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How Cell Phone Signal Works & How Signal Boosters Work.

Watch video below providing detailed information about how cell phone signal works. Understanding this will automatically help us understand the concept of how installing a cell phone booster system helps. If you require professional installation, please submit details for a quote.


Today we're going to talk about understanding cellular signal. Having a good grasp on how cellular signal works will help out immensely with all aspects of setting up a cellular signal booster system. It all starts with outside signal. Knowing the outside signal strength will help you determine a number of things like, Is there enough signal to use a signal amplifier system? How much coverage can be expected from each amplifier? How many inside antennas can the amplifier support? How many total amplifiers will be needed? And what can your max cable lengths be?

Cellular signal is divided up into five frequency spectrums. Each of these spectrums is then divided into bands or channels. Each cell carrier owns and uses different bands and channels throughout the country. Cellular communication uses different channels for uplink and downlink within the same frequency. Uplink is a signal going to the tower. Downlink is a signal coming from the tower.

Increasing downlink is the main objective of the amplifier. Carriers use different bands to transmit different types of signal. If you look at the chart shown in video, you can see how it is broken down. Cellular or 800 megahertz is the most used band for cellular voice and 2G or 3G data like texts. PCS or 1900 is also used for this but to a lesser degree. LTE or 700 megahertz and AWS or 2100 megahertz bands are usually used for 4G data.

Some carriers are doing voice over AWS which our amplifiers will support as well. Higher frequency ranges are weaker than lower frequency ranges. The higher you get, the weaker the signal. For example, an incoming signal of negative 80 dB could provide enough coverage for up to 20,000 square feet on the LTE and cellular bands, but only up to 8000 square feet on the AWS and PCS bands.

When testing cell signals, we recommend using a signal meter instead of your phone in a test mode. Signal meters are great because you can cycle through all the various bands and frequency ranges on one device. Because carriers operate on different frequencies and you are installing a multi carrier solution, the only way to ensure performance is with a proper tool like a signal meter. A signal meter also updates instantaneously so you won't waste time waiting for the signal to update in each location.

Using your phone to test signal strength is less effective and reliable. Your phone takes a while to update the signal, sometimes up to a minute. Also, since your phone is tied to a carrier, it will only read the signal for that specific carrier and band it uses. There's no way on a phone to read all five frequency spectrums.

If you do want to use your phone, you can download the network signal info app for Android devices or you can put your phone into test mode for iOS and Android devices. On an iOS device dial,*3001#12345#* and press call. It will log into test mode. You can swipe down from the top of your screen and you'll see a signal reading in dB where the bars used to be. Android devices have similar features. You will find this in the settings menu. So now that we have convinced you why using a signal meter is more reliable when testing cell phone's signal strength, what do these readings actually mean?

Cellular signal is measured in decibel milliwatts or dBm and will always be displayed as a negative number. It ranges from about negative 95 dB being a very weak signal to negative 40 dB which is an incredibly strong signal as if you're standing next to a cell tower. Here're some good guidelines for signal strength levels coming into the booster and some tips on what to do in each case.

Anything stronger than a negative 45 dB for a Pro70 plus or a negative 55 dB for a Pro 70 is too strong a signal. This much signal coming into the signal booster will cause the spectrum to shut down on the amplifier. Keep in mind there are multiple bands or channels within each frequency spectrum. Even if just one band is overloading, the whole spectrum will shut down. To solve for this issue, you can find a location on the roof with less signal, use a directional antenna to aim it away from the cell tower or you can experiment with shielding the antenna to weaken the incoming signal.

Filters may also be a great choice to help you alleviate this problem. Negative 46 to negative 70 dB is the sweet spot. If you're getting signal readings within this range, the booster will provide a strong signal and the amplifier will be working at maximum performance. Negative 71 to negative 80 dB is fine for LTE and cellular bands. The coverage for PCs and AWS bands begins to diminish here. Consider using a higher gain donor antenna like YAGI directional. You will also need to keep cable runs at a minimum to limit signal loss.

Negative 81 to negative 95 dB coverage for all bands decreases significantly. The amplifier may only be able to support one broadcast antenna and cover less than 5,000 square feet total. Consider adding more amplifiers or pinpoint which frequencies are most important to the customer and determine a solution accordingly. Negative 95 DB and below doesn't leave you as much signal to work with. A signal amplifier system will still work but your coverage areas will be dramatically impacted. You will need to experiment with adding boosters and the placement of antennas to fulfil the customer's needs.

Now that you understand the signal readings and how they could affect the install, how do you know which band or channel a carrier is using?

Use the spectrum dashboard on the FCC's website. Use the map or enter your state and county manually in the boxes below, then you will see all the various carriers in that area and the bands and frequency ranges each is using. You can also apply various filters on the left of the screen to narrow down your search results even more. For example, you see here the At&T at this location is using band 12 which is a 734 to 746 megahertz in the 700 megahertz band, and channel B 1950 to 1965 megahertz in the PCS band.

We know which band are using by noting the frequency ranges used on the FCC website and cross-referencing that with this chart I showed earlier which shows which frequency ranges fall under each band. Knowing this information is important as it allows you to compare signal meter readings to determine the strength of each carrier signal at a site.

Finally, it is often helpful and sometimes crucial to find the location of the signal source or the cell tower. In situations a very strong signal, you can aim the outside antenna away from the cell tower to detune it and have less signal coming into the system. In situations of weak signal, you can point it directly at the cell tower for the strongest signal possible.

There are numerous ways you can find the location of a tower. Check our FAQ's link in the footer of all pages. We hope this helps you understand cellular signal and how it applies to installing a cellular amplifier system.