Are you sure that one or the other wasn’t an ADS-R rebroadcast from a ground station?
Address: XXXXXX (ICAO address via ADS-B)
… which in this case the 1090MHz message would be the retransmission, if it was a retransmission.
(Edit: at least I think that a retransmission on 978MHz would show up as “ICAO address via TIS-B” …)
Neither of the dump feeds were italicized. I have the raw data from the 978 decode but was not capturing the 1090 at the time so I can’t go back and check it. I have seen retransmissions show up on both feeders as italics. At any rate, I would not expect a twin jet cessna to frequently fly down low in UAT978 “GA” space…
Cheers!
LitterBug
Italicized flights are something different: they are TIS-B reports of radar tracks where there is no ICAO address available. So the address given is a ground-generated track ID, not a real ICAO address (and that is why dump1090 et all shows them differently - to highlight that they’re not really data from the aircraft and that it’s not a valid address).
In UAT this is the difference between address types of “ICAO address via {ADS-B,TIS-B}” and “TIS-B track file address”.
In 1090ES non-ICAO addresses can show up some (but not all) ES/NT messages:
DF18 CF=1 “Reserved for ADS-B for ES/NT devices that use other addressing techniques in the AA field”
DF18 CF=2 “Fine position TIS-B message” with IMF bit = 1
DF18 CF=3 “Coarse TIS-B airborne position and velocity” with IMF bit = 1
DF18 CF=5 “TIS-B messages that relay ADS-B Messages using anonymous 24-bit addresses”
DF18 CF=6 “ADS-B rebroadcast using the same type codes and message formats as defined for DF=17 ADS-B messages” with IMF bit = 1
(yes it’s all horrible - took me the best part of a day to untangle the specs there)
Rebroadcasts between 978MHz and 1090MHz are probably always going to show up with a valid (no italics) ICAO address as the address from the original message is included in the rebroadcast.
(For UAT → 1090ES this will be a DF18, CF=6 message with IMF = 0)
One of the 441 messages from dump978 captured for that bird last night:
-08aa1add3897498910c247090360c5606e101f1f538f440bfea5c2a0004740000000;
Cheers!
LitterBug
Same bird is in several of my other 978 captures. He is the only one showing up on my UAT978 feed up > 18,000. The only time he is < 18,000 is when he is climbing out or descending in. Shouldn’t be to hard to set up a capture on both 978 and 1090 to see how the data compares.
Cheers!
Litterbug
[quote=“LitterBug”]
If you are running dump1090 you are not testing 978. dump1090 doesn’t decode data from the 978mhz band.
It is possible you picked up an aircraft that was broadcasting on 978 but only because it was retransmitted on 1090mhz
by a ground station.
Retransmits like this from ground stations are not a reliable way to receive on 1090 for ground stations using dump1090
because they are triggered by aircraft in proximity to each other AND require your ground station to be in range of the ground transmitter.
He’s running both dump1090 and dump978 so he is testing 978MHz actually.
The question is if, for cases where a message turns up on both 1090 and 978, whether both messages were transmitted by the aircraft or whether one was a rebroadcast by a ground station.
The two cases should be distinguishable by the message content assuming the ground station is setting up the messages correctly, but you need to look at the raw message contents - the map displays don’t show enough detail.
I would love a “how-to” set up a dual receiver system on my Pi. I have two dongles already, and I could probably stumble through it, but a bit of a bread crumb trail to follow would be good – especially the command line to insert into {some file} to start up the second dongle. Downloading from github and all I can do… and can probably stumble through compiling it, but again, if there are command line switches needed etc. having something to follow would be good.
Tell me, is the dump978 mutability feeding FLightaware ok? I understand that it successfully captures UAT traffic and displays them on the built-in web page (that’ll need to be configured as well, guessing a different port than 8080?)
And no, I have NOT yet downloaded dump978 nor read the readme or whatever all. I should probably do that, huh! How complete are those docs? Are those enough to satisfy my request above do ya think?
Thanks!
Don
dump978 is not much beyond a proof of concept at this stage. It will receive messages, decode them, with some setup it can display aircraft on a dump1090 style map. It does not currently feed to flightaware or anywhere else. Wouldn’t be a huge amount of work to package it all up and set up fatsv output for feeding to flightaware, but I would like someone else to pick that up - I have no UAT signals over here so that’s all low priority for me.
Obj, I could provide you access to a PI for 978 if you wanted it. I have only been playing with it. The volume is very low compared to 1090 so I have not been putting as much effort into it.
Regards,
LitterBug
I think I’m going to jump on the 978 bandwagon. I already have everything, but a good antenna.
I’m going to run on a separate Rpi/SDR. Ethernet crossover between the two Pi’s. The main/dump1090-mut Pi has network access through a USB WiFi connector. I believe I can have the main Pi act as a bridge for the second/978 Pi to have access to the network.
My question would be on the status of having Dump978 send data to the Pi with Dump1090-mut. Dump1090-mut then feeds to FA. I would like to have all the A/C data displayed on the main/Dump1090 web interface.
At the current state, is this feasible?
There is uat2esnt from the dump978 family of tools which will probably do this for you - it turns 978MHz UAT messages into 1090MHz DF18 ES/NT (“extended squitter, non-transponder”) messages that should be suitable for feeding to the raw (not Beast) port of dump1090 et al. Basically doing a very similar job to what a ground station would do when doing ADS-R forwarding of UAT to 1090MHz.
dump1090-mutability should understand DF18, but I have not tried feeding the data on to FA from that setup.
Also you’ll have to write a little glue script to set up the pipeline (approximately: rtl_sdr | dump978 | uat2esnt | nc)
Our FlightFeeder for Android app now supports UAT.
play.google.com/store/apps/deta … ightfeeder
To see UAT data, you’ll need to join our beta group though because we have not released it to the public yet.
Interesting… I’ll definitely have to check this out to see what traffic is in my area. I see lots of GA traffic in my area living close to the airport.
It can receive both 1090 and 978 (one at a time) or toggle between them. But, depending on your antenna setup, you may be isolated to one or the other. The 1090 capability is based on our PiAware software and the 978 capability is based on mutability’s work.
I installed it but I’m currently located inside a building and was only getting a few non-location based transponders plus I don’t get GPS in here. I’ll try again later when I have a better signal. Is there way to toggle between the 978 and 1090 or is it indicated?
By the time you get home tonight, we will have a new version available to the beta group, so join that if you haven’t. The public release version does not support UAT. When you get the beta version, you will be able to choose the scan mode - 1090 only, 978 only, or toggle between them, with the current mode indicated in the title bar of the main view.
When testing 978 and 1090 together on the same antenna, remember to remove any band filters that might isolate you to only one band.
I should also point out that because the app was originally patterned after PiAware (dump1090), it has a web server built into it so that you can view the map from a remote computer as long as it’s on the same network. The map will be a combined view of 1090 and 978 aircraft, although only the active band will animate.
I’ll give this a try. I have a COCO tuned for 978 and have been getting out 100-150 miles. So far it has been of very limited use. Only 47 unique ADS-B hits over a 4 day period. Alot more if you count the TIS-B feeds.
Cheers!
LitterBug
I’m guessing the new version is not out yet. I have no UAT mode yet. Will try again later tonight.
Cheers!
LitterBug
We published it about 2 hours ago, but it may be making its way through the interweb. Did you join the beta group?
You’ll know you have it if the version is 1.0.12, which you can check on the settings page.
The public version is 1.0.10. And there is a beta version 1.0.11, which has UAT support. So, if you don’t see either 1.0.11 or 1.0.12, then you must not have joined the beta group AND clicked the “Sign up for testing…” link at the top right of the page.