What is the limitation of having bigger antenna?
A disadvantage of extreme gain antennas is that they can be very sensitive to improper position displacement due to wind conditions. There are a variety of configurations that can result in good directional RF signal transmission, including Yagi antennas, dish antennas, Luneberg lenses, and phased arrays.
What is called critical frequency?
Critical Frequency Formula. Radio frequency waves propagate between transmitter and receiver using antennas. The radio frequency at or below, the wave gets reflected from ionosphere and above this frequency waves penetrate through ionospheric layer. This is frequency is known as critical frequency.
How does antenna size affect gain?
As a practical matter, the maximum directive gain (directivity) of an antenna depends upon its physical size compared to wavelength. The uniformly illuminated aperture type of antenna has been found to give a higher gain in practice than other antennas, at least for large apertures.
How can I increase my antenna efficiency?
If concern is antenna efficiency then material losses (copper or dielectric losses) are an important factor. You can apply reflecting surfaces, active component, EBG structure or slot matching etc to improve radiation efficiency.
What is dBi in antenna?
The expression dBi is used to define the gain of an antenna system relative to an isotropic radiator at radio frequencies . The symbol is an abbreviation for “decibels relative to isotropic.” The dBi specification is based on the decibel , a logarithm ic measure of relative power .
What is critical frequency & skip distance?
The skip distance is dependent upon a variety of factors: Frequency: The frequency of operation has a major influence on the skip distance that can be achieved. Typically as the frequency increases a lower angle of radiation is needed to return the signals to Earth in a shorter distance.
What is a good antenna efficiency?
An ideal antenna has 100% antenna efficiency i.e., it transmits all the power fed to it. But in the real world, a good antenna radiates only 50 to 60% of power supplied to it.
What determines antenna bandwidth?
– Bandwidth The bandwidth of an antenna refers to the range of frequencies over which the antenna can operate correctly. The antenna’s bandwidth is the number of Hz for which the antenna will exhibit an SWR less than 2:1. The bandwidth can also be described in terms of percentage of the center frequency of the band.
What is LUF and MUF?
MUF is a median frequency, defined as the highest frequency at which skywave communication is possible 50% of the days in a month, as opposed to the lowest usable high frequency (LUF) which is the frequency at which communication is possible 90% of the days, and the Frequency of optimum transmission (FOT).