When you are setting up a long range Wi-Fi connection, you want to make sure that your connection is as solid as possible, but can you use a mixture of antenna types or should you go with high-gain only? Today’s SuperUser Q&A post has the answers to a confused reader’s question.
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.
Photo courtesy of Karlis Dambrans (Flickr).
SuperUser reader userpal wants to know if he needs to have high-gain antennas on both ends of his long range Wi-Fi connection:
I am trying to understand how long range Wi-Fi works. As far as I know, Wi-Fi consists 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 transmit 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 conditions, can the laptop actually connect to the AP?
Wi-Fi diagram courtesy of Freeman’s Garage Blog.
Does userpal actually need high-gain antennas on both ends of his long range Wi-Fi connection or not?
SuperUser contributors mgjk, Jamie Hanrahan, and David Cary have the answer for us. First up, mgjk:
The antenna changes the shape of the transmission. The electrical signal does not become more powerful, but less is wasted during transmission in directions 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 response. The person at the other end does not need any special equipment, but you have increased the range and sensitivity.
Followed by the answer from Jamie Hanrahan:
High-gain antennas provide gain on both transmitting 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.
And our final answer from David Cary:
You might also mention antenna reciprocity — if a directional antenna can transmit 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.
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.