What is the effect on skip distance of HF-transmission when frequency and position of the reflecting ionospheric layer increase?

The skip distance in HF (High Frequency) transmission is influenced significantly by the frequency of the radio wave and the altitude of the reflecting ionospheric layer. When both the frequency and the altitude of the reflecting layer increase, the skip distance also increases.

Higher frequencies tend to reflect from the ionosphere at higher altitudes more effectively, allowing for a greater distance between the transmitter and the point where the signal returns to Earth. This extension of distance occurs because higher frequency waves generally have a steeper incidence angle upon reflection, which allows them to skip further before returning to Earth.

Additionally, when the ionospheric layer is located at a higher position, it can also enable the signal to cover a larger geographical area before it skips back to the ground. The combination of a higher frequency and the higher position of the reflecting ionospheric layer leads to an extended skip distance, making communication possible over larger distances.

In contrast, lower frequencies and/or lower ionospheric layers would not support the same effective propagation characteristics, leading to shorter skip distances, as signals would not travel as far before returning to Earth. This reinforces why the choice indicates that an increase in both frequency and the altitude of the reflecting layer results in a greater skip distance.