LodeRunner sends the following guide to using the online propagation predictor tool. As most of you with HF experience likely know, the solar conditions have been quite a challenge as of late and will likely be so for a while to come. That said, regional and long haul HF communications are definitely possible even at low power levels provided one has a basic grasp of the way propagation works, how to wring the most efficiency out of their antenna arrays, and the best operating techniques for your intended purpose. One easy way to plan your regional communications is by using the HF Propagation Prediction tool.
On-Line Tools for HF Propagation Prediction
HF communications, and particularly NVIS communications on 160/80/40 Meters, are highly dependent upon conditions in the Earth’s ionosphere, which can change rapidly as a result of solar influences. Being able to predict the “Space Weather” is beyond the capability of most amateur radio operators. Thankfully, there are a number of on-line resources which reduce this to a few minutes work for you. Below I give a quick primmer on using one of the easiest on-line tools for this purpose.
Courtesy of the Australian government, you can run a fast and free Hourly Area Prediction (HAP) for your location and desired coverage area. The tool is located at:
You’ll need to select some starting parameters, as follows –
The location of your Base: Simple Click/drag on the map, or enter LAT/LON on the [BASE] tab of the page. The location of you ‘Base’ will be indicated on the map by a small triangle icon.
The Area you want to see the prediction for: Go to the [AREA] tab and enter a center LAT/LON and area size in degrees. Once you have entered these you may go back to the [MAP] tab and drag the selected (pink box) area if desired. The area you can run a prediction set for is limited – 20deg X 30deg works, and provides appropriate resolution for NVIS communications
Frequencies: go to the [FREQS] tab and click the [AMATEUR] button
Date and Conditions: go to the [DATE + T] tab and select the date on the calendar. If you’re running a prediction for tomorrow, then simply click on the [Northern Hemisphere] button to load the current atmospheric conditions for North America. If running a prediction for more than a day into the future, then a little ‘guessing’ is in order – The prediction tool uses what is called a “T-Index” instead of the more familiar SSN# (Smoothed Sunspot Number) so it’s not too difficult – setting the T-Index to 0 simply gives you their predicted value for that day. Positive numbers represent ionospheric enhancement above their predicted conditions, and negative numbers represent depressed ionospheric conditions (compared to their prediction).
Once you have made the selections above, then click the large blue [PREDICT] button in the upper right. Once you have done so, five new tabs will appear.
The [RESULTS] tab is in text format, and simply summarizes your input.
The [0-5UT], [6-11UT], [12-17UT], and [18-23UT] tabs are the charts for those hours in UTC (ZULU time), and look like this –
Reading these area predictions is simple. Simply look at the point on the map where the mobile/remote station is located, and the color of the map overlay at that location indicates the HF band with the best (predicted) conditions for making contact with that location from you Base location.
In this example, the Base is located in northeastern North Carolina. As you can see, the current NVIS conditions favor 80 Meters for communications during daylight hours, and 160M from 90 minutes after sunset [after 1900h/EST or 0000h/UTC] throughout the night, until about 30 minutes after sunrise 0800h/EST 1300h/UTC].
As we proceed towards the Solar Minimum, predicted to occur in 2019 or 2020, propagation will favor 160 Meters for NVIS communications to an increasing degree – near the Minimum, 160 Meters may be THE ONLY effective band for NVIS, 24 hour a day, for a year or more. For this reason I’ve prepared a forthcoming article on using a simple Inverted-L antenna for 160M and 80M NVIS communications.