Getting started

To get started with VOAProp:

  • Start the program.
  • If the "Locate / Install VOACAP" dialog appears:
    - If VOACAP is not already installed, click "Open VOACAP download site", download and install VOACAP;
    - Click "Locate VOACAP installation folder" and select the folder in which VOACAP is installed;
    - The dialog should then close. If you do not carry out this step correctly then VOAProp will not display any propagation information on the map.
  • Right-click the map. Most of the configuration options are on this right-click menu.
  • Select "Set home location" and enter the details for your location. To set the location using your QTH locator, enter the locator and hit Tab.
  • Optionally, select "Short wave bands" instead of "Amateur bands".
  • Ensure that at least one of "Show signal strengths" or "Show workable call areas" is selected. Signal strengths are a relative measure, shown by contour lines indicating S1, S5 and S9. Call areas are shown by their prefix letters, with a bright font illustrating the strongest signals.
  • Click the "Solar data" button, then click "Update" to download the latest solar-terrestrial data from WWV. The smoothed sunspot data file and the IARU beacon activity file will also be periodically updated.
  • Check the "Auto update" box if you want these files to be updated automatically in future.
  • Select the band or map of interest.
  • Adjust the sensitivity slider between "High" and "Low" so that the propagation indicated by the map best matches the capabilities of your station. (As a rough guide, you can take High as 4KW+tower mounted beam, Medium as 100W+dipole, Low as 1W+low dipole. On the short wave bands, use 100W to 4MW.)

The Date and Time controls of VOAProp only allow the month, year and hour to be set. This is because VOACAP only produces average predictions for the month. Its input parameters do not have a field for the date, or the exact time to the nearest minute. If you would like VOAProp to display the UTC time, it can do this in the title bar of the window. Just select "Show UTC time in title bar" on the menu.

If you check "Auto update" on the main window, the Date and Time controls will keep in step with the system clock, and the propagation display will be refreshed every hour. To investigate past or future propagation, uncheck this box. VOAProp will use values from its database of smoothed sunspot numbers, going back to the year 1900. Note that the WWV solar data values (solar flux, A index and K index) are hidden when "Auto update" is unchecked, because they are only valid for the current time and date.

Path predictions

You can get an idea of the best time to communicate with a particular location by clicking on that location with the mouse (or right-clicking the map and choosing "Set DX location".) A yellow line will be drawn showing the path (check the "Long Path" box to investigate long path propagation) and the "S meter" display in the status line will give an indication of the current signal strength from that location. (When an IARU beacon is displayed, the "S meter" shows the signal strength of the currently transmitting beacon.)

Click "Show chart" to see a chart of propagation conditions and expected signal strengths over that path throughout the day. You can print the chart by clicking the printer icon at the lower left of the chart window. Check the "Preview" box to start with a print preview. For more control over the printed output, click the "Copy" icon to copy the chart to the clipboard. You can then paste it into Microsoft Word or a similar application, resize it, or add multiple charts to one document.

To see what propagation would be like from another location without permanently changing your stored home location, right-click the map and choose "Set alternative location." Use "Set home location" to change it back again.


Propagation prediction is not an exact science. In any case, the propagation shown on the map is only the expected propagation under average conditions for the time of day during the selected month, based on the predicted Smoothed Sunspot Number for that month. The VOACAP model knows nothing about the actual state of the ionosphere at this particular moment in time. Therefore observed propagation will inevitably differ to some extent from that shown.

To help give a better idea of what actual conditions should be like, VOAProp obtains the latest solar data from WWV and uses them to display a qualitative indicator of band conditions. (Note that this information is only shown when "Auto update" is checked, because the WWV data is only valid for the current time and date.)

The indicator of conditions may be assessed as follows:

  • Very good: Propagation may be much better than shown.
  • Good: Propagation may be a little better than shown.
  • Average: Propagation will be approximately as shown.
  • Fair: Propagation will be a little worse than shown.
  • Poor: Propagation could be a lot worse than shown.
  • Disturbed: It is possible that there could be little or no propagation at all.

Next page: Beacon monitoring