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#2682 NDB frequency should accept half frequencies

2020.3
New
nobody
Low
2023-10-24
2021-12-24
legoboyvdlp
No

NDBs can have half frequencies - for instance EME 353.5 kHz near East Midlands airport. Currently the adf instrument can only accept full frequencies as the property is an int.

Discussion

  • James Turner

    James Turner - 2022-01-06

    Maybe need a discussion on the list about handlign this, eg do we need to add a config property to the NDB cxx instrument, eg config/accept-half-freq= true ? And in this case the frequency type will be double, not int?

     
  • legoboyvdlp

    legoboyvdlp - 2022-01-06

    Agree. Yes it would be double. Actually - X-Plane's data format can only do integers, so maybe this is a can't fix / won't fix, since it would be difficult to do this without X-Plane changing their specification for nav.dat?

     
  • James Turner

    James Turner - 2022-01-06

    Welll .... is there a way we can aks them? At this point we have a few edits, I'm not adverse to adding support for fractions on our side, it's niot like we need our nav.dat to remain compatible.

     
  • legoboyvdlp

    legoboyvdlp - 2022-01-06

    Apparently the bandwidth of NDB's is big enough that it's fine to tune the frequencies 500 Hz lower, and you'll still pick up the NDB. Many commercial NDB instruments don't support the decimal point. Although Airbus does support it!

    it's niot like we need our nav.dat to remain compatible.

    As long as backwards compatibility is maintained? Without having our own data source

     
  • James Turner

    James Turner - 2022-01-07

    What I mean is, we could make our parser support a decimal in that column, and just edit our nav.dat, and we'd be fine, as far as I can see. Do you agree?

    (And, we're already making drive-by edits to these files in particular cases, since we're not doing any /other/ updates...)

     
  • legoboyvdlp

    legoboyvdlp - 2022-01-07

    OK; that's fair enough -- the only thing to be wary of, then, is whether custom ADF instruments will still work.

     
  • James Turner

    James Turner - 2022-01-07

    Can you point me at any examples? I'm guessing most will not care that the property is a double, unless they do something very specific.

     
  • legoboyvdlp

    legoboyvdlp - 2022-01-07

    c172p\Models\Interior\Panel\Instruments\kr87-adf\
    Aircraft\Instruments-3d\kr87-adf

    At least these 2.

    The A320 has its own code of course as well. but it supports decimals. They just can't be tuned yet.

     
  • Mariusz Matuszek

    Researching NDB's I came across this discussion..
    Would an acceptable solution be to keep the original interface intact (i.e. the frequency property remains an int) and add second property (like int frequency_fraction) to the instrument?

    This additional property would default to zero, so all existing ADF instruments would simply continue to work as if nothing had changed.

     
  • James Turner

    James Turner - 2023-10-21

    That's possible but I'm not sure it really helps anyone: a config property is opt-in and if people set it, they can deal with a non-integer frequency, and other systems (generic radio dialogs, etc) can also detect this case.

    If we add a second property for the fraction, we have to base UI policy, etc on whether it's zero or not, but that is not very nice: what we want to know is whether the ADF tune can or can't handle fractional frequencies, and a config property is the right way to do that.

    All 'in my opinion' of course.

    See also the discussion about, in our current navaid DB, we cannot actually model fractional NDB frequencies, I think.

     
  • Mariusz Matuszek

    You are right.
    I think I missed the 'opt-in' idea. Sorry for making noise in this thread.

     

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