What factors affect propagation?
Factors affecting radio propagation The properties of the path by which the radio signals will propagate governs the level and quality of the received signal. Reflection, refraction and diffraction may occur. The resultant radio signal may also be a combination of several signals that have travelled by different paths.
What is ionospheric propagation?
Ionospheric Propagation. The ionosphere exists between about 90 and 1000 km above the earth’s surface. Radiation from the sun ionizes atoms and molecules here, liberating electrons from molecules and creating a space of free electron and ions.
Which one is used in ionospheric propagation?
HF propagation & skywaves When using HF propagation via the ionosphere, the radio signals leave the transmitting radio antenna on Earth’s surface and travel towards the ionosphere where some of these are returned to Earth.
What is propagation frequency?
Lower frequency (between 30 and 3,000 kHz) vertically polarized radio waves can travel as surface waves following the contour of the Earth; this is called ground wave propagation. At even lower frequencies, in the VLF to ELF bands, an Earth-ionosphere waveguide mechanism allows even longer range transmission.
How is ionosphere ionized?
The ionosphere is ionized by solar radiation. It plays an important role in atmospheric electricity and forms the inner edge of the magnetosphere. It has practical importance because, among other functions, it influences radio propagation to distant places on the Earth.
What is critical frequency of ionosphere?
Critical frequency is the highest magnitude of frequency above which the waves penetrate the ionosphere and below which the waves are reflected back from the ionosphere. It is denoted by “fc”. Its value is not fixed and it depends upon the electron density of the ionosphere.
What is the best layer for ionosphere?
F layer. The F layer or region, also known as the Appleton–Barnett layer, extends from about 150 km (90 mi) to more than 500 km (300 mi) above the surface of Earth. It is the layer with the highest electron density, which implies signals penetrating this layer will escape into space.
How does ionosphere affect the propagation of radio waves?
The ionosphere contains a high proportion of free electrons which influence radio propagation. High Frequency (HF) radio waves hitting the free electrons in the ionosphere cause them to vibrate and re-radiate the energy back down at the same frequency, effectively bouncing the radio wave back towards the Earth.
What is the frequency range of RF?
Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz.
What is the most important factor for plants to grow?
There are four primary factors that affect plant growth: light, water, temperature and nutrients. These four elements affect the plant’s growth hormones, making the plant grow more quickly or more slowly. Changing any of the four can cause the plant stress which stunts or changes growth, or improves growth.
What causes attenuation by gases for wave propagation?
Attenuation by gases for W/V bands is primarily caused by oxygen and water vapor. A method for predicting absorption due to atmospheric gases is given in [2]. Figure 1 shows the effect of oxygen and water vapor to wave propagation in different frequencies.
Which HF bands do not support ionospheric propagation?
At the low point of the cycle, HF bands above 20 MHz or so may not support ionospheric propagation. At or near the 11-year peak, frequencies at 50 MHz and higher may be effective. Signals in the medium and shortwave bands travel by two basic means: ground waves and sky waves.
How much attenuation does the cloud cause propagation loss?
Cloud attenuation at the W/V bands can contribute to significant loss (> 10 dB). Rain attenuation has the most dominant contribution to the total propagation loss when dealing with higher frequencies.
How do you calculate minimum attenuation?
Minimum attenuation occurs between these frequencies. To calculate the gaseous attenuation, the parameters are needed are elevation angle, operating frequency, altitude above sea level, and water vapor density, and the attenuation equation can be found in [2].