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What is strong and weak signal in dBm for 3G vs. 4G?

Apr 29, 2016

What is strong and weak signal in dBm for 3G vs. 4G?

Having an accurate measurement of signal strength in decibels (dBm) is crucial when installing your cell phone signal booster system. Decibels accurately measure the signal strength you are receiving.

How do you measure it?

How to measure signal strength in dBm on iPhone:

Dial *3001#12345#* then press Call.

  1. Hold down power button until you see, "Slide to Power Off".
  2. Then release the power button.
  3. Hold the Home button until your main screen appears.

If you want to check 3G/1x network signal strength but your iPhone is picking up 4G/ LTE signal, go to Settings > Cellular > Cellular Data Options > Enable LTE > Select Off. This will force your phone to use 3G network.

How to measure signal strength in dBm on Android Phones:

Settings > About Phone > Status or Network > Signal Strength or Network Type and Strength (exact options/ wording depends on phone model).

Checking on All Phones:

  • Keep track of the network (3G or 4G) phone is connected to.
  • Any signal readings you take are valid for that phone's carrier. To get readings from other carriers, you will need phones from each carrier.
  • When system is set-up, you can easily revert back to the "bar display" by dialing *3001#12345#* press Call, press the signal strength at the top left of screen to toggle between numbers and bars, then press the Home button to exit Field Test mode.

Now on to the main topic: Differences Between 3G / 1x versus 4G / LTE signal strength in dBm.

Signal strength in dBm on 3G does not work the same way as on 4G/LTE. The numbers are basically a bit skewed such that the quality of voice and data transmission is better on 4G due to its efficiency and therefore the signal can be worse but the service would fare comparatively better on 4G than on 3G. See below for explanation in conjuction with the image shown at the top.

Excellent: As you can see in image above, -70 dBm on a 3G network is considered excellent signal strength versus -90 dBm on 4G or LTE network which is also considered excellent.

Good: Similarly, -71to-85 dBm on 3G is considered good and so is -91 to -105 dBm on 4G/LTE.

Fair: -86 to -100 dBm on 3G is fair and -106 to -110 dBm on 4G/ LTE is also fair.

Poor: -101 to -109 dBm on 3G is poor and -111 to -119 dBm on 4G is poor.

Dead Zone: -110 dBm on 3G network is practically a dead zone, and so is -120 dBm on 4G LTE network.

What is minimum signal strength needed outside for cell booster to generate usable signal inside?

Please see the beginning number in the chart at the very top under the column, "Poor". If the value you get when you check your best signal strength anywhere on the perimeter or on top of your house/ building where you can mount an antenna is close to -101 dBm on 3G network and/or -111 dBm on 4G LTE network, then the cell phone booster should work to provide needed signal strength to make and hold a call inside, as long as you choose the highest dB Gain signal amplifier kit such as our maximum 70 or 72 dB Gain amplifiers. Or in laymans terms, if you can make and hold a call in a spot outside the house where you can install exterior antenna, then the most powerful signal booster with 65-72 dB signal amplifier (depending on frequency band) or preferably max 72 dB signal amplifier will enable you to do the same, or a lot better, easily, inside the house/ building.

Did you know?

What is the big deal about some signal boosters that offer just 2 or 3 dB higher Gain than another? Well, a signal increase of just 3dB is 2 times the power and signal amplification!

Signal increase of just 3dB is 2 times the power!

Until next time,


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