What is generally the best time for long-distance 10-meter band propagation via the F region?
From dawn to shortly after sunset during periods of high sunspot activity✓الإجابة الصحيحة
From shortly after sunset to dawn during periods of high sunspot activity
From dawn to shortly after sunset during periods of low sunspot activity
From shortly after sunset to dawn during periods of low sunspot activity
الشرح
The F region is ionised by the sun, so its ionisation builds after dawn and only decays some time after sunset, and high sunspot activity raises the maximum usable frequency enough to include 10 metres. Both conditions must hold together, which rules out the night and low-sunspot options.