FlightRadar24 app ADS-B "IN" only displays aircraft if your at an altitude that their receiver can pick up.

All_In

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Of course not. Use as "ADS-B in" is not even remotely the purpose of the program. Flightradar24 is simply a tracking service.

If you are not in range of a Flightradar24 receiver you get nothing, and your aircraft will not be seen by Flightradar24 users.

From Flightradar24.com:
Flightradar24 has a network of more than 20,000 ADS-B receivers around the world that receive flight information from aircraft with ADS-B transponders and send this information to our servers. Due to the high frequency used (1090 MHz) the coverage from each receiver is limited to about 250-450 km (150-250 miles) in all directions depending on location. The farther away from the receiver an aircraft is flying, the higher it must fly to be covered by the receiver.
Thank you for the rest of the Flightradar24 story.
Wish you would have shared that with the forum and Dave before now. I believe most expected it to use the GPS satellites that could reach everywhere.

I've never used Flightradar24 so I did not know.

Dave was using it as his primary ADS-B "IN" and for tracking friends' flights.
He was in total disbelief to learn it is not sending and receiving from satellites and had holes.
 
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WaspAir

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Maybe I can clarify this for you a bit. In general, there is no sending of anything TO the GPS satellites.

The GPS satellites send out timing data that your onboard system uses to compute your position, altitude, speed, and direction. It is not a two-way conversation. Think of one satellite like a clock tower that everybody in town can see. There is no limit to the number of people who can read the clock to tell the time, but nobody can talk back to the clock, and the clock doesn't care about you. Like the clock tower, the GPS system has no idea who you are or where you are. There are a bunch of different clock towers / satellites that can be seen from wherever you are, and the differences in time signals you see will depend on your location. It's up to you to figure out your location using those differences. Your GPS receiver does that figuring.

The ADS-B equipment in your aircraft (including a GPS receiver) does all the math after looking at several of those clocks to compute your location information. Then it broadcasts that computed information, with your identifying data, every second, with no need to be pinged by anybody or anything. Its broadcast signal will be picked up by both airborne and ground receiving stations in your vicinity (but it doesn't send anything to the GPS satellites). If there is no ground receiving station in range, your broadcast data does not reach the internet tracking services, but other property equipped aircraft can still see you.

Radar is not involved in the process described above.

Radar interacts with this system only as a supplement. If you are in a region with radar coverage, and you have ADS-B IN, data about traffic that is not ADS-B equipped can be uploaded to you from ground stations in range through TIS-B, using data derived from mode C transponders. This can let you see some nearby aircraft that don't have ADS-B OUT installed.
 
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All_In

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Thanks, Jon. Hope that clarifies it for everyone.

That is what my research showed after your first post.
Also learned what to do if the GPS is not functioning.

I felt it important to let our community know you should not use Flightradar24 as your primary ADS-B IN display.

PS: if you are being pinged from a class B airspace more than likely Flightradar24 has a receiver in your area and you will show up. So far that has been the case.
 
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All_In

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I posted what you do if your ADS-B equipment fails in mid-flight on another thread but will include it here so ADS-B failure rules, I learned, are posted here.

AIM 4-1-20 has some guidance for this situation. It says that “in-flight requests for immediate deviation from the ADS-B Out requirements may be approved by ATC only for failed equipment, and may be accommodated based on workload, alternate surveillance availability, or other factors.” If ATC can’t accommodate your sudden loss of ADS-B out, you’ll need to avoid the airspace where it’s required. If they can, you’re good to go.
 
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Tyger

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I felt it important to let our community know you should not use Flightradar24 as your primary ADS-B IN display.
Or perhaps we can just say that Flightradar24 is not ADS-B In. Full-stop.

Real ADS-B In comes only from the ground broadcast stations.
 

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All_In

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ADS-B Out works by broadcasting information about an aircraft's GPS location, altitude, ground speed, and other data to ground stations and other aircraft in range, once per second. Air traffic controllers and properly equipped aircraft receiving the 1090MHz and or 978Mhz frequency can immediately receive this ADS-B IN information.

Flightradar24 acts as one of the ground station receivers and redisplays any aircraft they can receive on the internet. This leaves many blind spots compared to an ADS-B IN receiver and a dedicated display in the aircraft showing all ADS-B out traffic anywhere near you once a second.
 
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Sv.grainne

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That's my point, the app is pretty worthless for a pilot. ADS-B, aircraft to aircraft is real time, does not require a ground station, does not involve Radar or ATC.
 

Sv.grainne

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Like Marine AIS, people started relying on electronics and stopped using their eyeballs. ADS-B, when in use is great, but if you don't have it, or the approaching AC does not, oh well sports fans!
 

Tyger

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ADS-B does not require a ground station!
Full functionality of ADS-B In does require a ground station "link".
If you want FIS-B, it's coming from a ground station.
If you are using only 978 MHz UAT for your Out, and want to see aircraft that are using only 1090 MHz (or non-ADS-B aircraft that ATC is tracking (TIS-B)), you need a ground station to provide ADS-R. Ground station coverage is now pretty comprehensive in the continental US, at least if you are flying over 1500 ft. In my personal experience, I occasionally lose coverage when flying lower than that, but never for very long...

Any "not-on-the-same ADS-B Link" aircraft that falls within the "hockey puck" will be transmitted via ADS-R on the appropriate ADS-B In link to the "client" aircraft. Similarly, any non-ADS-B Out Transponder equipped aircraft within the "client" aircraft's hockeypuck will be transmitted via TIS-B on the appropriate ADS-B In link.
 
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Tyger

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But AC to AC only works if both aircraft are using the same link frequency for Out (there are two).
 

All_In

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In the United States, ADS-B-equipped aircraft and vehicles exchange information on one of two frequencies: 978 MHz or 1090 MHz.
Mode A/C and S transponders, as well as Traffic Collision and Avoidance Systems (TCAS), use 1090 MHz.

Many manufacturers of ADS-B IN have both frequencies so you will see all ADS-B equipment cockpit to cockpit if you can receive both.

When you receive IN from a ground station it will add TIS-B which includes non-ADS-B equipped aircraft it sees on their radar to your display and other information.
According to the FAA site going through a ground station adds:

Traffic Information Services – Broadcast (TIS-B)​


What it does​


This free service broadcasts relevant traffic position reports to appropriately equipped aircraft. TIS-B information is available to aircraft that broadcast valid ADS-B Out and utilize ADS-B In on 978 MHz (UAT), 1090MHz (1090ES), or both. The aircraft must be within the coverage of an ADS-B ground station and an FAA radar or multilateration system to receive the target information.

To learn more here is one of the FAA pages that describe it.
Here is another that was helpful.
 

All_In

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Note: I've not researched all manufacturer's equipment.
I'm looking for equipment for the AG915 now.
Using my eyes and flight following when I'm high enough over the mountains to be seen with old fashion radar.
With gyros, I fly for the sheer joy of flying = sightseeing at a much lower altitude than FWs so Flight Following seeing us on radar was about as often as Flightradar24 seeing us on their receiver.

However, I suspect, because "Mode A/C and S transponders, as well as Traffic Collision and Avoidance Systems (TCAS), use 1090 MHz."
All the equipment I've looked at was broadcasting only on 1090 MHz or both.
 
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All_In

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Why 978 UAT? If you have a glass cockpit or a modern navigator, a 978 UAT can display subscription-free weather and traffic on those beautiful color screen (if your 978 solution is an ADS-B In model in addition to Out).
 

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FlightAware and ADS-B​


In addition to receiving over 45 different government air traffic control and private datalink sources, FlightAware operates a worldwide network of ADS-B and Mode S receivers that track ADS-B or Mode S equipped aircraft flying around the globe. ADS-B equipped aircraft emit their exact position and Mode S aircraft can be tracked via multilateration (MLAT) when the signal is received by three or more receivers. FlightAware owns and operates these receivers at hundreds of airports around the world in conjunction with airport operators.
FlightAware designs and manufactures FlightFeeder, a network ADS-B receiver that receives ADS-B data and feeds the data to FlightAware's servers over any available Internet connection.
We also invite customers and professional users to connect to FlightAware's network and feed additional ADS-B data from their receivers using the methods described below. ADS-B data contributed is made available on FlightAware's free web site and mobile apps.

Note: These receivers could be temporarily installed at remote locations to augment the system temporarily, but they would require an internet connection.
 

dabkb2

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It is good to have a working understanding of how ADS-B performs. From my perspective flying around Southern CA and hopefully beyond someday, it is a good tool, and flightradar24 might not be as good as ADS-B in. It is better than nothing and either way you have to keep your eyes scanning. Fly Safe.
 

All_In

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It is good to have a working understanding of how ADS-B performs. From my perspective flying around Southern CA and hopefully beyond someday, it is a good tool, and flightradar24 might not be as good as ADS-B in. It is better than nothing and either way you have to keep your eyes scanning. Fly Safe.
LA and San Diego are fully covered by radar on the west side of the mountains and far out to sea.
I suspect Fightradar24 works well with receivers from San Diego all the way to the mountains north of LA.
 

Sv.grainne

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It is good to have a working understanding of how ADS-B performs. From my perspective flying around Southern CA and hopefully beyond someday, it is a good tool, and flightradar24 might not be as good as ADS-B in. It is better than nothing and either way you have to keep your eyes scanning. Fly Safe.
Dave, wasn't knocking you, just general comment. Anything that can help is good.

Bobby
 

dabkb2

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Dave, wasn't knocking you, just general comment. Anything that can help is good.

Bobby
It's all good, Didn't think you were. It seems like I am learning a lot of things all at once.
 
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