The only change that I spotted in this section is a slight change to the answer of question G3B04.
The two most important parameters for predicting the propagation between two locations are the MUF and LUF. MUF stands for the Maximum Usable Frequency for communications between two points. (G3B08) LUF stands for the Lowest Usable Frequency for communications between two points. (G3B07)
When they are sent into the ionosphere, radio waves with frequencies below the Maximum Usable Frequency (MUF) and above the Lowest Usable Frequency (LUF) are bent back to the Earth. (G3B05) When they are sent into the ionosphere, radio waves with frequencies below the Lowest Usable Frequency (LUF) are completely absorbed by the ionosphere. (G3B06) No HF radio frequency will support ordinary skywave communications over the path when the Lowest Usable Frequency (LUF) exceeds the Maximum Usable Frequency (MUF). (G3B11)
All of these choices are correct when talking about factors that affect the Maximum Usable Frequency (MUF) (G3B12):
- Path distance and location
- Time of day and season
- Solar radiation and ionospheric disturbances
When selecting a frequency for lowest attenuation when transmitting on HF, select a frequency just below the MUF. (G3B03) A reliable way to determine if the Maximum Usable Frequency (MUF) is high enough to support skip propagation between your station and a distant location on frequencies between 14 and 30 MHz is to listen for signals from an international beacon in the frequency range you plan to use. (G3B04)
While signals most often take the shortest path from point to point, sometimes the best path for radio propagation is in the opposite direction, also called the “long path.” A well-defined echo might be heard if a sky-wave signal arrives at your receiver by both short path and long path propagation. (G3B01)
The 6m band is a favorite of many amateur radio operators, even though it infrequently supports long-distance, skywave propagation. A good indicator of the possibility of sky-wave propagation on the 6 meter band is that there is short skip sky-wave propagation on the 10 meter band. (G3B02)