Assertion: radio wave's frequency | /r/CapableOf | vary in the course of the day
Facets:
value: from year
type: TEMPORAL
value: between approximately 5 and 10 mhz
type: TEMPORAL
Source sentences:
text: The critical frequency of the F 2 layer (the principal maximum in Figure 12) varies in the course of the day and from year to year between approximately 5 and 10 MHz.