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On a SMA High gain antenna does the lower the dbi the better the reception.?

Answers:1   |   LastAnswerAt:2009.12  

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adan976g 
Asked at 2009.12.20 06:50:47
No, just the opposite actually. Higher dBi means the RF energy is more focused. A standard antenna might be roughly 2.2dBi and the RF energy pattern is shaped like a giant 100-foot donut. If you use a high gain antenna, the energy gets more flattened out, now shaped more like a 200-foot pancake. So a high gain (like a 5dBi) has less signal going up/down but a stronger signal that goes farther out to the sides. This might actually make some setups WORSE, such as an access point in a basement and a laptop up in a 2nd floor bedroom for example.

Higher gain is bidirectional, that is, the transmitted energy is stronger (more focused) and its receive sensitivity is also stronger. Every increase by 3dBi is a doubling of power. Every increase of 10dBi is 10 times the power. That's the rule of 3's and 10's, it's logarithmic. The rule of thumb is that every increase by 6dBi will about double your distance outdoors, and 9dBi will about double your range indoors.

Note, I made the point above (more focused) to stress that a high gain antenna is an example of PASSIVE gain. This is not active gain, nothing is being amplified and the access point puts out the same amount of output power. The passive gain is accomplished by the antenna focusing down the RF energy pattern. So picture it like the same amount of signal, but shaped a different way. A very simple mental picture is to think of a large round balloon that gets squeezed on the top and bottom. Same amount of air (signal) in the balloon, but now it reaches out further to the sides and less going up/down.
answer networkmaster  Answered at 2009.12.20 06:50:47
No, just the opposite actually. Higher dBi means the RF energy is more focused. A standard antenna might be roughly 2.2dBi and the RF energy pattern is shaped like a giant 100-foot donut. If you use a high gain antenna, the energy gets more flattened out, now shaped more like a 200-foot pancake. So a high gain (like a 5dBi) has less signal going up/down but a stronger signal that goes farther out to the sides. This might actually make some setups WORSE, such as an access point in a basement and a laptop up in a 2nd floor bedroom for example.

Higher gain is bidirectional, that is, the transmitted energy is stronger (more focused) and its receive sensitivity is also stronger. Every increase by 3dBi is a doubling of power. Every increase of 10dBi is 10 times the power. That's the rule of 3's and 10's, it's logarithmic. The rule of thumb is that every increase by 6dBi will about double your distance outdoors, and 9dBi will about double your range indoors.

Note, I made the point above (more focused) to stress that a high gain antenna is an example of PASSIVE gain. This is not active gain, nothing is being amplified and the access point puts out the same amount of output power. The passive gain is accomplished by the antenna focusing down the RF energy pattern. So picture it like the same amount of signal, but shaped a different way. A very simple mental picture is to think of a large round balloon that gets squeezed on the top and bottom. Same amount of air (signal) in the balloon, but now it reaches out further to the sides and less going up/down.
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