如果一端沒有使用高增益天線，長距離wi-fi連線能否工作？

當您設定遠端Wi-Fi連線時，您希望確保您的連線儘可能牢固，但是您是否可以使用多種天線型別的混合天線，還是隻使用高增益天線？今天的超級使用者問答有一個困惑讀者的問題的答案。...

當您設定遠端Wi-Fi連線時，您希望確保您的連線儘可能牢固，但是您是否可以使用多種天線型別的混合天線，還是隻使用高增益天線？今天的超級使用者問答有一個困惑讀者的問題的答案。

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

照片由Karlis Dambrans（Flickr）提供。

問題

超級使用者讀者userpal想知道他是否需要在遠端Wi-Fi連線的兩端安裝高增益天線：

I am trying to understand how long range Wi-Fi works. As far as I know, Wi-Fi c***ists of Rx and Tx. When a laptop is connected to an AP, the laptop is able to receive data from the AP (Rx) and also tran**it data back to the AP (Tx).

Suppose I want to build a long range Wi-Fi setup to cover a large area and I connect a high-gain omni-directional antenna like the one shown in this diagram to the AP.

So assume that the original AP’s Wi-Fi signal radius is 250 meters, but by using the high-gain antenna, the radius become 1,000 meters.

At 1,000 meters away from the AP and using a normal laptop (without a high-gain antenna), I try to connect to the AP. The signal from the AP is able to reach the laptop, but the signal from the laptop should not be able to reach the AP. Under these conditi***, can the laptop actually connect to the AP?

Wi-Fi diagram courtesy of Freeman’s Garage Blog.

使用者是否真的需要高增益天線兩端的遠端Wi-Fi連線與否？

答案

超級使用者貢獻者mgjk、Jamie Hanrahan和David Cary為我們提供了答案。首先，mgjk：

The antenna changes the shape of the tran**ission. The electrical signal does not become more powerful, but less is wasted during tran**ission in directi*** which are not useful (i.e. up and down).

Similarly with reception, the signals are received from a more narrow field, which strengthens reception and reduces interference.

It is similar to talking through a cone, then listening through the cone for a resp***e. The person at the other end does not need any special equipment, but you have increased the range and sensitivity.

接下來是傑米·漢拉漢的回答：

High-gain antennas provide gain on both tran**itting and receiving. So, with such an antenna at only one end, you will get more range than with a standard antenna at each end, but less than with a high gain antenna at both ends.

大衛·卡里最後的回答是：

You might also mention antenna reciprocity — if a directional antenna can tran**it four times as far as a standard antenna, then the same directional antenna can receive from four times as far away as a standard antenna.

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