Mention three different modes of propagation used in communications system. Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves?

Mention three different modes of propagation used in communication system. Explain with the help of a diagram how long distance communication can be achieved by ionospheric reflection of radio waves.

Explain basic elements of communication system with the help of block diagram.

Draw and explain with the help of block diagram, elementa of communication system.

Distinguish between Sky wave and Space wave modes of propagation in a communication system.

Distinguish between Sky wave and Space wave modes of propagation in a communication system.

Distinguish between Sky wave and Space wave modes of propagation in a communication system.

Which mode of propagation is used by short wave broadcast services having frequency range from a few MHz upto 30 MHz ? Explain diagrammatically how long distance communication can be achieved by this mode . Why is there an upper limit to frequency of waves used in this mode ?