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Bars? Decibels? I Just Wanna Make a Phone Call!

Photo of a smartphone with a speedtest of LTE data.

Written by WiFiRanger Ambassador, Joel Weiss “docj”

From time to time most RVers find themselves in situations where making a simple voice call is difficult and using the Internet is PAINFULLY slooooow or impossible. It’s true that many of these issues start and end with signal strength from our device to the cell tower; but, how do we know for sure that’s the problem?

How Do We Measure Our Phones Actual Signal Strength?

Now at this point you might be saying, “Hey smart guy, that’s what those bars are for at the top of my screen!” Turns out those bars are not very useful when it comes to truly understanding the strength of the cellular signal your phone is receiving. The reason this is the case is that the bars are only a “relative” measure of signal strength and may or may not be calibrated to any particular physical measurement.

Stay with me now…

To put it differently, you can correctly assume that a “4-bar signal” is stronger than a “2-bar signal” on any particular phone; but, you have no way of knowing if four bars is actually twice as strong as two bars. Furthermore, a 4-bar signal on a Samsung Galaxy S10 may or may not show as 4-bars on a Google Pixel 3 or an iPhone 11 in the same location you’re parked. Therefore, when someone posts that they had a “4-bar signal” at XYZ Campground it doesn’t really tell the whole story. Now you may be asking, “If the bars are virtually meaningless what should I be using instead?” The answer is pretty simple:

You Need a True Measurement of the Cellular Signal (by decibels)

Ok, so how do you find that information? If you have an…

Photo of a smartphone with a speedtest of LTE data.
Cellular signal strength app

Alternatively, there are several free apps that’ll do it for you automatically with just a touch. One popular app is Network Cell Info Lite (screenshot above).

So What Do the Decimals Mean?

When Electrical Engineers measure signal strength they use negative numbers. So, smaller negative numbers indicate larger signal strength. Furthermore, the decibel unit they measure signals in is logarithmic which means that a signal of -94 dBm would be 10 times larger than the -104 signal I may have at any given moment/location. Every change of signal strength by 10 dBm is a factor of 10 increase or decrease.

Cellular signal strength graph

Below is a chart that helps illustrate these engineering measurements. The numbers on the sides of the triangle are cellular signal strength measured in decibels and the labels on the triangle correspond to the “quality” of that signal. Don’t forget that every change of 10 decibels is a factor of ten change in signal strength. Therefore, from the top of the chart at -80 dBm to the bottom at -130 dBm is a change of 500 decibels which corresponds to a change of 105 or 100,000.

When you’re at the bottom of the triangle (-130 dBm) you basically have no signal. You can try to use a cell booster/amplifier, or, a better antenna; but, success is never guaranteed no matter what you do in some locations. The best amplifiers on the market claim that they can increase the usable signal by 50 dBm; but, it’s more realistic to see an increase of -20 or -30 decibels. Don’t forget that if there is no signal at all no amplifier is going to help.

Don’t lose heart. Staying connected in the RV lifestyle is a challenge for us all. If staying online is essential during your travels just plan ahead so you’re not left without a signal.