参数资料
型号: ANT-418-PW-RA
厂商: Linx Technologies Inc
文件页数: 2/2页
文件大小: 297K
描述: ANT 418MHZ PRMNT SA 1/4 WAV WHIP
产品目录绘图: ANT-xxx-PW-RA
标准包装: 50
系列: RA - Antenna Factor
天线类型: 鞭状:1/4 波,旋转式,倾斜(直角)
频带数目: 1
频率: 418MHz(409MHz ~ 427MHz)
VSWR: 2
端子: 螺钉安装
安装类型: 底座安装
高度(最大): 5.18"(131.5mm)
包装: 散装
其它名称: ANT-418-RA
ANT-418-RA-ND
 2 
by
Data Sheet ANT-418-PW-RA
VSWR Graph
What is VSWR?
The Voltage Standing Wave Ratio (VSWR) is a measurement of how well
an antenna is matched to a source impedance, typically 50-ohms. It is
calculated by measuring the voltage wave that is headed toward the load
versus the voltage wave that is reflected back from the load. A perfect
match will have a VSWR of 1:1. The higher the first number, the worse the
match, and the more inefficient the system. Since a perfect match cannot
ever be obtained, some benchmark for performance needs to be set. In
the case of antenna VSWR, this is usually 2:1. At this point, 88.9% of the
energy sent to the antenna by the transmitter is radiated into free space
and 11.1% is either reflected back into the source or lost as heat on
the structure of the antenna. In the other direction, 88.9% of the energy
recovered by the antenna is transferred into the receiver. As a side note,
since the :1 is always implied, many data sheets will remove it and just
display the first number.
How to Read a VSWR Graph
VSWR is usually displayed graphically versus frequency. The lowest point
on the graph is the antennas operational center frequency. In most cases,
this will be different than the designed center frequency due to fabrication
tolerances. The VSWR at that point denotes how close to 50-ohms the
antenna gets. Linx specifies the recommended bandwidth as the range
where the typical antenna VSWR is less than 2:1.
Counterpoise
Quarter-wave or monopole antennas require an associated ground plane
counterpoise for proper operation. The size and location of the ground
plane relative to the antenna will affect the overall performance of the
antenna in the final design. When used in conjunction with a ground
plane smaller than that used to tune the antenna, the center frequency
typically will shift higher in frequency and the bandwidth will decrease.
The proximity of other circuit elements and packaging near the antenna
will also affect the final performance. For further discussion and guidance
on the importance of the ground plane counterpoise, please refer to Linx
Application Note AN-00501: Understanding Antenna Specifications and
Operation.
VSWR
Reflected Power
3:1
2:1
1:1
25%
11%
0%
418MHz
518MHz
318MHz
1.935
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