Advantages and Disadvantages of Ground wave,Sky wave

This page covers advantages and disadvantages of Ground wave and Sky wave. It mentions Ground wave advantages, Ground wave disadvantages,Sky wave advantages and Sky wave disadvantages.

What is Ground wave?

The ground wave follows contour of earth and hence it can propagate considerable distances. It exists below 2 MHz frequency range.
Example: AM Radio

Ground wave propagation

The figure-1 depicts ground wave propagation.

Advantages of Ground wave

Following are the benefits or advantages of Ground wave:
➨As it uses lower frequencies, interference occurs due to atmospheric noise only. Moreover absorption of EM waves at lower frequencies are less. Hence it can cover longer distances. However the pathloss increases as distance from transmitter increases. Hence distance between Tx and Rx should be optimal.
➨They are vertically polarized in order to prevent short circuit of electric field (E) component.

Disadvantages of Ground wave

Following are the disadvantages of Ground wave:
➨If the polarization of ground wave is affected, E field components are short circuited with the ground.
➨The distance between two antennas ( transmit (Tx) and receive (Rx) ) should not be too large, otherwise received signal strength gets reduced too much due to ground and atmospheric absorptions. Hence communication can not be established between two stations. Often this requires use of repeaters in between Tx and Rx. This increases overall cost of the system.

What is Sky wave?

The signals are reflected from ionized layer of the atmosphere known as Ionosphere. Here signals can travel number of hops, back and forth.
Example: SW Radio

Sky wave propagation

The figure-2 depicts sky wave propagation. Sky waves exist from 2 MHz to 30 MHz frequencies.

Advantages of Sky wave

Following are the benefits or advantages of Sky wave:
➨As it utilizes reflective property of ionosphere available above earth at higher frequencies, it is most simple mode of propagation and provides continuous support in communications.

Disadvantages of Sky wave

Following are the disadvantages of Sky wave:
➨Ionoshere is present near or far during night time and day time respectively. Due to this, Sky waves can travel longer or smaller distances.
➨Transmitter signal travels multiple hops before reaching the receiver. This reduces signal strength considerably if distances are larger between transmitter and receiver antennas.

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