Name the two radio waves that propagate near to the surface of the earth.

How are ground waves polarized?

What is the frequency range of signal that propagate best over the surface of the earth?

Identify the radio waves which are refracted by the ionosphere.

Mention the range of frequency signals that porpagate best through ionosphere.

-------- is the upper portion of the atmosphere, which absorbs large quantities of radiant energy from the sun and becomes heated and ionised.

Which layer of the ionosphere has the greatest effect on a radio signal?

Which is the type of radio wave that propagates only over line-of-sight distance?

What is fading?

------ is the minimum distance measured between transmitting antenna and the first receiving antenna measured along the surface of the earth after propagation through the ionosphere.

------- is the region around the receiving antenna, within the skip distance, where neither the ground wave nor sky wave is present.

------- it is the maximum angle of incidence of a radio wave under ionospheric propagation that gets returned to the earth.

------- is the highest frequency of a beamed radio wave that will be returned to the earth.

is any unwanted electrical energy which interferes with the required signal.

1. ------ is the ratio of signal power to noise power.

2, -------- is the ratio of signal to noise ratio at the input to the signal to noise ratio at the output of the system.

----- is the noise ratio expressed in decibel.

10⁴ to 10¹⁴ Hz.

IS

is the maximum distance between transmitting antenna to first receiving antenna measured along the surface of the earth after propagation through the ionosphere.

this block diagram is

Mention the layers of ionosphere.

for Long distance communication

for Navigation services

for Radio broadcasting. Police walkie-talkie.

for Telephone,aviation.------

for Radar, TV, Fm broadcasting.-------

Satellite communication Radar.-----------

Special purpose communication.--------

------ is at a height of 150 km and extends upto 400 km. It remains during both day and night . time. During day time, it splits into two layers Fj and F₂ and combines to form a single F layer during night time.

___ layer of ionosphere is at a height of 70 km which has a thickness of 10 km. It disappears at night and reflects VLF and LF waves

___ layer of ionosphere is at a height of 100 km and has a thickness of 25 km. It disappears at night and helps MF and HF wave propagation.

___ layer or ___ layer is at a height of 200 km with a thickness of 20 km. It reflects HF waves.

___ layer or ___ layer is at a height of 300 km and has a thickness of 20 km. It is useful in HF wave propagation.