I would like to ask your opinion regarding this matter:
Based on the relation of frequency and wavelengths, the higher the frequency, the shorter the wavelengths and therefore the distance of travel is lower. Assuming two frequencies from the ISM band: 2.45GHz and 5.8GHz.With the same amplitude and antenna gain, the frequency of 2.45GHz will travel further than the 5.8GHz based on their wavelengths.
However, in this link under the subtopic of frequency, it is mentioned that
"In general, the higher the frequency, the greater is the range. RF radiation has more energy at the higher frequencies."
In this case, the range does depend upon the both the transmitter power and operating frequencies. Does it suggest that higher frequencies have naturally higher amplitudes which may cause them to travel further or higher frequencies needs to be supplied with sufficient transmitting power in order to improve its distance compared to lower frequencies ?