i) LOS: Line Of Sight communication.
ii) In this communication the space waves travel directly from transmitting antenna to receiving antenna.
iii) Frequency for LOS must be more than 40 MHz.

(i) Because the transmission of signal directly from the transmitting antenna to receiving antenna called a line of sight communication.
(ii) The waves traveling directly from the transmitting antenna to the receiving antenna get blocked due to curvature of the earth.
(iii) It limits both the maximum line of sight distance between the two antennas arid also the maximum distance up to which transmission can be received.

i) Weather Satellites : They are used to monitor the weather and climate of Earth. By measuring cloud mass, these satellites enable us to predict rain and dangerous storms like hurricanes, cyclones, etc.
ii) Navigation satellites : These are employed to determine the geographic location of ships, aircraft or any other object.
iii) Communication satellites: Thev are used to transmit television, radio, internet signals etc. Multiple satellites are used for long distance communication.

i) Large decrease in noise. This leads to an increase in signal-noise ratio.
ii) The operating range is quite large.
iii) The transmission efficiency is very high as all the transmitted power is useful.
iv) FM bandwidth covers the entire frequency range which humans can hear. Due to this, FM radio has better quality compared to AM radio.

Advantages of AM :
(i) Easy transmission and reception
(ii) Lesser bandwidth requirements
(iii) Low cost
Limitations of AM :
i) Noise level is high
i) Low efficiency
ii) Small operating range