Why 'No Radar' for ADSB status

[jmurtagh13]

Question: What are the circumstances that generate the ADSB status “No Radar” when several ground stations are in range and the SV-470 is receiving from these stations? This happens in the Atlanta area when flying at 1000’ AGL or less. I could not find anything in the ADS-B specification indicating a “No Radar” status.

From the Dynon documentation it states the ground station is not able to convey a full traffic picture, again why if I’m in range of at least 5 stations?

From the Dynon SV user manual;
SkyView will annunciate “No Radar” traffic when it has ADS-B reception capability, but that ADS-B reception does not include either ADS-B ground station coverage or radar targets included within those ground-based ADS-B traffic reports. Therefore, the ADS-B ground station is not able to convey a full traffic picture and cannot make you aware of all possible detectable traffic.

Thank you

John

 

[dynonsupport]

This means you're in an area where your plane cannot be seen on radar. Because your plane cannot be seen on radar, the system assumes that the plane next to you which is a threat also can't be seen on radar. Since only about 10% of planes are ADS-B equipped, without radar it means you're missing 90% of traffic, and this is a warning that the traffic picture is very incomplete.

This has nothing to do with how many ground stations you can see. The ground stations aren't radar stations, they just uplink traffic from radar stations. The ground stations specifically send up a message to your plane telling you if they believe you have full coverage or partial coverage ("TIS-B Client service status") and we indicate that with the "OK" or "NO RADAR" states. The system will still provide you with any targets it does know about, but many are likely to be missing.

 

[rogersmart]

This is a perfect example why Dynon needs to work on making the receiver dual band. I love the Dynon ADS-B when I receive a ground station, but I don't like my buddy sitting next me with 1090 targets on his Ipad that I don't see when out of range of a station, or as I found out on this thread today, I am out of range of radar. I will pay for the upgrade, please Dynon, put it on the list. If it is on the list, let us know so we will quit asking.

 

[Dynon]

It's definitely on the list!

 

[rogersmart]

Thanks, won't say another word....

 

[dynonsupport]

Remember that a dual-band receiver doesn't pick up all transponder equipped planes, only those with ADS-B. So anytime you are NO RADAR you'll be missing 90% of aircraft, just like a single band receiver.

The only advantage to dual band is in the cases where you're in a place where you also don't have ground station coverage, and in that case you'll be missing 90% of planes instead of 95%.

All of this will get better as more planes equip however and clearly that will be the case as we rush towards 2020.

 

[jmurtagh13]

Thank you for the very quick response. So that's what I though. But radar coverage in the area I was flying shows from the FAA web site good down to 500 feet and when I call Atlanta approach they see me. So I assume SV is not making this determination of No Radar but getting this status from the ADS-B feed correct? And if so is it only my plane the ground station is looking at to send the No Radar status could it be other planes with ADS-B even lower in my puck of traffic not showing on radar? I also have a GDL39 in the plane and it continues to show traffic with no indication that i've noticed of the No Radar warning. Also even though the SV 470 is saying No Radar all traffic seems to still be displayed on the screen.

Thank you again for helping me learn something new.

John