Learning Objective 090.06.01.01.06: List the factors which reduce the effective range and quality of VHF radio transmissions.

Attenuation is the term given to the loss of signal strength in a radio wave as it travels outward from the transmitter. It limits the range of radio signals.

We can say that attenuation is affected by a number of factors including:

• The materials a signal travels through => the higher the density of the material – the higher the attenuation.
• Frequency and wavelength => higher frequencies and lower wavelengths suffer from higher attenuation – because they have a higher number of peaks which causes a higher number of energy fluctuations and energy loss over distance, being more prone to attenuation.

SUMMARY:
Attenuation increases as:

• air density increases
• wavelength decreases
• frequency increases
• air temperature decreases

Note: with regards to the air, provided that pressure remains constant – the lower the temperature, the higher the density => attenuation increases with temperature decrease.