52Re: [dxatlas] Newbie questions (tons of them)
- Apr 28, 2004Hello,
> 1) What do the light and dark areas mean on the map? Does dark meanIf you are talking about the HamCap SNR map, then brighter areas correspond
> 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?
to higher SNR.
> 2) What does SNR mean? What is SNR? Why do I need to know this?SNR is Signal-to-Noise Ratio.
> How does it affect QSO's?
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 MUFThe MUF and other parameters displayed on the status bar in HamCap are for
> 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 path that starts at your home QTH and ends at the point under the
> 4) The MUF is the maximum (ie. highest) frequency that, based on theUsually the best frequency is about 80% below MUF, but there are exceptions.
> SSN, etc, is best to reach the station?
See my answer to question 2.
> 5) The critical frequency is the highest frequency you can use beforeYes
> the radio waves start going through the ionosphere?
> 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 toNo. You would select the frequency with highest SNR.
> work, then find out the MUF and stay below that and the Crit Freq?
> 8) When I have the 3 apps open at once, there is a little yellow sun-This is the sunrise and sunset time for the point under the mouse cursor.
> like icon down on the bottom of DXAtlas that displays a number like
> 8:33-21:15. What does this mean?
73 Alex VE3NEA
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