Ham radio operators often ask, "When are the bands going to be open, so I can make some DX contacts?" It's a constant question, and the answer depends on a lot of factors, most of which have to do with the sun's activity.
Most hams just guess, or spend fruitless hours listening for a possible opening. But there is a better way: propagation modeling with software, using solar data from NASA.
There are some very capable propagation modeling programs out there, but a lot of hams don't fool with them, because as one ham said, "I don't want to get a degree in solar astrophysics; I want to work DX." I'm an RF engineer, but still, I see his point.
Ham radio operator (and professional engineer) Stu Phillips, K6TU, created k6tu.net to take some of the voodoo out of HF propagation prediction. The site is "software as a service" that automates the whole process of prediction, and produces very nice signal strength maps like the one shown below, which identifies in color the areas of the world where your transmitter's signal is likely to be the strongest on a particular band on a particular day.
According to the website, there's even an inverse prediction, which "generates a set of predictions of what you can expect to HEAR. You select your station configuration as the RECEIVE configuration and then specify the configuration for the typical station you look to work including their output power level as the TRANSMIT configuration. Generally propagation is symmetric if all the path is in daylight. This prediction type is helpful for planning DXpeditions where the antennas and power levels are asymmetric."
Ol' Backwoods signed up for the 30-day test drive, and I have been mighty impressed so far. The predictions seem to line up with the stuff the ARRL puts out. I believe I will end up sending Stu $29.95 for a year of the service.
After you have customized your profile on the website with your transmitter power, antenna, location, etc., you can start a prediction program running. The program runs on a fast server, and will send you an email in a few minutes to an hour, with a link to your custom results page. Opening the PDF file on the page shows you predictions for the month on various HF bands, like the one below.
Pretty cool so far. I'll let y'all know how it goes.