1. Perpendicular antenna What perpendicular antenna uses in the radio equipment that monitor is very much.
Perpendicular antenna is actually a kind occasionally extremely child aerial. Occasionally extremely aerial is comprised by two conductor, every are 1/4 wavelengh, namely aerial total length is half wavelengh. So Ou Zitian line calls half brace up child.
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Occasionally extremely the Zhenzi of aerial is OK horizontal position, also but perpendicular position. Its directional graph is semmetry with feed dot. Feed dot is in half brace up child center. The impedance that feed nods is pure resistor, approximate 75 Ω () of about 73 Ω . If grow the Zhen Ziyan of two 1/4 wavelengh to be folded again,return a center, join together, became a fold idol extremely child aerial, abbreviation fold brace up child.
Fold idol extremely child the impedance of aerial also is pure resistor approximate 300 Ω () of about 290 Ω , show taller input impedance, the tall block that constitutes with line of parallel make a present of transmits aerial to get applying in a lot of circumstances.
Occasionally extremely child aerial straighten, perpendicular at the ground, become perpendicular antenna. If " take out " lower 1/4 λ brace up child, become asymmetry perpendicular antenna, this kind of circumstance is to be based on two hypothesis: ① ground is " lens face " , there is 1/4 λ below the ground brace up child " mirror " ; ② brace up child leave the ground to have enough high H. Normally H>3 λ . Commonly used perpendicular antenna is asymmetry antenna, in the level up isotropy.
A kind of special perpendicular antenna, 1/4 λ brace up child radiation implement bottom still has 4 radial unit. It is used at rice and 80 meters of 40 frequency paragraph the ionosphere with have better reflexes the effect. This kind of antenna has a special name to call Makeni aerial. The antenna that the receiver such as R7000 configures belongs to this kind of antenna.
2. 8 wood antenna A kind of handy directional antenna, it has an incentive sheet, other unit serves as respectively bring to use with reflection, it can be being brought to directional assemble energy to form beam. This kind of antenna cries bundle shoot aerial. Typical bundle shooting aerial is 8 wood antenna.
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The reflector of 8 wood antenna and director draw drive brace up child the certain energy that radiation gives, next again radiation goes out, it is certain to form directional. Incentive Zhen Zichang uses fold idol extremely child, the dimension of reflector grows slightly at 1/2 λ ; Gong Xiangqi's dimension slightly short at 1/2 λ .
Interval all makes an appointment with 0.15 λ left and right sides. The unit amount of 8 wood antenna is more, its are being jumped over to gain big, the gain of 3 unit makes an appointment with 7dB. Before cable television gains ground, antenna of apical of urban country house blast, it is 8 wood antenna mostly.
3. Kasaigelun the reflection unit of 8 wood antenna mixes aerial be being brought to what unit emerges to be brought to the effect is finite, and it goes up in a face only, want to form true beam in stereo space, need the reflector of a sunken form. Effective appearance is cut paraboloid reflector.
If be on the focus of paraboloid reflector, the protruding reflector that installs a hyperboloid (deputy reflector) , source letting make a present of first to deputy reflector radiate, through deputy reflector reflection arrives on paraboloid, reflex 2 times by paraboloid reflector again go out, will get at this moment one cylindrical beam. Position of mobile deputy reflector, can change focusing. This kind of antenna has a special name, call Kasaigelun aerial.
If will be made,4 photographs eye accuses an antenna many same occasionally extremely child aerial discharges. Control every by order through the computer occasionally extremely child feed is high frequency the starting phase of signal, can make beam is in appoint direction to sweep sweep past. Our country is in on century 70 time metaphase, one is built in China north area a face for 20*5 rice the photograph of 2 accuses a radar, a side in hill body secures its antenna to be not moved, beam however can controlled scanning.
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