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Re: [dxatlas] Newbie questions (tons of them)

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  • Alex, VE3NEA
    Hello, ... If you are talking about the HamCap SNR map, then brighter areas correspond to higher SNR. ... SNR is Signal-to-Noise Ratio. Three factors affect
    Message 1 of 2 , Apr 28, 2004
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      Hello,


      > 1) What do the light and dark areas mean on the map? Does dark mean
      > that that area on the map is a dead zone? Or does it mean ionization
      > is highest there and thus the best chance of contacting a station?

      If you are talking about the HamCap SNR map, then brighter areas correspond
      to higher SNR.



      > 2) What does SNR mean? What is SNR? Why do I need to know this?
      > How does it affect QSO's?

      SNR is Signal-to-Noise Ratio.

      Three factors affect the availability of the path: 1) MUF. If the MUF is
      below the operating frequency, the path is closed, no matter how much power
      you put in the antenna; 2) path losses. Signal absorption along the path can
      result in a closed path even if the MUF is high enough; 3) noise level. Even
      if the MUF is right and the signal is strong, the path still may be closed
      if the noise in the recipient's area is stronger than your strong signal.
      You can estimate these 3 parameters separately to see if the path is open or
      not, but it is more convenient to just check the predicted SNR, as this
      parameter takes into account all three factors. If the SNR is 3 dB or
      higher, your chances are good.



      > 3) When I move my cursor around the map in DXAtlas, I see the MUF
      > change in HamCAP. Is that the MUF for me trying to reach that
      > location (the location where my cursor is)? Or would I put the
      > cursor over my QTH and go off what it is telling me the MUF is?

      The MUF and other parameters displayed on the status bar in HamCap are for
      the path that starts at your home QTH and ends at the point under the
      cursor.



      > 4) The MUF is the maximum (ie. highest) frequency that, based on the
      > SSN, etc, is best to reach the station?

      Usually the best frequency is about 80% below MUF, but there are exceptions.
      See my answer to question 2.



      > 5) The critical frequency is the highest frequency you can use before
      > the radio waves start going through the ionosphere?

      Yes



      > 6) How do critical frequency and MUF differ then?

      Critical frequency is just the MUF of a vertical path.




      > 7) From what I understand, you would find a place you would like to
      > work, then find out the MUF and stay below that and the Crit Freq?

      No. You would select the frequency with highest SNR.



      > 8) When I have the 3 apps open at once, there is a little yellow sun-
      > like icon down on the bottom of DXAtlas that displays a number like
      > 8:33-21:15. What does this mean?

      This is the sunrise and sunset time for the point under the mouse cursor.



      73 Alex VE3NEA
    • digitaleli
      Man you are so helpful! Thanks soooo much for the quick reply and answers to my questions! Not only are you a GREAT programmer, but your very quick to answer
      Message 2 of 2 , Apr 28, 2004
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        Man you are so helpful! Thanks soooo much for the quick reply and
        answers to my questions! Not only are you a GREAT programmer, but
        your very quick to answer any posts or patch any issues. I am glad I
        purchased DX Atlas and am eagerly looking forward to any other
        software you will release. Cheers!

        73,
        KC0RDG

        --- In dxatlas_group@yahoogroups.com, "Alex, VE3NEA" <alshovk@d...>
        wrote:
        > Hello,
        >
        >
        > > 1) What do the light and dark areas mean on the map? Does dark
        mean
        > > that that area on the map is a dead zone? Or does it mean
        ionization
        > > is highest there and thus the best chance of contacting a station?
        >
        > If you are talking about the HamCap SNR map, then brighter areas
        correspond
        > to higher SNR.
        >
        >
        >
        > > 2) What does SNR mean? What is SNR? Why do I need to know this?
        > > How does it affect QSO's?
        >
        > SNR is Signal-to-Noise Ratio.
        >
        > Three factors affect the availability of the path: 1) MUF. If the
        MUF is
        > below the operating frequency, the path is closed, no matter how
        much power
        > you put in the antenna; 2) path losses. Signal absorption along the
        path can
        > result in a closed path even if the MUF is high enough; 3) noise
        level. Even
        > if the MUF is right and the signal is strong, the path still may be
        closed
        > if the noise in the recipient's area is stronger than your strong
        signal.
        > You can estimate these 3 parameters separately to see if the path
        is open or
        > not, but it is more convenient to just check the predicted SNR, as
        this
        > parameter takes into account all three factors. If the SNR is 3 dB
        or
        > higher, your chances are good.
        >
        >
        >
        > > 3) When I move my cursor around the map in DXAtlas, I see the MUF
        > > change in HamCAP. Is that the MUF for me trying to reach that
        > > location (the location where my cursor is)? Or would I put the
        > > cursor over my QTH and go off what it is telling me the MUF is?
        >
        > The MUF and other parameters displayed on the status bar in HamCap
        are for
        > the path that starts at your home QTH and ends at the point under
        the
        > cursor.
        >
        >
        >
        > > 4) The MUF is the maximum (ie. highest) frequency that, based on
        the
        > > SSN, etc, is best to reach the station?
        >
        > Usually the best frequency is about 80% below MUF, but there are
        exceptions.
        > See my answer to question 2.
        >
        >
        >
        > > 5) The critical frequency is the highest frequency you can use
        before
        > > the radio waves start going through the ionosphere?
        >
        > Yes
        >
        >
        >
        > > 6) How do critical frequency and MUF differ then?
        >
        > Critical frequency is just the MUF of a vertical path.
        >
        >
        >
        >
        > > 7) From what I understand, you would find a place you would like
        to
        > > work, then find out the MUF and stay below that and the Crit Freq?
        >
        > No. You would select the frequency with highest SNR.
        >
        >
        >
        > > 8) When I have the 3 apps open at once, there is a little yellow
        sun-
        > > like icon down on the bottom of DXAtlas that displays a number
        like
        > > 8:33-21:15. What does this mean?
        >
        > This is the sunrise and sunset time for the point under the mouse
        cursor.
        >
        >
        >
        > 73 Alex VE3NEA
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