Ham Radio General Class Practice Test

Which of the following might indicate that signals on the HF bands are being received via scatter propagation?

1. The communication is during a sunspot maximum

2. The communication is during a sudden ionospheric disturbance

3. The signal is heard on a frequency below the Maximum Usable Frequency

4. The signal is heard on a frequency above the Maximum Usable Frequency

The correct answer is: The signal is heard on a frequency above the Maximum Usable Frequency

Receiving signals on a frequency above the Maximum Usable Frequency (MUF) likely indicates that the signals are being received via scatter propagation. This is because the MUF is the highest frequency at which a radio wave can be transmitted between two points via the ionosphere under normal conditions. When signals are heard above this frequency, it typically suggests that the propagation conditions are atypical, often resulting from phenomena such as scatter from atmospheric irregularities or other non-standard ionospheric conditions. In scatter propagation scenarios, such as when signals are reflected off meteor trails or other irregularities in the atmosphere, it is possible for signals to reach a receiver even at frequencies that exceed the predetermined MUF. The occurrence of this kind of propagation is not limited to any specific solar activity or ionospheric disturbances. The presence of these signals indicates that transmission paths may be reflecting or refracting in ways typical signals would not under more stable conditions. The other options focus on different phenomena not directly indicative of scatter propagation. For instance, communications during a sunspot maximum may enhance HF band propagation generally but do not specifically relate to scatter. Sudden ionospheric disturbances can cause unpredictable propagation effects but do not specifically confirm scatter. Lastly, signals heard below the MUF typically indicate standard propagation