A cellphone signal booster that really works (San Diego Transcript)

I’ve been trying out a product that’s designed to improve cell service, both data and voice, in the home. It’s called the Cel-Fi Duo Signal Booster from Nextivity, a San Diego-based technology company.

I’m using the model designed for T-Mobile cellular phones. A second version is available for AT&T phones. While there are not yet models for Verizon or Sprint, the company produces models that work with 170 carriers around the world.

I began as a skeptic because I’ve tried so many products over the years that claim to boost cellular reception, but rarely did they work well enough to detect any improvement. But this product is different. It really works and its performance exceeded all expectations.

The Cel-Fi consists of two boxes that stand on end, each about the size of a small router. The concept is to locate one of the boxes, called the Network Unit, in the home where the signal strength is the strongest, and the other box, called the Coverage Unit, where the signal is the weakest.

In operation, the Network Unit searches for cellular signals from your carrier’s three nearby cellular base stations, and figures out which one is the best for noise characteristics and has the least signal loss, all in less than 20 milliseconds. It then sends that cellular signal over a wireless frequency, similar to Wi-Fi, to the Coverage Unit, which then rebroadcasts that cellular signal from the weakest area of the home.

The company notes that Cel-Fi is the only consumer booster with up to 100 decibels of gain approved by the FCC, allowing one system to cover up to 13,000 square feet, or a two-story home about 100 by 60 feet in size.

Like most wireless specs, the coverage depends on the number of walls and other construction factors that may reduce the signal’s penetration. Hey, I’d be happy if it would work over an area of 2,500 square feet.

My home is a one-story ranch with a U-shaped layout. At one end of the U is large open living room with floor-to-ceiling windows. At the other end is the master bedroom. In between are hallways and other bedrooms, a bath and my office, which gets the worst reception, probably because it’s buried in the middle of the house.

Before setting up, I walked around my home noting how many bars my phone, an iPhone 6 Plus, displayed to find the strongest and weakest areas of reception. The phone display ranged from one to three bars: three bars in the living room near the windows, just one bar in my office and one or two bars everywhere else.

Setting up was simple and straightforward. I plugged the Network Unit into an outlet on the wall next to the large windows and stood it on the floor against the baseboard, tucked behind a chair. Its own built-in display indicated four green bars.

I then plugged in the second box, the Coverage Unit, in my office where the signal was the lowest. The number 9 was displayed, indicating a strong signal was being received. The instructions ask you to find a spot that is at least 8.

I was curious to see what the cell signal measured on my phone. I repeated the walk around and found the number of bars, originally ranging from one to three, now read mostly four or five, with an occasional three. By the numbers, the improvement was very impressive.

I used the phone for several days, and the phone worked really well — no dropped or staticky calls and very clear conversations. I measured the download speed during a time when the networks were not likely to be busy, using a neat free app OpenSignal.

With the Cel-Fi active, download and upload speeds averaged about 15 Mbps. With the Cel-Fi unit disconnected, the download was about 8 to 10 Mbps and the upload with a meager 0.6 Mbps.

I also measured the signal strength on my phone to be -74 dB with Cel-Fi on and -118 dB with it off, an improvement of 44 dB.

There are also a couple of side benefits. Because of the strong signal, the phone doesn’t need to run at its maximum power; thus battery life is extended, and the phone emits less radiation.

This is a very impressive product: easy to set up, easy to use and the improvement in performance speaks for itself. The product sells for about $500, and is well worth it if you have unsatisfactory cell service at home.

Equally important: If you’ve hesitated to get rid of your landline because of marginal cellular service, now there’s less of a reason to hold back. (www.cel-fi.com).

by Phil Baker