SILO 3.3 Radio communication systems

Question 1

What are the characteristics of VLF ?

Answer 1

3-30 kHz : ground wave and under water wave. Skywave is perfectly reflected. Consume high power.

Question 2

What are the characteristics of LF ?

Answer 2

30-300 kHz : ground wave. skywave is attenuated. Not affected by the ionosphere.

Question 3

What are the characteristics of MF ?

Answer 3

300-3000 kHz : ground wave and unreliable skywave (only during night).

Question 4

What are the characteristics of HF ?

Answer 4

3-30 MHz : short ground wave, skywave can reach long distance, but are subject to ionospheric conditions.

Question 5

What are the characteristics of VHF ?

Answer 5

30-300 MHz : Direct LOS. good quality all day.

Question 6

What are the characteristics of UHF ?

Answer 6

300-3000 MHz : Gound-Air microwave.

Question 7

What are the characteristic of SHF ?

Answer 7

3-30 GHz : LOS, subject to atmospheric perturbations.

Question 8

What are the characteristics of ELF ?

Answer 8

30-300 GHz : Upper link on satellite and short distance local network.

Question 9

Name the 4 propagation modes of ground wave.

Answer 9

Direct, ground reflected, surface and sky.

Question 10

What are forward Scatter Reflection ?

Answer 10

Scattering in the Ionosphere (25-60 MHz) or the troposphere (300 MHz to 8 GHz) scatter the wave back to the ground.

Question 11

Explain Radio communication by skywave.

Answer 11

LF, MF and HF. Not very mobile. Extensive antenna parks.

Question 12

Explain CNR.

Answer 12

HF, VHF and UHF. FH possible. Easy to jam/detect. OMNI antennas. In line crypto.