I’ve had my UAT receiver up for roughly a week now and recently changed over to the orange flightaware dongle. Doing so my range doubled and at times can see aircraft on UAT anywhere to 75-100 miles in each direction. I’ve noticed i’m picking up a lot of “TIS-B” traffic and wondering how this is different then UAT. From my research I’m less than 10 miles (as the crow flies) from a TIS-B Tower located in Kenly, NC. Can I assume i’m seeing traffic being rebroadcasted by this tower since the TIS-B traffic comes and go’s throughout the day?
FWIW I’ve also been picking up F15e Fighter Jets from Seymour Johnson AFB on TIS-B
Yes, TIS-B is from a ground station. This is traffic data sent for conspicuity reasons so that 1090MHz aircraft are visible to aircraft that only have 978MHz in. You’ll typically see two types of TIS-B:
data from an aircraft with 1090MHz ADS-B out, e.g. N22593 in your screenshot, being rebroadcast by the ground station on 978MHz (i.e. ADS-R)
radar tracks e.g. all the 278xxx addresses (note the italics - these are not ICAO addresses)
In theory Mode S radar tracks could turn up as TIS-B with an ICAO address, but in practice this doesn’t seem to happen, they turn up without the ICAO address.
TIS-B is usually only sent when there’s something around to hear it (i.e. something nearby with 978 in + out).
Yes I get “big” aircraft showing up with proper data on UAT, I’ve identified several helicopters and a few smaller commercial aircraft that are running dual ADS-B and UAT out. What is interesting is I usually pick up the UAT beacon at a lower altitude then I do 1090 ADS-B.
My 978 UAT system has been active much of this year. It shows traffic out to tens of miles for low flying aircraft and occasionally beyond 100 nmi for higher-flying planes.
What I rarely see is TIS-B data from the local ground station(s), one of which is within line-of-sight about 6nmi away. When I do get TIS-B it is a solid data stream.
The TIS-B is rebroadcast data for aircraft which have only UAT for ADS-B in. I have read the rebroadcast is only for aircraft in the vicinity of the UAT-only airplane.
Is there any way to identify which airborne UAT source is the “trigger” for the TIS-B rebroadcast?
In this screen shot there’s only one likely airborne “trigger” aircraft. It is categorized as “other.” But it is too far away to justify the on-ground airplanes.
There’s nothing in the transmitted messages that would identify the triggering aircraft. The exact details of the decision about what TIS-B to send are fairly opaque - it’s whatever the FAA’s ground systems decide to send. Possibly you just can’t see the triggering aircraft directly.
[…] using the client’s ADS-B Out position information it creates a “hockey puck” around the aircraft. The “hockey puck” is 30 nm in diameter and +/- 3,500 ft. 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” aircrafts hockeypuck will be transmitted via TIS-B on the appropriate ADS-B In link.
(In the above example, if you’re considering AD3F30 as the possible trigger, this seems unlikely to be a direct transmission - it’s 100NM away at 1000ft, I doubt you can hear that directly - possibly it’s skyaware mis-coloring what was received and that’s actually ADS-R)
