Re: FM Carrier Recovery for AOA Calculation

On 01/09/2023 16:39, Marcus Müller wrote:
> Ah, nice! yeah, then this would work – but! any oscillator has drift,
> so two local oscillators will not stay on the same phase for long; if
> your first couple measurements are correct, but suddenly your
> directions become very wrong, that's what I'd investigate.
>
> Cheers,
> Marcus
Looks like the BB60C supports an external 10MHz reference clock, which
would be utterly mandatory for anything requiring
  mutual phase-coherence, whether that's *sufficient* depends very very
much on the internal architecture of the BB60C.


>
> On 01.09.23 19:16, Michael Berman wrote:
>> The gr-aoa module has a calibration phase where you connect a source
>> with a splitter and roughly equally lengthened cables to the two
>> sources and it cross-correlates the two inputs to determine an
>> initial phase difference.  Then, while the script is still running,
>> you disconnect the calibration source and connect the antenna's,
>> again with roughly equally lengthened cables to run the MUSIC algorithm.
>>
>>
>> Thank you very much,
>>
>> Michael Berman
>>
>> On Fri, Sep 1, 2023 at 11:00 AM Marcus Müller
>> <marcus.mueller@ettus.com <mailto:marcus.mueller@ettus.com>> wrote:
>>
>>     If you don't know the relative phase of your two receiver chains,
>> how are you going to
>>     know the direction of a signal?
>>
>>     On 01.09.23 17:37, Michael Berman wrote:
>>>     Marcus,
>>>
>>>     Thanks for the reply!  I apologize, the GR package is gr-aoa,
>>> not gr-music, and can
>>>     be found here (https://github.com/MarcinWachowiak/gr-aoa
>>>     <https://github.com/MarcinWachowiak/gr-aoa>). The NOAA broadcast
>>> is a NBFM signal.     I am using 2 Signal Hound receivers
>>> (https://signalhound.com/products/bb60c/
>>>     <https://signalhound.com/products/bb60c/>) with 2 antennas
>>> spaced on a beam.  Do I
>>>     need to synchronize the 2 receivers with an external clock, or
>>> should they be fine
>>>     free running independently?
>>>
>>>
>>>     Thank you very much,
>>>
>>>     Michael Berman
>>>
>>>     On Fri, Sep 1, 2023 at 9:25 AM Marcus Müller <mmueller@gnuradio.org
>>>     <mailto:mmueller@gnuradio.org>> wrote:
>>>
>>>         Not familiar with the details of NOAA signalling, but isn't
>>> the carrier of an FM
>>>         signal
>>>         *the FM signal*?
>>>
>>>         For a DoA estimate, you'd correlate the different receive
>>> chains with each other
>>>         to get a
>>>         phase; so, as long as the signals do have some bandwidth
>>> that makes the problem
>>>         less
>>>         ambiguous, it'd work with any signal. I'm sadly not familiar
>>> with gr-music (and
>>>         can't find
>>>         it on cgran.org <http://cgran.org>), but MUSIC works as long
>>> as the signals at
>>>         the different receive antennas
>>>         are correlated and noise is not. You do not have to
>>> preprocess your FM signal!
>>>
>>>         Best,
>>>         Marcus
>>>
>>>         On 01.09.23 17:09, Michael Berman wrote:
>>>         > Does anybody know if there is a way to recover a carrier
>>> of an FM signal to
>>>         use for an
>>>         > Angle of Arrival calculation?  I am using GNURadio and
>>> gr-music and I am
>>>         trying to use the
>>>         > NOAA Weather Radio signals.
>>>         >
>>>         > Thank you very much,
>>>         >
>>>         > Michael Berman
>>>
>