For the last several weeks I have been working with the developer of the Skyguard ADS-B units. I was seeing traffic reports of some 1090ES traffic indicating altitudes as high as 101,000' as well as reporting altitudes of 800' and 2200', which would be believable in most places, but since ground level here is mostly around 6500' or higher, I was having a hard time believing the display. We managed to shake 3 different bugs out of the firmware while trying to diagnose the problems, which were fixed by a new firmware patch installed to my unit 3 weeks ago. So, if you are using a Skyguard unit, I would recommend that you arrange to return it for a firmware upgrade to fix several ADS-B altitude reporting issues.
To be more specific, Mode-C traffic reported by the ADS-B towers was correct. UAT traffic was being displayed correctly. 1090-ES traffic with a blind encoder was being displayed correctly. But 1090ES traffic using a gray code encoder was being mishandled and the altitudes were being reported incorrectly. With the incorrect altitudes being displayed, if you have any altitude filters turned on, the traffic with the mishandled altitudes will not be displayed even though it may be at your altitude. There were also two other issued more minor in nature that we shook out as well, so those issues will also be fixed if you return your unit for a firmware upgrade. Additionally, I also found the old Terra transponders may be incompatible with ADS-B receivers. I had my transponder bench checked, and it meets the TSO specs for the transponder. However, unlike most transponders, the Terra transponder has a oscillator that runs at 1090 MHz that (at least in mine) is apparently noisy enough that it effectively blocks most of the 1090ES traffic reception. I tried this with 3 separate ADS-B receivers, all of which were also tested and worked fine with other transponders. -Jeff Scott Los Alamos, NM _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
