sky wave การใช้

• At shorter distances, only the first hop sky wave is of importance.
• Sky wave propagation occurs in the waveguide formed by the ground and ionosphere, each serving as reflectors.
• Across the street, hundreds gathered under sunny skies waving Syrian flags, dancing to drums and singing national songs.
• The inversion effectively reduces sky wave refracted over the horizon rather than continuing along a direct path into outer space.
• Covered are topic such as wavelength, frequency, nature and propagation of radio waves; ground and sky waves; skip distance; and fading.
• Across the street, hundreds of people gathered under sunny skies waving Syrian flags, dancing to the beat of drums and singing national songs.
• The last interference minimum on the ground ( z = 0 ) between the ground wave and the first sky wave is at a horizontal distance of
• Within this region, no signal can be received because, due to the conditions of the local ionosphere, the relevant sky waves are not reflected but penetrate the ionosphere.
• HF communications are in the 2-30 MHz band, which provides Beyond Line-Of-Sight ( BLOS ) communication ( HF Sky Wave or HF Ground Wave ) optimized for transmission up to.
• That reflected wave, with its phase reversed, can either cancel or reinforce the direct wave, depending on the antenna height in wavelengths and elevation angle ( for a sky wave ).
• When a sky wave is launched by such an antenna, that phase shift is always significant unless the antenna is very close to the ground ( compared to the wavelength ).
• A skip zone is an annular region between the farthest points at which the ground wave can be received and the nearest point at which the refracted sky waves can be received.
• When using medium to high frequency radio telecommunication, there are radio waves which travel both parallel to the ground, and towards the ionosphere, referred to as a ground wave and sky wave, respectively.
• It can be mitigated to some extent by the use of a tall mast radiator of up to about 0.6 wavelengths height, which increases the ground wave field strength while reducing high-angle sky wave radiation.
• The sum of ground wave and first hop wave displays an interference pattern with interference minima if the difference between the ray paths of ground and first sky wave is half a wavelength ( or a phase difference of 180?).
• This led to the 1919 introduction of the Adcock antenna ( UK Patent 130, 490 ), which consisted of four separate monopole antennas instead of two loops, eliminating the horizontal components and thus filtering out the sky waves being reflected down from the ionosphere.