2. There are two basic type of electronic communication
COMMUNICATION
Simplex
Duplex
One way communication
information travels only one direction
Two way communication
information travel in two direction
Ex : Radio and Television
Ex : telephone
3.
4.
5. Electro Magnetic wave propagation in air can be divided in to
Two
WAVE PROPERGATION
Longitudinal
Transverse
6. There Are Two different ways which Electro Magnetic wave
travel from a Transmitting antenna to a Receiving antenna
RADIO WAVE
Ground wave
Sky wave
7. Ground wave is radio wave travel along
the surface of the earth.
They follows two distinct paths call Direct
path and Reflected path
8. Sky wave often call Ionospheric waves radiated in upward
direction and returned to earth at some distinct location due
to refraction
9. Skip distance is the distance from the transmitter to the point ware the sky wave is
first routed to the earth size of skip distance depend on Frequency , Incident angle
and degree of ionisation
10. Amount of refraction in ionosphere depends on three factors
Density of Layer
Frequency of radio wave
Angle at which wave enter to the Layer
11.
Troposphere- It has large variation
humidity and temperature but has only small effect
on electromagnetic wave at communication
frequencies.
Stratosphere- This has stable temperature
and humidity and has little effect on electromagnetic
wave at communication frequencies.
Ionosphere – This sphere has reasonably
stable
temperature but contain Electron and Ionised gas and has major effect
on propagation of MF and HF.
12. Ionosphere is the uppermost part of the
atmosphere it is ionised by the solar power or
the solar radiation. Ionosphere further
classified to D,E and F. During the day time F
layer split in to two as F1 and F2
The relationship between refraction index and
free electron density is defines as Maxwell’s
equation and it is as follows
n =
(1- 81N)
f2
n- Refractive index
N- Free electron density
f- Frequency of the electromagnetic wave
13. As free electron density rise , refraction index falls.
Hence refraction index varies with the F layer of Ionosphere
18. Listening and identifying radio frequencies transmitting by
other parties.
The DF systems using various techniques such as ; Adcock,
Doppler, Quasi-Doppler and associated multiple-element,
commutated (mechanical and electronic) arrays
