Comparison of different methods for calculating the absorption of high-frequency radio waves

For different paths and using a global model of the ionosphere, the absorption of radio waves at different frequencies greater than 10 MHz is calculated by the integral, LH, NBS, CCIR, and Kazantsev methods. A comparison of the calculated absorption values shows that the differences between the five methods are smallest for midlatitudes. However, the difference between the CCIR method and Kazantsev method is substantial (up to 50 percent) even at midlatitudes.