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TIS-B position messages

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  • TIS-B position messages

    I'm using a DVB dongle, 10-element CoCo with inline satellite amp, dump1090 feeds Virtual Radar Server and ADSBScope. I noticed ADSBScope decodes and plots TIS-B position messages (VRS does not) and I can feed those back to VRS via merged feed for basestation logging purposes.

    What's strange is, I'm in Reno, surrounded by mountains and should not be able to receive traffic low near San Francisco, yet there they are, many of them each day usually between 2,000 and 10,000 feet, all are Mode-S only so the positions are coming from TIS-B, They drop off the screen just outside the Bay Area (and if they head up this way I picked them back up a few minutes later with no position messages). Here is a screen shot from VRS Google map:

    Ducting? Or maybe a TIS-B repeater somewhere nearby?
    tis-b.jpg

  • #2
    TIS-B is a repeater by definition. It transmits radar tracks received by real radars in an ADS-B like format. The tracks are only transmitted on TIS-B if the aircraft do not transmit ADS-B on 090 MHz by themselves. So a Mode-S only aircraft will appear on TIS-B, while a 1090ES ADS-B aircraft will not.

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