Topic: FlightRadar24 uses TDOA for locating aircraft

[dfroula]

I have an experimental web page set up that shows a real-time image of my PlanePlotter ATC display. I currently have it set to update every 30 seconds. The image size and detail reflects whatever zoom level and details I have enabled at the moment.

The display shows range rings centered on my location. Each ring represents 25 nautical miles.

Plane locations with yellow text are those being received directly by my antenna and receiver system. Planes with blue text are from shared data with other stations in the network.

Planes marked by a white diamond are those located by TDOA techniques (currently a manually-initiated process).

Airports are in red. Larger airports show the airspace range rings surrounding them. Small white triangles are station locations or navaids (NDBs or VORs), depending on how I have the display set at the moment.

http://projectmf.homelinux.com/planeplotter.html

Refresh your browser if the image is missing or incomplete because it was updating during the browser automatic refresh.

Regards,

Don
WD9DMP

[W3DRM]

Don - that's neat! 

Have been watching some traffic going over your location and comparing the tracks between PP and FR. I notice that there are currently several aircraft almost overhead your location at 25K to 33K and one going in the opposite direction at around 10K. Only the 10K aircraft shows up on PP while it does show on FR. I suspect that is due to your antenna pattern favors the horizon rather than vertical reception.

Anyway, great job. It looks really nice. I am jealous...

[CamarilloWX]

That is really cool.

[dfroula]

Don, since the RTL1090 decoder program and PlanePlotter support relative signal strength indications, I turned them on and observed a few overhead flights. In all cases the signal strengths peaked as the planes flew overhead and diminished rather quickly as they moved on. However, I was able to continue tracking most planes directly out to 150 to 175 nm.

The signal strength indication (0% to 100%) now shows as the last two digits of each plane's descriptor on the display, so you can check yourself. The RSSI is a bit weird. I tried turning off the two AGCs on the dongle. The relative signal strengths increase dramatically across the board, but there is no change in coverage as long as I set the gain to maximum (which the AGC is likely doing anyway). I don't think the increase is "real" but just a scale shift as to what is reported by the decoder.

I have auto-MLAT TDOA positioning enabled. When the program is idle and detects a positionless aircraft (transponder S-Mode without ADS-B data) with enough other stations reporting, the program tries to run the MLAT routine by setting up direct UDP connections to nearby stations and exchanging timing information. Very few of these attempts result in a position fix. Perhaps it has to do with the geometry of nearby stations. There are about 15 in my area (within 150 nm).

Regards,

Don
WD9DMP

Don - that's neat! 

Have been watching some traffic going over your location and comparing the tracks between PP and FR. I notice that there are currently several aircraft almost overhead your location at 25K to 33K and one going in the opposite direction at around 10K. Only the 10K aircraft shows up on PP while it does show on FR. I suspect that is due to your antenna pattern favors the horizon rather than vertical reception.

Anyway, great job. It looks really nice. I am jealous...

[W3DRM]

Don, thanks for the explanation. I do like the signal-strength showing on the track too.You do have great coverage. How high up do you have your antenna?

I found a new location to put my antenna when it comes. It will be much easier getting to and won't require my climbing a 24-foot ladder to get to it. The only problem is that it is more than 10 meters away from where I have to place my FlightRadar25 box (in my garage). I may have to place the box closer to the antenna and then use a longer cat-5 cable from the box to the router. According to DHL, my shipment is still sitting in Germany being put together for international shipping.

Don, since the RTL1090 decoder program and PlanePlotter support relative signal strength indications, I turned them on and observed a few overhead flights. In all cases the signal strengths peaked as the planes flew overhead and diminished rather quickly as they moved on. However, I was able to continue tracking most planes directly out to 150 to 175 nm.

The signal strength indication (0% to 100%) now shows as the last two digits of each plane's descriptor on the display, so you can check yourself. The RSSI is a bit weird. I tried turning off the two AGCs on the dongle. The relative signal strengths increase dramatically across the board, but there is no change in coverage as long as I set the gain to maximum (which the AGC is likely doing anyway). I don't think the increase is "real" but just a scale shift as to what is reported by the decoder.

I have auto-MLAT TDOA positioning enabled. When the program is idle and detects a positionless aircraft (transponder S-Mode without ADS-B data) with enough other stations reporting, the program tries to run the MLAT routine by setting up direct UDP connections to nearby stations and exchanging timing information. Very few of these attempts result in a position fix. Perhaps it has to do with the geometry of nearby stations. There are about 15 in my area (within 150 nm).

Regards,

Don
WD9DMP

Don - that's neat! 

Have been watching some traffic going over your location and comparing the tracks between PP and FR. I notice that there are currently several aircraft almost overhead your location at 25K to 33K and one going in the opposite direction at around 10K. Only the 10K aircraft shows up on PP while it does show on FR. I suspect that is due to your antenna pattern favors the horizon rather than vertical reception.

Anyway, great job. It looks really nice. I am jealous...

[dfroula]

Don, the antenna is up on the roof about 45 feet. I have the 1-meter PVC antenna enclosure clamped to a short piece of thicker diameter PVC as a mast to clear the roof peak.

That FlightRadar box is nice in that it is self-contained. A 125 foot run of CAT5 is more forgiving than the same length of coax! I don't have that option, as the receiver dongle is USB only. There is some Raspberry Pi decoder code available, so I could turn the dongle into a poor man's version of the FlightRadar24 box.

Now that I know what the system can do, I'm eager to see if I get approved for the hardware. Still no word back.

Best,

Don
WD9DMP

Don, thanks for the explanation. I do like the signal-strength showing on the track too.You do have great coverage. How high up do you have your antenna?

I found a new location to put my antenna when it comes. It will be much easier getting to and won't require my climbing a 24-foot ladder to get to it. The only problem is that it is more than 10 meters away from where I have to place my FlightRadar25 box (in my garage). I may have to place the box closer to the antenna and then use a longer cat-5 cable from the box to the router. According to DHL, my shipment is still sitting in Germany being put together for international shipping.

Don, since the RTL1090 decoder program and PlanePlotter support relative signal strength indications, I turned them on and observed a few overhead flights. In all cases the signal strengths peaked as the planes flew overhead and diminished rather quickly as they moved on. However, I was able to continue tracking most planes directly out to 150 to 175 nm.

The signal strength indication (0% to 100%) now shows as the last two digits of each plane's descriptor on the display, so you can check yourself. The RSSI is a bit weird. I tried turning off the two AGCs on the dongle. The relative signal strengths increase dramatically across the board, but there is no change in coverage as long as I set the gain to maximum (which the AGC is likely doing anyway). I don't think the increase is "real" but just a scale shift as to what is reported by the decoder.

I have auto-MLAT TDOA positioning enabled. When the program is idle and detects a positionless aircraft (transponder S-Mode without ADS-B data) with enough other stations reporting, the program tries to run the MLAT routine by setting up direct UDP connections to nearby stations and exchanging timing information. Very few of these attempts result in a position fix. Perhaps it has to do with the geometry of nearby stations. There are about 15 in my area (within 150 nm).

Regards,

Don
WD9DMP

Don - that's neat! 

Have been watching some traffic going over your location and comparing the tracks between PP and FR. I notice that there are currently several aircraft almost overhead your location at 25K to 33K and one going in the opposite direction at around 10K. Only the 10K aircraft shows up on PP while it does show on FR. I suspect that is due to your antenna pattern favors the horizon rather than vertical reception.

Anyway, great job. It looks really nice. I am jealous...

[dfroula]

Cleaning up the connection to the dongle from the first picture to the second made a BIG difference in signal strength and consistency of range. I removed the adapter stack and long length of mini-50 ohm coax and replaced it with this short adapter I built.

The satellite cable and antenna are both 75 ohm. The adapters and pigtail coax are 50 ohm. It appears the mismatch and impedance bumps had a significant impact on the signal.

Regards,

Don
WD9DMP

[KennyBKK]

Hi,

I have an ADS-B called RadarBox for over a year now.  Also feed data to Flightradar24 as T-VTBD1 (Bangkok, Thailand) for some time.   The RadarBox is not similar to FR24 box that they currently provide but I will happy to share my experience on 'PlaneSpotting'.

Kenny

[W3DRM]

Hi,

I have an ADS-B called RadarBox for over a year now.  Also feed data to Flightradar24 as T-VTBD1 (Bangkok, Thailand) for some time.   The RadarBox is not similar to FR24 box that they currently provide but I will happy to share my experience on 'PlaneSpotting'.

Kenny

Hi Kenny, welcome to the forum! Any inputs regarding ADS-B would be greatly appreciated. Most of us here are relatively new to the subject. I am currently waiting for my FlightRadar24 equipment to arrive. Hope to have it sometime next week. In the meantime, I'm reading everything I can find and also building a mount for the antenna. That should be completed sometime tomorrow.

[Silversword]

Hi,

I put in my application for this system as well.  Got to step two and sent them the necessary info.  Now the wait.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii

[W3DRM]

Hi,

I put in my application for this system as well.  Got to step two and sent them the necessary info.  Now the wait.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii

Of course, you told them your QTH was atop Haleakala, right? 

Good luck with your application!

[Silversword]

Of course, you told them your QTH was atop Haleakala, right? 

Good luck with your application!

Yea, would have been nice to do that but I am on the slopes of Haleakala at 1,500 feet and about 10 miles below me is Kahului Airport (OGG).  I forgot to mention the airport but did mention the height above sea level and probably have a coverage of about 120 miles.  Hope that would help with the assement.

Will just wait and see what happens.

How long did you have to wait for a response from them?

CUL,

--Stan Y.
   KH6HHG
   Maui, Hawaii

[W3DRM]

Of course, you told them your QTH was atop Haleakala, right? 

Good luck with your application!

Yea, would have been nice to do that but I am on the slopes of Haleakala at 1,500 feet and about 10 miles below me is Kahului Airport (OGG).  I forgot to mention the airport but did mention the height above sea level and probably have a coverage of about 120 miles.  Hope that would help with the assement.

Will just wait and see what happens.

How long did you have to wait for a response from them?

CUL,

--Stan Y.
   KH6HHG
   Maui, Hawaii

It took about 4 to 5 days to get a response after I sent in my detailed application with the photos. However, looking at their needs list, Hawaii shows they need equipment in the entire State so you may have a good shot. With your altitude at ~1500 ft you should have a clear view of air traffic all the way to Honolulu as well as traffic coming in from Asia and the US mainland. Of course, you're shadowed from the Big Island but I doubt that would matter since you appear to have great coverage everywhere but to the southeast.

Since they ask if you are a radio operator (ham?), I suspect they are favoring those of us who are hams since we do have a better understanding of what is needed for good reception and that we are less likely to need hand-holding getting the equipment set up.

Looking at the traffic in Hawaii, I see none showing ADS-B modes.

[KennyBKK]

Hi,

I have an ADS-B called RadarBox for over a year now.  Also feed data to Flightradar24 as T-VTBD1 (Bangkok, Thailand) for some time.   The RadarBox is not similar to FR24 box that they currently provide but I will happy to share my experience on 'PlaneSpotting'.

Kenny

Hi Kenny, welcome to the forum! Any inputs regarding ADS-B would be greatly appreciated. Most of us here are relatively new to the subject. I am currently waiting for my FlightRadar24 equipment to arrive. Hope to have it sometime next week. In the meantime, I'm reading everything I can find and also building a mount for the antenna. That should be completed sometime tomorrow.

Hi W3DRM de HS1PDY..

As I heard from a friend who has FR24 box, the setup is quite easy.  Just plug it to a LAN port and mount the antenna as high as possible with clear direct view.  Given the ADS-B use 1090 MHz which is microwave range the higher the antenna, longer range it can receive.  I put mine on top of the roof about 8m from the ground using 12m RG-8 coax and get a range around 200-240nm without amplifier.  The FR24 box has built-in amplifier which should give a better result.

regards,
Kanok

[W3DRM]

Hi Kanok,

Thanks for the info. Still no word about my shipment from Germany so not sure when the FR24 equipment will arrive.

73's

[Jumpin Joe]

I emailed FlightRadar24 to check on my approval status.  Looks like I am on the waiting list.

Here is the response....

"I can confirm that we have received all the required information and you are on the waiting list.

The list is reviewed once a week but it can take many months for a location to be approved.

We will contact you again when your location is chosen.

Thank you for offering to support Flightradar24.com."


So I wait......

[Silversword]

I emailed FlightRadar24 to check on my approval status.  Looks like I am on the waiting list.

Hi Joe,

Where did you find the email address to check on your status?  It has been just over a week since I put in my second stage info.  Maybe another week of patience before I email them for a check of status.

Regards,

--Stan Y.
   KH6HHG
   Maui, Hawaii
 

[SoCalBrian]

You can email Mike for your feeder offer status.
mike@fr24.com or support@fr24.com

[Jumpin Joe]

You can email Mike for your feeder offer status.
mike@fr24.com or support@fr24.com

Yep, that's it!

[Silversword]

Thanks for the info. Will try later as I am away from home now.

--Stan Y.
    Maui, Hawaii

[dfroula]

I cleaned up my antenna installation some this past weekend. I replaced the F-connector grounding block with a nice Polyphaser coaxial surge/lightning suppressor. It uses "N" connectors and is designed for cellular tower use just above 1090 MHz. Just replacing that crappy 20-year old grounding block bought me another 50 nm of range and much higher packet rate.

The suppressor is nice. It provides DC continuity, but clamps the voltage on the center-conductor to -1.0 to +6.0 VDC. I am pretty sure it has gas discharge protection tubes inside. It is supposed to be great at draining static build-up from wind and approaching electrical storms

I also ordered this LNA from Adam,  a ham in Croatia:

http://lna4all.blogspot.com/

It offers 19 dB of gain at 1090 MHz. It is very broad-band and usable from 28MHz to 2500MHz. The delivered cost is 25 Euro, with SMA connectors. He doesn't ask for ANY payment until the LNA is received. His unit uses a Minicircuits IC. It is comparable to a Minicircuits built  LNA unit costing $150.00+.

With that kind of bandwidth and gain, I figured I needed some kind of pre-selection before the amp to avoid saturating the R820T dongle. I also ordered this bandpass filter from Minicircuits:

http://www.minicircuits.com/pdfs/VBFZ-1065+.pdf

The pass band is 980 MHz to 1150 MHz with 1.68 dB insertion loss at 1065MHz. This is far superior than SAW devices, which must almost always be placed after the LNA because of their very high insertion loss. Cost of the filter (SMA connections) is $39.00 plus $9,00 shipping within the US.

My final antenna system lineup will be:

8-element coax collinear antenna > Polyphaser impulse protector > pass band filter > LNA > R820T receiver.

Regards,

Don
WD9DMP

[W3DRM]

Don, which Polyphaser model did you get? Was it the "IS-50NX-C2-MA"?

Polyphaser used to be located right here in Minden, NV. I knew the owner/founder (Roger Block - KD7UT). He is now a SK after suffering a major heart attack a year or so ago. Really a nice guy. I believe the company is going to be moving to someplace in Utah this summer.

[dfroula]

The Polyphaser model is a new IS-MR50LNZ+6. It is designed for protection of a tower-mounted GPS antenna used for a cellular base station timing reference, hence its tolerance for the +5 phantom voltage on the cable to power the LNA in the GPS antenna itself. It is spec'ed at <=0.1 dB insertion loss at those frequencies.

I'm not using a bias-T power injector configuration to power the LNA over the cable (although it will support the configuration with an additional inductor and capacitor), so there is no normal DC voltage at all on the cable.

It seems to work just fine for ADS-B. It's far better than a spark gap! It has been sitting in the RF junk box, unopened, for 10 years or so. I'm pleased to have put it to good use.

I do see on the spec sheet they are (were) located in Minden!

Best,

Don
WD9DMP

[SoCalBrian]

It has been just over a week since I put in my second stage info.  Maybe another week of patience before I email them for a check of status.

If you never hear back from FR24. (I also had emails to them and they never responded back)

You could look at requesting the free FlightAware FlightFeeder box.
With the FlightAware box and software. You can share with any other network sites(Planefinder,PlanePlotter,RadarBox24,FR24,etc) running 1 box from your location. (saving electricity

* Can I share data from FlightFeeder with other sites?
Sure! FlightAware encourages the sharing of all available ADS-B data for maximum collaboration and sharing within the community.
http://flightaware.com/adsb/faq#sharing

You could also watch other WX user boxes on the FlightAware Stats page.
http://flightaware.com/adsb/stats/sites

Flightradar24 doesn't allow sharing to other network with their box.

Some installed photos of the FlightAware box and FR24 box on this page from some Canada user on this page.
http://ads-b.ca/

From my California location I upload to FR24,PlaneFinder,FlightAware, Planeplotter and Live-Mode-S site.


You will also see more details on sites like Planefinder.
You should view both sites Side-by-Side for comparison.
More business/private aircraft details(tail numbers) will be displayed on PlaneFinder.net
Plus the local Coast Guard in San Diego area will show up on Planefinder.  FR24 doesn't show it.
Like Google company jet N2767 details will show up on Planefinder and not FR24.

[W3DRM]

It has been just over a week since I put in my second stage info.  Maybe another week of patience before I email them for a check of status.

If you never hear back from FR24. (I also had emails to them and they never responded back)

You could look at requesting the free FlightAware FlightFeeder box.
With the FlightAware box and software. You can share with any other network sites(Planefinder,PlanePlotter,RadarBox24,FR24,etc) running 1 box from your location. (saving electricity

* Can I share data from FlightFeeder with other sites?
Sure! FlightAware encourages the sharing of all available ADS-B data for maximum collaboration and sharing within the community.
http://flightaware.com/adsb/faq#sharing

You could also watch other WX user boxes on the FlightAware Stats page.
http://flightaware.com/adsb/stats/sites

Flightradar24 doesn't allow sharing to other network with their box.

Some installed photos of the FlightAware box and FR24 box on this page from some Canada user on this page.
http://ads-b.ca/

From my California location I upload to FR24,PlaneFinder,FlightAware, Planeplotter and Live-Mode-S site.


You will also see more details on sites like Planefinder.
You should view both sites Side-by-Side for comparison.
More business/private aircraft details(tail numbers) will be displayed on PlaneFinder.net
Plus the local Coast Guard in San Diego area will show up on Planefinder.  FR24 doesn't show it.
Like Google company jet N2767 details will show up on Planefinder and not FR24.

Thanks for sharing those links. They are quite helpful and also bring up a few questions too.

• If all of the various sites are gathering ADS-B data from the aircraft, why don't they all show the same information? I can see where each of them probably has their own aircraft databases but all are receiving the same flight details. Is it just that they have each chosen which of the received data they are going to display?

I jumped at the opportunity to get the FREE FR24 receiving equipment. Now, I'm wondering if I should have waited and dug into the details more than I did. I was not aware of all of the other ADS-B offerings available.

Oh well, guess I'll just wait and see how I like once it gets here. My system is still in transit from Germany via DHL but their package tracking doesn't provide any kind of estimated delivery date.