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ADS-B TIS-B Client %

tsneidin

Well Known Member
My last flight ads-b traffic worked just fine, today no traffic. I received the ads-b performance report for the flight and it shows that I transmitted ~9700 messages to them, no errors or RED flags on the report at all, SIL=3 etc. The TIS-B Client % field is 0.0%. According to the docs TIS-B Client % is:

TIS-B Client %: Percentage of operation time TIS-B data
was provided to the aircraft by the ADS-B ground
system.

So if everything was reporting correctly why didn't the ground stations provide any data? Traffic showed up for my previous flights and the reports shows TIS-B Client % around 100%.

This flight was in central Wisconsin 12/9/2016
 
Well, if TIS-B was zero, either the ground station was malfunctioning, or there was no traffic to report. Remember they only send up traffic within the 15 nm radius, up/down 3500', hockey puck region. Did you see any traffic within that volume?
 
Yes, assuming you didn't observe any traffic (with eyeballs), it's likely there was no traffic close enough to you to provide TIS-B data for.

Did you see any other aircraft while you were flying?
 
Post the report if you can.. What do you have for IN capabilities configured? It's listed on the report so you can check quickly.. If it's "none" then I suspect they won't send you any traffic data... :)
 
Hello Todd,

First a clarification. Some postings above are saying that the presence of traffic in the area you are flying will affect the "TIS-B Client %" value being reported in this report from the FAA. This is entirely incorrect.

Whether or not the ground stations are providing you with TIS-B client services is strictly between your aircraft, ATC radar, and the ADS-B ground stations and has nothing to do with having traffic in the area. You must be in radar contact and must be a valid ADS-B Out aircraft with ADS-B In capability before the ground stations will declare you a TIS-B client and provide TIS-B traffic (Mode C) uplinks.

Notice that this also applies to whether or not you receive ADS-R uplinks, but since you have a GDL39 dual frequency receiver and don't need any help from the ground stations to see ALL ADS-B Out traffic on both 978/1090 Mhz directly (and they know this from your ADS-B Out messages), they don't provide ADS-R uplinks to you.

The meaning "valid ADS-B Out" aircraft has been a moving target. Aircraft transmitting SDA=0 with non FAR 91.227 compliant position sources used to be able to receive TIS-B client services, but early in 2016 the bar was raised to SDA > 0, which made little sense (prior to 2020 which requires SDA=2), but that is what they did. As you know, FAR 91.227 specifies SDA = 2 (and SIL=3), so raising the bar to provide TIS-B services to aircraft transmitting SDA=1 is only on a temporary condition.

Note that this doesn't have anything to do with you since you are transmitting SDA=3, SIL=3, but we bring this up as history since your SDA=3 is a little unusual. As mentioned above FAR 91.227 doesn't say SDA>= 2, it says SDA = 2.

I just looked at the most recent reports from the two G3X EAB aircraft we fly, and both are transmitting SDA=2, SIL=3. One of them has a GTX345R with built-in GPS position source and the other (our RV-7A) has a GTX 45R with GTN 750 external ADS-B position source.

I also looked at an older report with a GPS20A position source connected to a GTX23ES, and it also transmitted SDA=2, SIL=3.

I don't think think there is a problem with you transmitting SDA=3 and the report shows no problem with this, but it is unusual, so not sure if that is affecting whether or not the ground stations provide TIS-B client services to you.

You mention that your 696 and Garmin Pilot displays agree with this FAA report that you are not receiving TIS-B client services. Good to hear since the ground stations send out a list of ICAO addresses that are receiving TIS-B client services every 20 seconds and the GDL39 looks at this list to verify your aircraft address is in the list before telling the displays that your aircraft is receiving these services. At any point that 2 of these updates pass and your aircraft ICAO address is not in the TIS-B client list, the GDL39 tells the displays you are no longer a TIS-B client.

So, lots of words here to say that you "should" have been receiving TIS-B services as long as you were flying high enough on this 36 min. flight to be in radar contact. Was this the case? This is one of the protections in place to make sure there is little chance of someone spoofing the system. No radar contact, no TIS-B client services provided. You say that Madison was vectoring you for traffic, so it sure seems like you should have been in good radar contact, but since this might have been terminal radar approach control, I don't know if this satisfies the radar contact requirements for ADS-B TIS-B services.

In past years it wasn't uncommon to see "holes" in the system when handoffs between ground stations providing TIS-B services would sometimes fail, but the system seems pretty robust these days. On most of our flights the TIS-B Client % is close to 100%.

Thanks,
Steve
 
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Thank you Steve

Thank you for that helpful explanation. I was flying 2000agl, squawking a discrete transponder code while receiving vfr traffic advisories from MSN approach. At the end of the flight I specifically asked the controller if my transponder was dropping or weird in any way and he replied that it appeared to be working perfectly.

The position source for my Trig Tt-31 is the garmin GPS 20A that I recently installed. I have reports from previous flights where I received traffic perfectly and the SDA was equal 3.
 
Thank you for that helpful explanation. I was flying 2000agl, squawking a discrete transponder code while receiving vfr traffic advisories from MSN approach. At the end of the flight I specifically asked the controller if my transponder was dropping or weird in any way and he replied that it appeared to be working perfectly.

The position source for my Trig Tt-31 is the garmin GPS 20A that I recently installed. I have reports from previous flights where I received traffic perfectly and the SDA was equal 3.

When I run into intermittent problems, I usually go back through every configuration step, and check the mechanical / electrical connections. I looked at the Trig TT31 manual for compatible GPS sources, and noted that the GPS20A has not been tested (that doesn't mean it won't work.) The GPS20A operates at 9600, I'd check to verify that speed is configured in the Trig. I'm assuming you configured the protocol as Garmin ADSB+. Have you checked if the connectors are tight on each unit, and the pins are properly seated? Are you using an approved GPS antenna and the appropriate RG cable and length?

Also possibly relevant items to configure noted in the Trig manual:

6.1.9.1 GPS System Certification Level
Issue AP
An important metric for ADS-B ground system behaviour is the SDA or System Design Assurance level. It is intended to reflect the probability that the GPS position source is providing erroneous information, and is based on the certification standard that was used by the GPS vendor. This will be indicated in the form of a letter code (A to D) on the data plate or installation documentation for the GPS in accordance with the standards DO-178B and DO-254, for example “DO-178B level C”. If both standards are reported but at different levels, use the lower standard (higher letter).


6.1.9.5 ADS-B Receiver Options
In the USA there are two ADS-B channels, 1090ES and UAT, and there is an ADS-B based traffic information service called TIS-B. The ADS-B ground stations relay this information between the two channels so that suitably equipped aircraft can receive traffic information. To limit channel congestion these services are only provided to aircraft equipped to receive them.
The transponder reports what receivers are installed in a periodic status message; enter the receiver status here.

6.2.5 RS232InputCheck
The RS232 interface check provides a diagnostic that the RS232 input lines are configured correctly. It will display on screen the data each RS232 line is set up to receive. If valid data of the correct type is being received, the decoded data will be shown on the display.

Post Install test:

Where installed, verification of the GPS position source and ADS-B outputs. In an aircraft with a configured GPS, pressing the FUNC button on the transponder front panel in normal operation will display the ADS position monitor. With the aircraft outside the hangar (for good GPS reception) the aircraft position should be displayed on the transponder. If the position indications are all dashes then either the GPS position is not valid or the GPS interface is not correctly configured. Whenever a valid position is received by the transponder and the transponder is in any mode other than Standby, ADS-B Extended Squitters should be observed on the transponder test set.
 
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This is one of the protections in place to make sure there is little chance of someone spoofing the system. No radar contact, no TIS-B client services provided.

This bit of info seems important. Does this also apply to ADS-R (so my 978-only receiver can see 1090ES targets and vice-versa), or just TIS-B (sourced from radar)? I'm often dropped from radar flying at 2k' AGL away from the larger airports, it would be a shame to lose the traffic picture at the same time, only receiving same-band air-to-air targets.

With many installations taking the 1090ES-Out route thanks to solutions like the GTX 45/345/etc, Dynon, and Trig, it seems that dual-band receive is perhaps more important than was predicted a few years back, when the expectation was that the "majority of light GA will use 978 UAT." Unfortunately the few solutions that will integrate with my older EFIS are not dual-band.
 
This bit of info seems important. Does this also apply to ADS-R (so my 978-only receiver can see 1090ES targets and vice-versa), or just TIS-B (sourced from radar)? I'm often dropped from radar flying at 2k' AGL away from the larger airports, it would be a shame to lose the traffic picture at the same time, only receiving same-band air-to-air targets.

With many installations taking the 1090ES-Out route thanks to solutions like the GTX 45/345/etc, Dynon, and Trig, it seems that dual-band receive is perhaps more important than was predicted a few years back, when the expectation was that the "majority of light GA will use 978 UAT." Unfortunately the few solutions that will integrate with my older EFIS are not dual-band.

Hello Joshua,

Yes, to quote the FAA service change document "In the FAA system, ADS-R client status is identical to TIS-B client status", so the posting above could have referred to "TIS-B/ADS-R client status" in every place it refers to TIS-B client status.

Good or bad, the U.S. is a dual frequency country with some ADS-B Out aircraft transmitting on 978 Mhz and some on 1090 Mhz, which makes it important to have a dual frequency ADS-B receiver.

The latest FAA equipage report shows that more than 70% of the aircraft which have equipped for ADS-B Out have equipped with a 1090 Mhz transmitter and there is strong evidence this trend will hold or increase.

Thanks,
Steve
 
So, lots of words here to say that you "should" have been receiving TIS-B services as long as you were flying high enough on this 36 min. flight to be in radar contact. Was this the case? This is one of the protections in place to make sure there is little chance of someone spoofing the system. No radar contact, no TIS-B client services provided. You say that Madison was vectoring you for traffic, so it sure seems like you should have been in good radar contact, but since this might have been terminal radar approach control, I don't know if this satisfies the radar contact requirements for ADS-B TIS-B services.

Steve,
Lots of good information here! ADS-B seems like it should be 1/4 of ground school today.

It's my understanding that the reason TIS-B and ADS-R services are not provided to aircraft without radar contact is to prevent the pilot from thinking they have a complete traffic picture when they do not. If the ADS-B system can't see you on radar, then there's no reason to believe it can see the aircraft that is a threat to you either. So while they don't send out TIS-B and ADS-R, they also importantly don't send you the client status bits so your cockpit display can warn you of the incomplete picture so you don't rely on the traffic display too much.

Another bump we've run into at Dynon before- data links being down to ADS-B ground stations. There was one in Tucson that was down for 9 months because the link to the ground station was severed, but the tower was still "online," transmitting that it was fine. It just wasn't transmitting any FIS-B data or TIS-B, which of course meant that you were never a TIS-B client because it had no radar link to see you on. This caused all sorts of weird behavior.

All this to agree that there are external issues which can cause TIS-B service issues, which have nothing to do with your plane. Which is why it's important that your cockpit traffic display shows if you are a TIS-B/ADS-R client. On Dynon this is "ADS-B OK" and on the Garmins this is the radar icon being present.

--Ian
Dynon Avionics
 
Fixing SDA did not fix the issue

I did have GPS certification level set to Level D for all my previous flights. Last night I changed it to Level C (the proper value) and went flying.

Here is the ADS-B performance report for the flight.

https://drive.google.com/open?id=0B8AN0FyM0qDlQTZ5d1ZoZi1KR1JXcGF6RGpFZ05OUFVUcHl3

It now shows the correct SDA=2 value and no errors but again I received no traffic and 696 and Garmin pilot did not display the correct symbols.
 
I did have GPS certification level set to Level D for all my previous flights. Last night I changed it to Level C (the proper value) and went flying.

Here is the ADS-B performance report for the flight.

https://drive.google.com/open?id=0B8AN0FyM0qDlQTZ5d1ZoZi1KR1JXcGF6RGpFZ05OUFVUcHl3

It now shows the correct SDA=2 value and no errors but again I received no traffic and 696 and Garmin pilot did not display the correct symbols.

Hello Todd,

We didn't expect that changing the SDA to 2 would change anything since the current minimum required for TIS-B services is SDA=1, but good to know, so thanks for trying that.

You say that "696 and Garmin Pilot did not display the correct symbols". Not sure what that means, but since your report indicates you were a TIS-B client 0% of the flight, it would have been correct for the 696 to show that you were not receiving TIS-B uplink data on this flight.

You might contact our friend at the FAA, Jim M. and see if he can provide any additional information for this flight which might explain why the ground system was not providing you with TIS-B services. He may have access to this information.

Thanks,
Steve
 
G3X Config Issue?

g3xpert Steve,
I have a newly installed G3X Touch, GTX-23ES and GDL-39R with a GTN 650. I recently flew a flight for the FAA ADS-B Rebate program and I failed the SDA and SIL 100% with values of 0.0. My report says I also was TIS-B Client 0%. I believe this is because I did not configure the G3X to enable the external GPS at power up. I assume then the failure was because it used the internal GPS to the GDU 460. I have not been receiving any ADS-B weather or traffic. If I understand this correctly I need to select the external GPS (GTN-650) in the configuration for startup and I should see weather and traffic services when in radar contact.
Thanks!
Kent
 
g3xpert Steve,
I have a newly installed G3X Touch, GTX-23ES and GDL-39R with a GTN 650. I recently flew a flight for the FAA ADS-B Rebate program and I failed the SDA and SIL 100% with values of 0.0. My report says I also was TIS-B Client 0%. I believe this is because I did not configure the G3X to enable the external GPS at power up. I assume then the failure was because it used the internal GPS to the GDU 460. I have not been receiving any ADS-B weather or traffic. If I understand this correctly I need to select the external GPS (GTN-650) in the configuration for startup and I should see weather and traffic services when in radar contact.
Thanks!
Kent

Steve should be along shortly but the bottom line is you will need to work with TeamX to get this ironed out. What you are describing is not normal and I am almost certain it does not relate to the navigation source selection option on power up. I recommend you email them ASAP to get the ball rolling on troubleshooting. [email protected]
 
g3xpert Steve,
I have a newly installed G3X Touch, GTX-23ES and GDL-39R with a GTN 650. I recently flew a flight for the FAA ADS-B Rebate program and I failed the SDA and SIL 100% with values of 0.0. My report says I also was TIS-B Client 0%. I believe this is because I did not configure the G3X to enable the external GPS at power up. I assume then the failure was because it used the internal GPS to the GDU 460. I have not been receiving any ADS-B weather or traffic. If I understand this correctly I need to select the external GPS (GTN-650) in the configuration for startup and I should see weather and traffic services when in radar contact.
Thanks!
Kent

Hi Kent,

No, you don't need to configure the G3X to select or enable the external GPS at power-up. As long as the GTN 650 is turned on and operating with a good GPS fix and the ADS-B+ RS-232 output is properly connected to pins 24,50 of the GTX 23ES (page 24-19 or Rev. AA G3X Installation Manual), the GTN will be providing GPS position to the transponder.

Additionally, please make sure that the Position Integrity field on the transponder configuration page is set to "1E-7" instead of "VFR" as shown on page 32-129 of the Rev. AA G3X Installation Manual. This would indeed cause what you describe to happen. While you are in there, make sure that ALL transponder configuration fields (such as airplane width) are filled in.

Let us know if you have additional questions.

Thanks,
Steve
 
to quote the FAA service change document "In the FAA system, ADS-R client status is identical to TIS-B client status", so the posting above could have referred to "TIS-B/ADS-R client status" in every place it refers to TIS-B client status.

Good or bad, the U.S. is a dual frequency country with some ADS-B Out aircraft transmitting on 978 Mhz and some on 1090 Mhz, which makes it important to have a dual frequency ADS-B receiver.

ADS-B seems like it should be 1/4 of ground school today.

It's my understanding that the reason TIS-B and ADS-R services are not provided to aircraft without radar contact is to prevent the pilot from thinking they have a complete traffic picture when they do not. If the ADS-B system can't see you on radar, then there's no reason to believe it can see the aircraft that is a threat to you either.

I thought I had a pretty good handle on ADS-B and a couple different plans for equipment, but this was new info to me -- I'm certainly learning, thanks to you guys for sharing.

So for those of us who are regularly out of radar coverage due to terrain, altitude, or other factors, the dual-band receive is going to be an important thing if we want to have the most traffic assistance as possible. Ian, are there plans afoot to produce a dual-band Dynon/AFS receiver module to fill this gap? Unfortunately the new GTX boxes all omitted the legacy protocols that would allow traffic to feed older EFIS's; I even looked at adding a GDU370 just for mapping & traffic/weather, but the GTX won't feed those either (without the 39R).

Freeflight is rumored to have a dual-band unit in the works, but they did not respond to my request for additional information.
 
So for those of us who are regularly out of radar coverage due to terrain, altitude, or other factors, the dual-band receive is going to be an important thing if we want to have the most traffic assistance as possible. Ian, are there plans afoot to produce a dual-band Dynon/AFS receiver module to fill this gap? Unfortunately the new GTX boxes all omitted the legacy protocols that would allow traffic to feed older EFIS's; I even looked at adding a GDU370 just for mapping & traffic/weather, but the GTX won't feed those either (without the 39R).

Freeflight is rumored to have a dual-band unit in the works, but they did not respond to my request for additional information.

I bought a factory overhauled SkyRadar D2 for $500. Dual band. Feeds GRT HX via USB, iPad (WingX) via WiFi. Works great using internal antennas on the fiberglass doorposts of the -10.
 
May I revive this old thread? I just installed a Garmin GDL-82 and it seems to be working as advertised, but my "TIS-B Client Percentage" has been in the 20% to 50% range. On my latest flight, I was out of radar contact for a few minutes, so that probably explains it. (I thought the whole idea of ADS-B was that you no longer needed ground-based radar, but that doesn't seem to be the case.) In my area, there is only a single low-powered ground station, surrounded by mountains, so that is probably another factor. Steve's explanation (above) was very helpful in understanding how the system works, but I still have some questions: Is my GDL-82 transmitting to the radar facility, a ground station, other UAT-equipped aircraft, or all of the above? Steve wrote earlier that "the ground stations send out a list of ICAO addresses that are receiving TIS-B client services every 20 seconds". How does an aircraft get on that list? When I'm taxiing for takeoff at KAVL, I seem to be receiving traffic from somewhere, although I'm out of range of the nearest ground station. Does ATC radar at KAVL put me on "the list", or do I have to wait until I'm airborne and in range of the ground station? If my transponder antenna was weak or poorly placed, could that cause a low Client percentage? Speaking of transponder antennas, mine was cut for the original 1090 MHz output of my Garmin GTX-327. Should I have replaced it with a 978 MHz antenna which is around 10% longer?
 
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more information

I'll have to try this next time I'm up. From the Foreflight website:
When you tap on a traffic target while using a Stratus ADS-B receiver, you will get an information pop-up. In the description, you may see the frequency band used (978 or 1090ES) followed by "ADS-B", "ADS-R", or "TIS-B".

When "ADS-B" is shown in the description it indicates that the information was obtained via Air-to-Air broadcast, which is a direct broadcast from an ADS-B Out-equipped aircraft.

When ?ADS-R? is shown in the description, it indicates that the ground station re-broadcast the ADS-B message it received on the other ADS-B frequency. This is a service provided to client aircraft that indicate they do not have a dual frequency receiver.

When "TIS-B" is shown in the description it indicates that the information was obtained via broadcast from a ground station. Ground stations provide the TISB service for ADS-B Out-equipped client aircraft. The TISB target is not ADS-B Out-equipped and is detected by a secondary radar system. All TISB targets must have an operating mode C transponder.
 
May I revive this old thread? I just installed a Garmin GDL-82 and it seems to be working as advertised, but my "TIS-B Client Percentage" has been in the 20% to 50% range. On my latest flight, I was out of radar contact for a few minutes, so that probably explains it. (I thought the whole idea of ADS-B was that you no longer needed ground-based radar, but that doesn't seem to be the case.) In my area, there is only a single low-powered ground station, surrounded by mountains, so that is probably another factor. Steve's explanation (above) was very helpful in understanding how the system works, but I still have some questions: Is my GDL-82 transmitting to the radar facility, a ground station, other UAT-equipped aircraft, or all of the above? Steve wrote earlier that "the ground stations send out a list of ICAO addresses that are receiving TIS-B client services every 20 seconds". How does an aircraft get on that list? When I'm taxiing for takeoff at KAVL, I seem to be receiving traffic from somewhere, although I'm out of range of the nearest ground station. Does ATC radar at KAVL put me on "the list", or do I have to wait until I'm airborne and in range of the ground station? If my transponder antenna was weak or poorly placed, could that cause a low Client percentage? Speaking of transponder antennas, mine was cut for the original 1090 MHz output of my Garmin GTX-327. Should I have replaced it with a 978 MHz antenna which is around 10% longer?

TIS-B client: low percentage indicates you were often out of contact with a ground station.
Your -82 signal is designed to be received by other aircraft who are listening on 978MHz, and ground stations.
Imbedded in your “out” data stream is your ICAO address. I don’t know what the system does if you’re in anonymous mode. If you change your squawk to anything other than 1200 (e.g., getting radar advisories) anonymous mode is automativally turned off.
If you have a weak or poorly placed antenna you most likely will fail the airborn test, and the biennial transponder test.
If you are using the -82 as designed (sharing one antenna with the ADSB and transponder) keep the transponder antenna. The 82 is designed to live with the small mis-match.

Edit. You don’t say what you’re using for ADSB-in. The -82 must be configured to tell the ground station if you have receive capability on 978, 1090, or both.
 
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TIS-B client: low percentage indicates you were often out of contact with a ground station.
I'm using Stratus 2 / Foreflight / iPad as my "in" setup. I have the 978 and 1090 "receive" parameters in the GDL-82 both set to "capable" so I think I'm set up correctly. My iPad shows that I'm receiving data on both channels. The only ground station in the entire area is 12 NM S of my home airport and it's "Low-tier" so reception on the ground is "marginal".

I guess one thing I don't understand is how my outgoing sqawks get into "the ADS-B system". I had it in my head that there were three paths:

1. Via ATC radar
2. Via a ground station [GBT]
3. Indirectly via air-to-air with another UAT-equipped aircraft.

Our G3Xpert (Steve) posted earlier that I wasn't a TIS-B "client" unless I was in radar contact. I'm having difficulty with that concept because the whole idea of "NextGen" was "free flight" whereby ATC would know where aircraft were in areas of no radar coverage. Of course the FAA computers might know where I am but that doesn't mean they will send traffic info back to me. So is the system set up to cut me off from traffic data when I'm out of radar contact - the very time that I need the traffic information the most?

On a recent 20 min. flight GMU==>AVL at 4,500', I was out of radar contact for 5 minutes because I was low. But FlightAware showed my total ground track so the "ADS-B system" knew my position and altitude all along. I'm pretty sure, though, that ATC doesn't yet use a readout of our ADS-B data. I asked one of the controllers at AVL if he could tell if my ADS-B (out) was working. He said "we have that on a separate screen but I'll go check". Apparently he had to get up out of his station and go look.

It seems that my (out) system is working fine, but I just need to understand how much I can trust the traffic (or lack of traffic) I'm seeing on my iPad. Next time I fly (which may be over a week due to rain), I'll investigate further.
 
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I captured some screen shots today. I pulled my plane out of the hangar so the GPS had a view of the sky. My hangar is probably 200' from the rotating radar antenna so I suppose I was in "radar contact". I was 12 miles away from the ADS-B ground station and my signal strength was showing "Marginal". My iPad was showing several targets, and I tapped on each one to reveal the source. Two of the targets reported the source was "1090 ADS-B" and one reported "978 TIS-B". After Citation N975MD landed, I went up to the Captain and asked him what type of transponder he had. He told me it was all integrated and probably a Collins. He knew it was 1090ES and thought it might also broadcast on 978. My iPad said he was on 1090ES. These screens probably bring up more questions than they answer, but here they are:

zj5s21.png


wYlNm9.png


MvEZ8r.png


jOCqH5.png
 
had it in my head that there were three paths:

1. Via ATC radar
2. Via a ground station [GBT]
3. Indirectly via air-to-air with another UAT-equipped aircraft

r.

1. There are a small number of ATC radar sites that send traffic to those with a mode S transponder. But that’s not you, you get nothing directly from atc radar.
3. I would say directly, not indirectly, you get traffic info from other aircraft with either a UAT (978 MHz) or an S-ES transponder (1090 MHz).
2. The ground stations are fed traffic that ATC radar is seeing (whatever they see, regardless of formal radar contact. Many vfr targets will have no N number data because the radar does not know it.), as well as adsb aircraft that they are receiving signals from. The ground station will filter out all the targets that have adsb-out, both 978 and 1090, because you told it that you could receive those directly. The remaining radar targets will be sent to you if they are within 15 miles horizontally and 3000’ vertically.
You may frequently get data outside that area, if you intercept a ground broadcast intended for another airplane.

You still need to look. When you are going into a small airport below radar coverage, ADSB will be unable to show you any aircraft who do not have adsb-out.

Your Citation captain doesn’t know his equipment. Per the FARs one plane can listen on both frequencies, but may not transmit on both. Too much confusion. And since jets almost always go above 18,000’, they will have 1090SES for adsb out.
 
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1. There are a small number of ATC radar sites that send traffic to those with a mode S transponder. But that’s not you, you get nothing directly from atc radar
I'm mulling that over. While sitting on the apron in front of my hangar today, somehow ATC knew I was there as indicated by the "Ownership: Detected N10CF" in the screen shot above. So you're saying they didn't recognize me through the ATC Radar tower 200' away. How, then?

Aside: Did you know Ed Williams at Livermore?
 
I'm mulling that over. While sitting on the apron in front of my hangar today, somehow ATC knew I was there as indicated by the "Ownership: Detected N10CF" in the screen shot above. So you're saying they didn't recognize me through the ATC Radar tower 200' away. How, then?

Aside: Did you know Ed Williams at Livermore?

Unless you have a mode S transponder, all radar knows is your squawk code and altitude (and location). It looks to me like you have received info from a ground station.
I worked with Ed at Livermore Lab for many years. He and I, and a third person, were partners in a 182 for 20 years. He?s retired now, living in Maui, HI. Last December he had a mild heart attack, I don?t think he?s been flying for some years now.
 
It looks to me like you have received info from a ground station.
That's possible. I'm just trying to figure how this all works. I'm pleased that you worked with Ed. Small world. He and Marlene had me over to their house in Berkeley for supper once. I haven't spoken to him for many years, but use his Formulary quite often.
 
I just installed a DeltaPop blade-type transponder antenna to replace my Archer SA-005 and am very pleased so far. My "radar contact" was much better over the mountains and my ADS-B Client % was 46% - not bad considering that there were no ground stations in the area where I was flying.
 
I'm still trying to understand how all this works. I went up today and stayed in the "practice area" just outside the AVL Class C. I was with Approach the whole time at 4,500', just circling around and admiring the scenery. There was a non-equipped C-172 in the same general area at approximately the same altitude, but nothing showed on my "Target" screen (iPad). I was very close to an ADS-B ground station, and Foreflight showed "Good Signal" from the ground station. After about ten minutes of Approach de-conflicting the two of us, the Skyhawk reported climbing to 6,000' so Approach wouldn't have to work so hard. About that time, the C-172 showed up as a target on my screen. I tapped on the target and it said "TIS-B" with no N-Number (of course, since he wasn't equipped). We were both in radar coverage the whole time, so why the delay in TIS-B uplinking him to me?
 
There was a non-equipped C-172 in the same general area at approximately the same altitude, but nothing showed on my "Target" screen (iPad) . . . We were both in radar coverage the whole time, so why the delay in TIS-B uplinking him to me?

How close was he to you when he was not showing on the screen? Within 15 miles? And just to be sure, do you have ADS-B Out working in your aircraft?
 
How close was he to you when he was not showing on the screen? Within 15 miles? And just to be sure, do you have ADS-B Out working in your aircraft?
Approach called him at 3 miles, 1 O'clock, same altitude. He was well within the "hockey puck". Yes, I have a Garmin GDL-82. It seemed to me like there was a ~10 minute latency before the ground station decided to send me the target. I really can't trust this system.
 
In thinking this over, I didn't "see" the target because either I wasn't an ADS-B "client" or he wasn't a "target". After the flight, I requested a "performance report" and my TIS-B client percentage was only 11% for some reason. That had to be because I wasn't in contact with the ADS-B ground station, I wasn't in radar coverage, or something else? The C-172 only became "visible" on my screen when he climbed from 4,500' to 6,000'. It's hard to know whether the problem was mine or his because Foreflight/Stratus doesn't make use of the "Service Status" messages being broadcast which confirm whether your aircraft is a client. Garmin displays an icon on the screen that indicates you are a TIS-B client. It's very disappointing that Foreflight doesn't do this. As a result, when using Foreflight, I never know whether I am seeing the whole traffic picture. From Source: http://adsbforgeneralaviation.com/w...SBS-Description-Doc_SRT_47_rev01_20111024.pdf
The SBSS [Surveillance and Broadcast Services System] control station monitors the ADS-B received reports to identify TIS-B Client aircraft. In order to be considered a TIS-B Client, an aircraft must be ADS-B-OUT, must have produced valid position data (see ?3.3.1.2.5) within the last 30s to a SBS ground station, must be under surveillance of at least one secondary radar and must be ADS-B-IN on at least one link. Two key safety benefits for requiring TIS-B Clients to transmit ADS-B-OUT is spectrum conservation by the SBS [Surface-Based System? - Ground Station?] system and the provision of the TIS-B Service Status message by the SBS system to indicate service availability for specific aircraft.
That ?3.3.1.2.5 (above) requires that your ADS-B (out) position be verified by another source, usually radar. This is why you have to be both in contact with an ADS-B ground station AND within radar coverage to become a "client". Strange, but true. I guess I need to call the TRACON and query them on radar coverage in the area in which I was flying.
 
More info

I called the AVL TRACON this morning and had a productive discussion with one of the senior controllers. She told me that radar coverage was "problematic" below 5,000' in the area where I had been flying. I am convinced that is why I was an ADS-B client for only 11% of the flight. She also mentioned that the only ADS-B ground station in our area is very unreliable and is out of service every couple of days. Maybe that could be a contributing factor as well. I flew again today (in a different area) and my client percentage was up to 38%. I guess that's progress /sarc
 
I've been flying with ADSB for 5 years. Up until recently, there was no TIS-B traffic data in the Asheville valley. The traffic had to be at or above the mountains to our south or southeast in order for TIS-B to work. Obviously a radar line of sight issue.

I have noticed TIS-B data in the valley recently but I agree it is flakey as of yet.

My last social visit to the tower included them showing me the 'Fusion' system screen in the approach room that was due to go online soon. My understanding is that new system will better use ADSB info.


ALSO. I have seen a few comments about the size of the TIS-B data airspace 'puck'of 15 NM. I commonly see data from craft that are 50 miles away such as the buzz of craft in KCLT Class B as I pass by outside the B, or targets near KGSO when that is 80 NM into the future.

Sup wit dat?
 
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...the 'Fusion' system screen in the approach room that was due to go online soon.
That's some good information right there. When I spoke with Kim yesterday, she mentioned "new equipment". Maybe that's what she was talking about. I think you're right about the spotty radar coverage over the mountains, but I have a plan to confirm whether that's the source of my problem. Today I'm flying over the SE practice area again, but at 7,000' this time rather then 4,500'. Hopefully I'll see some TIS-B targets but it doesn't really matter. When I get home I'll request a Performance Report and see what my Client % was. (Aside: When I flew to GMU at 5,500' yesterday, my Client % was 48%.)

As for the distant targets you're seeing, Foreflight has an option to "Hide Distant Targets". You probably have something similar in whatever software you're using.
 
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Q.E.D.

I went up today to the same area as two days ago but flew at 7,000' vs. 4,500'. My TIS-B client percentage was 69%, up from 11%. So as far as I'm concerned, the low-client-percentage mystery is solved. To get better TIS-B, you need better radar coverage. While up there I asked Approach if his "Fusion" system was operational and he said it was. He can now see ADS-B information on his screen as well as radar. He told me as far as he could tell, my ADS-B was working normally. I don't know exactly what his screen shows, but I'm happy now. I should have asked him if he could tell whether I was a Client or not.
 
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ADS-B Test Report

Good afternoon,

I submitted to the FAA for the test report and looks like i have passed all but two areas in the Integrity and Accuracy category. I know that's an important section but I was wondering what is the resolution?

The report came back with:

Avg:

NIC = 9.0
NACp = 10
NACv = 2.0
SIL = 0.0
SDA = 0.0


The red are the failure points.

I know what the definitions of SIL and SDA are but do not know what would be done to correct the issue and pass those two areas.

my setup is a GTN650 and the GTX23

Any ideas?

Ron
 
Good afternoon,

I submitted to the FAA for the test report and looks like i have passed all but two areas in the Integrity and Accuracy category. I know that's an important section but I was wondering what is the resolution?

The report came back with:

Avg:

NIC = 9.0
NACp = 10
NACv = 2.0
SIL = 0.0
SDA = 0.0


The red are the failure points.

I know what the definitions of SIL and SDA are but do not know what would be done to correct the issue and pass those two areas.

my setup is a GTN650 and the GTX23

Any ideas?

Ron

Hello Ron,

Since you have a GTX 23ES transponder, you must have a G3X or G3X Touch system.

Make sure that the Position Integrity is set to "IFR GPS 1E-7" on the transponder configuration page if you are using your GTN 650 as the position source for the GTX 23ES. Also, make sure your transponder type is set to GTX 23ES, not GTX 23.

Thanks,
Steve
 
Hello Ron,

Since you have a GTX 23ES transponder, you must have a G3X or G3X Touch system.

Make sure that the Position Integrity is set to "IFR GPS 1E-7" on the transponder configuration page if you are using your GTN 650 as the position source for the GTX 23ES. Also, make sure your transponder type is set to GTX 23ES, not GTX 23.

Thanks,
Steve

Thanks Steve,

You are right....It is the GTX 23ES and the transponder is set to that. And yes, it is the G3X non-touch to the GTN650.

I will check the transponder configuration page to ensure it is set to "IFR GPS 1E-7".

Thank you for the guidance.

Ron
 
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