on different hardware a bit. It can help rule out the Pi portion of the system. Best wishes to you. Do you know any other local ADSB people nearby? Perhaps one of them might be able to help.

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So this morning I managed to grab a quick screenshot, now there are some flights
Many flights that I would expect to see routes, distance, speed etc are missing this information.
Previously I never saw anything like thisā€¦
(This is Antenna, Receiver, Pi, with AGC set)

Screenshot 2024-03-13 070150
Screenshot 2024-03-13 070150716Ɨ678 212 KB

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Route info can be hit-and-miss with VRS as they are all picked up from call signs and have to be manually added.

Iā€™m in the Tees Valley with good open space I use a PI 4, PI Hut 60cm antenna (loft mounted) and the blue dongle and get this range

image
image1587Ɨ890 176 KB

Itā€™s possible your location in the Vale of York is struggling with signals getting blocked also with VRS do you have MLAT data merged in along with adsb?

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Thanks, thereā€™s helpful.
My issue is I used to get this range on a tincan and a cheap receiver.

Now with better equipment I get a fraction of the coverage.

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My take is that max range is not really interesting. Living close to an airport and close to several large cities there is enough receivers to cover all flights that might be relevant far away. It is more important to have good coverage locally - like you say Dave your location is difficult, then consider the guy living on the other side of the mountain? After all the point of having multiple receivers is to share data so services like FA for example can put the data together on a nice map. A matter of taste really but try to get good coverage locally, it can mean setting gain quite low so that the aircraft overhead doesnā€™t max out the receiver (dotted lines on local map or suddenly not being tracked while passing over).
And for us pilots, use of local ā€œradarā€ can be very useful, see for example https://www.safesky.app/en.

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Here you can see what I was getting, and roughly what I was getting now.
Itā€™s not that the topology has changed, it always been like thisā€¦

Plot
Plot1529Ɨ1342 365 KB

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Did you get a new cable with the antenna from pi hut?