Getting Maximum Coverage With Your Wi-Fi

If only our homes or apartments were built keeping in mind the optimal wifi router location, we wouldn’t have had this problem. Arbitrarily placed, lying in a corner, is your one true friend in this lockdown, helping you access loads of content online. But more often than not, we do end up in situations where the wifi signal is patchy causing frequent connection drops, fluctuating network speed and well frustration. What if there was a way to improve signal with a simple hack, without opting for range extenders?

Some background to the problem. My elder brother in R1(fig below) is not getting decent wifi connection, and gets frequent connection drops. With WFH as the only mode of working nowadays, one can imagine frustration of having to reconnect VPN, after every connection drop.

A typical home router is set to output 100mW of max power as per CE norms. Most of them are configured to output max power as default option. This power suffices to penetrate two wall layers and provide a decent coverage. There is reflection of signals from the walls , but that is irregular, and wall absorbs lot of power. A signal in LOS is always preferable. Well as one can see, R1 is 3 walls away, and path through wall-to-wall reflection is also well, not that straightforward 😊

A router antenna is omnidirectional, meaning it is transmitting equal power in every direction. But there are only certain areas in house where you need wifi to work!, so an omnidirectional antenna might not be best for every case. What if the antenna power can be channeled to direct more power in the path of R1 and reduce power from green zones?. As we don’t need wifi signals outside our home, so minimizing power seeping out of home is the first step.

Based on the requirements, I decided, I definitely need strong signal in R1 and R2. Hall is where router is placed, and devices are in LOS of the router, so I don’t need to plan for Hall. I can however reduce power going to kitchen, and outside, as these are less priority areas.

Currently, there are several videos of making can antennas online, by placing soda can behind the router, but can it be optimized?

So, taking everyone back to school physics, if a radiating object is placed at focal point of a parabola, then the reflected rays are always parallel to the the principal axis. Using this concept, It makes sense to have a parabolic reflector. Since antenna is a dipole, extending in vertical direction. We would need to extend our parabola in same direction as well, meaning a rectangular parabola. Something like the image on the left.

Now what should be the focal length of the parabola? To understand this let’s consider the path of the signal from router to the parabola surface (now would be a good time to google for path length and phase difference relationship 😊)

The dot in orange is the antenna and the reflector is placed behind it. The reflected wave will travel additional 2x distance to reach antenna , the reflection surface would give a phase shift of 180 degrees to the incident wave. 180 degrees of phase shift means λ/2 in path length terms. λ is the wavelength of signal.

To cause a constructive superposition at the antenna , it is important that the reflected waves reach in phase with the original waves. If the 2x distance equals λ/2, then the extra distance covered by reflected waves equals λ. So, x should be λ/4.

At 2.4GHz, λ = 12cm (nearly) . So if the reflector is placed 3 cm behind the antenna it would be ideal!

By similar means, it works while receiving signals from the device at the router. The reflectors essentially capture the incoming signal at bigger area and direct it to antenna.

Armed with these calculations, I printed 4 reflector shields, lined them up with aluminium foil and put it behind the router, and voila! It worked!. I could see a 10-12 db jump in signal levels straight away!, whats important is that the signal levels are now stable, and are not varying over time (which can happen with wall reflected signals)

It’s optimal but not must to use parabolic reflectors, but the distance from antenna matters!. You can see a change by putting a reflecting disk (say a CD) behind antenna as well! It has been 2 days since I put the reflectors behind the routers, the coverage in R1 has improved, and importantly they are no connection drops as of yet 😊 Sharing some results below:

Notice the change in signal strength of 5G signal, and 2.4GHz signal. This was measured very close to router, to minimize any attenuation in the air. This shows that the reflectors do indeed work! and here's what my router looks like now :)