Another failure of decoding UAT

Pete Zaitcev zaitcev at
Wed Jan 22 16:54:52 UTC 2014

I know someone who's reveiving FIS-B with a GDL 39, although his
home base is about 100 km north-east. I'm somewhat confident that
I should have the coverage. One problem is, from what I heard,
the ground stations will not broadcast anything until a UAT-equipped
aircraft checks in.

Regardless, I was hoping that Nick or other experts chime in on
the code itself. Honestly I have no clue what I'm doing here.
I imagine that if signal is present, then vector pointed by Q+jI 
rotates at ~300 revolutions per second. Therefore, I calculate
the phase angle difference between two samples taken at twice
the UAT bit rate and see if it's anywhere reasonable. It may
be a bogus technique for any number of reasons.

-- Pete

On Wed, 22 Jan 2014 08:25:57 -0800
David Jacobowitz <david.jacobowitz at> wrote:

> This may be dumb because I haven't looked into it, but is it reasonable to
> expect to receive a signal?
> Are you in the US? There really aren't that many UAT equipped aircraft yet.
> The FAA is rebroadcasting ADSB ES responses on UAT as well as providing
> weather and other data, but that is all coming from ground stations. If you
> need line of sight and you're on the ground yourself you may be out of luck.
> - Dave J

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