德国长度单位使用英尺吗_每英尺天线电缆长度损失多少Wi-Fi信号强度？

德国长度单位使用英尺吗

how-much-wi-fi-signal-strength-is-lost-per-foot-of-antenna-cable-length-00

If you are getting ready to add an antenna to your router in order to extend the Wi-Fi range in your home, just how long of a cable can you use? Does the cable’s length even matter? Today’s SuperUser Q&A post has the answer to a curious reader’s question.

如果您准备在路由器中添加天线以扩展家中的Wi-Fi范围，那么可以使用多长时间的电缆？电缆的长度是否重要？今天的“超级用户问答”帖子回答了一个好奇的读者的问题。

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

今天的“问答”环节由SuperUser提供，它是Stack Exchange的一个分支，该社区是由社区驱动的Q＆A网站分组。

Photo courtesy of Tyler Nienhouse (Flickr).

图片由Tyler Nienhouse(Flickr)提供。

问题 (The Question)

SuperUser reader Searock wants to know how much Wi-Fi signal strength is lost per foot of antenna cable length:

超级用户阅读器Searock想知道每英尺天线电缆长度会损失多少Wi-Fi信号强度：

I am thinking about buying an antenna for my router so that I can extend the Wi-Fi range in my home. I have been looking at some products like this one, for example: TP-Link TL-ANT2405C Indoor Desktop Omni-directional Antenna

我正在考虑为路由器购买天线，以便可以扩展家中的Wi-Fi范围。我一直在寻找类似的产品，例如： TP-Link TL-ANT2405C室内台式全向天线

The length of the cable is 130 centimeters (~51 inches). Is it OK if I increase the length of the cable or will it affect the potential range? What is the maximum length of cable that I can use?

电缆的长度为130厘米(〜51英寸)。如果增加电缆的长度可以吗，或者会影响电位范围吗？我可以使用的最大电缆长度是多少？

How much Wi-Fi signal strength is actually lost per foot of antenna cable length?

每英尺天线电缆长度实际上损失了多少Wi-Fi信号强度？

答案 (The Answer)

SuperUser contributor Jamie Hanrahan has the answer for us:

超级用户贡献者Jamie Hanrahan为我们提供了答案：

There is no arbitrary limit, but any increase in cable length will reduce signal strength. The connectors required to add another section of cable to the one shown will also have the same effect. As other commenters have noted, how much the signal strength is reduced for a given length depends on the cable and the frequency.

没有任意限制，但是电缆长度的任何增加都会降低信号强度。将另一部分电缆添加到所示电缆所需要的连接器也将具有相同的效果。正如其他评论者所指出的，给定长度的信号强度降低多少取决于电缆和频率。

A common, relatively inexpensive cable for short runs to a Wi-Fi antenna is LMR100. At 2.4 GHz (the common Wi-Fi band), 15 feet of LMR100 will result in a signal loss of about 6 dB. That is equivalent to dropping power down to just about 25 percent of what it was (each 3 dB equals a 50 percent gain or loss in power). With LMR400 cable, your loss would only be about 1 dB, but it is more expensive and also a lot less flexible (more difficult to install).

LMR100是用于短距离连接到Wi-Fi天线的常见相对廉价的电缆。在2.4 GHz(常见的Wi-Fi频段)下，LMR100的15英尺长将导致大约6 dB的信号损耗。这相当于将功率降低到原来的25％(每3 dB等于50％的功率增益或损耗)。使用LMR400电缆，损耗将仅为1 dB左右，但成本更高，灵活性也更低(安装更困难)。

The loss in dB is linear with a cable’s length. If you use 30 feet of LMR100 cable, the loss will be 12 dB (the signal will be about 1/16 of what it was). With 7.5 feet of LMR100 cable, the loss will only be 3 dB (about half of the signal’s strength). All of these numbers are for the 2.4 GHz Wi-Fi band. For the 5 GHz Wi-Fi band, it will be much worse.

以dB为单位的损耗与电缆的长度成线性关系。如果使用30英尺长的LMR100电缆，则损耗将为12 dB(信号约为其原值的1/16)。使用7.5英尺的LMR100电缆，损耗将仅为3 dB(约为信号强度的一半)。所有这些数字都是针对2.4 GHz Wi-Fi频段的。对于5 GHz Wi-Fi频段，情况会更糟。

Do not even think about using RG59 (the older, thinner coax cable that was used for TV cable/antennas and is commonly seen with “F” or “BNC” connectors attached; it is not even the right impedance) or RG58 (which has the right impedance, but is still very “lossy” at these frequencies). These cable types are not rated at all for use above 1 GHz.

甚至不要考虑使用RG59(用于电视电缆/天线的较旧，较细的同轴电缆，通常在连接“ F”或“ BNC”连接器时看到；甚至没有正确的阻抗)或RG58(具有正确的阻抗，但在这些频率下仍然非常“有损”。这些电缆类型根本不适合在1 GHz以上的频率下使用。

You can find data sheets with signal loss graphs and calculators for various types of microwave coax cable all over the Internet. Here is a calculator (found at a cable dealer’s website) that covers a wide variety of cable types. And to convert dB to power ratios (or back), try this decibel calculator. Keep in mind that since this is signal loss we are talking about, make sure to enter the dB as a negative number before pressing the calculate button. Also note that you want the power ratio, not the voltage.

您可以在Internet上找到带有信号损耗图的数据表和各种类型的微波同轴电缆的计算器。这是一个涵盖各种电缆类型的计算器 (可在电缆经销商的网站上找到)。并将dB转换为功率比(或反向)，请尝试使用此分贝计算器。请记住，由于这是我们正在讨论的信号损失，因此在按下计算按钮之前，请确保输入dB作为负数。还要注意，您需要功率比，而不是电压。

One last tip. Do not try to assemble cables yourself. Buy cables with the right connectors already attached. What may seem like very minor mistakes with connector assembly can cause huge losses at these frequencies. And absolutely do not cut the connectors off and try to splice the coax. You might as well throw the antenna away at that point.

最后一个提示。不要尝试自己组装电缆。购买已连接正确连接器的电缆。在这些频率下，连接器组件出现的细微错误似乎会造成巨大损失。绝对不要切断连接器，并尝试将同轴电缆拼接起来。您最好在那时将天线扔掉。

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

有什么补充说明吗？在评论中听起来不错。是否想从其他精通Stack Exchange的用户那里获得更多答案？在此处查看完整的讨论线程。