What is the SWL best time of day for listening to your radio? There is no complete answer, but here are some clues.
I do much of my shortwave broadcast listening on the 31 and 25 meter bands covering 9 and 11 MHz, respectively. Being in the middle of the HF spectrum, you will find these bands are almost always open to somewhere. You can also get really strong signals with a modest antenna, even a portable radio.
Recently, I have been writing about propagation. In particular, I have described how the lower D ionosphere layer can absorb or attenuate signals during daytime, everywhere. So, one strategy you can use to find SWL best time of day is to make sure the path from your house to the target is covered by darkness.
The D layer does not refract radio signals at HF, but it sure does absorb them. Being a weaker layer, you will find that ions and electrons recombine rapidly after sunset. Then, signals have an unimpeded path to bounce of the F layer a great distance from medium waves up.
My home is in western Canada. Above left, you can see my path to Greece in the evening. The D layer has gone away, and absorption is reduced as shown at the blue level in the graph. Meanwhile, on 31 meters, the MUF remains high enough to hear Voice of Greece. (At least, when they were still on the air at 9420 kHz.)
Over on the right, you can see my path to Singapore in the early morning at my house. Still to early for the D layer to form, so again, absorption is low. But my maximum useful frequency MUF is still high enough for good Asian signals on 25 meters.
SWL Best Time of Day depends on where you live
Of course, everything depends on location. My SWL habits are mostly driven by time of day, rather than solar cycle. When listening on the mid-HF frequencies, these frequencies are almost always open unless the ionosphere gets disturbed.
The above graphs and maps are produced by my Ergo Radio Software, which links maps, propagation, radios and databases. Although nearing end of life, I find this software very useful for understanding what’s going on.