The Cell Phone Signal Booster Guide

So you need a cell signal booster? We're here to help! This is our definitive, 7,000+ word guide on exactly how to find the right kit and get more bars.

This guide has two parts:

We start with our product recommendations, but we also strongly urge you to read Part 2: The Signal Guide as well. The Signal Guide contains essential information that'll help you understand how your phone and signal boosters work together.

We’re constantly updating this document to make sure it includes the latest products and what we learn from selling and installing these devices.

The last update to this guide was on December 3rd, 2017, and the next scheduled update is on January 8th, 2017.

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Signal Boosters For Homes and Small Offices up to 5,000 sq ft

The booster we recommend for homes and small offices depends on the signal strength outside your building. If you don't know the signal strength (measured in dBm), outside your building, start by reading this part of our guide.

If you have strong signal outdoors of over -70 dBm, skip down to our recommendations for users with strong outdoor signal. If you have weak outdoor signal (less than -80 dBm), read on below.

If you have weak outdoor signal (less than -80 dBm):

A cellular signal booster works by amplifying signal from a “donor” antenna. The donor antennna is usually installed outdoors, often on the roof. If signal outdoors is weak the coverage area of the booster will depend on the amplification, or the “gain,” of the signal booster kit you use.

If signal is weak outside, you'll need a lot of gain to cover your entire home or office. The gain of your booster kit comes primarily from two components: the amplifier and the outdoor donor antenna. Most boosters are limited to between 64 dB and 72 dB gain by the FCC, however, single-carrier devices can amplify signal by up to 100 dB.

Directional antennas, such as “yagi antennas,” provide higher gain by targeting signal reception in one direction. The end result is a stronger signal for your booster to amplify, and thus better coverage. There’s more information on choosing antennas below.

Our top pick: only boosts one carrier at a time, but offers 100 dB gain

If you have weak signal outside the building and only care about boosting one of either AT&T, Verizon or T-Mobile, the best choice is the new Cel-Fi GO X. Released in June 2017, the GO X is a "single-carrier" booster that is approved by the FCC to offer up to 100 dB of gain. The GO X is a single-carrier booster: it will only amplify the signal from one carrier's network at a time.

The higher gain of the GO X compared to other boosters makes it perfect for areas with weak outdoor signal. With 13 dBm downlink power, the GO X can also cover a relatively large area with improved signal. A single indoor antenna should get you up to 1,000 square feet of coverage, but you can use one of our multiple-antenna kits to expand coverage up to 5,000 square feet.

Two important caveats: first, there is no support for Sprint. Second: for Verizon users, the Cel-Fi Go X only amplifies LTE signal. Almost every phone sold in the last 3 years supports Voice over LTE (VoLTE), but if you have an older phone that doesn’t support VoLTE, you’ll only see a boost in data rates and no improvement for calls.

Our favorite "broadband" signal boosters that work with multiple carriers (including Sprint)

If you have weak outdoor signal and need coverage for multiple carriers or for Sprint, the best signal booster options are either the Hi-Boost Home 15K or the SureCall Fusion4Home. Both units are limited to the 64 dB to 72 dB gain limit set by the FCC.

The Hi-Boost Home 15K offers excellent value for money, with performance comparable to much more expensive systems like the Wilson Pro 70 Plus. If you use multiple indoor antennas, you can cover up to 2,000 square feet with better signal. Of course, if your budget allows, more expensive systems like the SureCall Force5 2.0 or the Wilson Pro 1000 are definitely better options.

The Fusion4Home is a budget option, and you shouldn’t expect to cover more than a few hundred square feet (or 1-2 rooms). We strongly recommend using the kit with a directional outdoor antenna and a panel indoor antenna–you can read more about why here.

If you have strong outdoor signal (4-5 bars):

It’s frustrating: coverage outdoors is great, but your building materials prevent signal from getting into your home or office. But no need to worry - this kind of situation is actually where signal boosters work best.

Your main consideration when picking an amplifier should be the downlink output power of the signal booster. Since signal outside is strong, you're very likely hit the maximum downlink output power of the amplifier. The amplifier's gain–a measure of its amplification–matters less.

A note on antenna choice: you can likely get away with using an omni-directional outdoor antenna. This makes installation easier as you don’t have to worry about pointing the antenna in the direction of nearby towers.

For smaller homes and apartments (under 1,500 square feet):

Our top choice for smaller homes is the SureCall Fusion4Home. While the power output is relatively low, this is a cost-effective system that can cover up to 1,500 square feet with strong signal outside. We recommend purchasing the version that includes a yagi outdoor and a panel indoor antenna. The performance of the panel antenna is significantly better than the whip antenna and worth the extra money.

For larger homes and offices (over 1,500 square feet):

For larger homes and offices, we recommend using either the HiBoost Home 15K or the Wilson Pro 70 Plus. While the HiBoost brand is not as widely-known, we’ve extensively tested these devices and found them to be on par with other major brands. If you don’t mind using a lesser-known brand with slightly less nice packaging, you can save a significant amount on the total system cost by choosing the HiBoost system. Both of these units have around 10 dBm downlink power, and can cover up to 4,000 square feet when used with with 4 indoor antennas .

The Best Signal Boosters For Larger Buildings (over 5,000 sq ft)

If you’re covering a larger building, we strongly recommend reaching out to our team of signal experts.

Installing signal boosters in larger buildings requires more careful consideration of the environment and outdoor signal levels, and you can save a significant amount on the total system cost by using couplers/taps to daisy-chain antennas. However, designing a daisy-chained system requires careful link budget calculations, which is why we recommend reaching out to our engineering team. Once you get in touch, we’ll create a custom design for your building, utilizing the amplifiers and components that meet your coverage and budgetary needs.

That being said, we do have some recommendations on the types of amplifiers that make the most sense in larger buildings. Our top picks include the following:

WilsonPro Enterprise Signal Boosters

The new line of WilsonPro Enterprise Signal Boosters all perform excellently and can be purchased in a variety of formats, including rack-mountable (Wilson Pro 4000R and Wilson Pro 1000R) and wall-mountable (Wilson Pro 4000, Wilson Pro 1000, and Wilson Pro 1050) options.

The WilsonPro line includes 4-port signal boosters (Wilson Pro 4000R and Wilson Pro 4000). These 4-port devices are useful if it makes the most sense to "home-run" the cables back to a single location. The single-port signal boosters (Wilson Pro 1000, Wilson Pro 1000R and Wilson Pro 1050) are best if you’re daisy-chaining antennas.

The Wilson Pro 1050 is the only signal booster kit available from any manufacturer that includes an "in-line amplifier." This allows considerably longer runs to be used between the amplifier and indoor antennas, and is particularly useful when long cable runs are needed and outdoor signal is weak.

SureCall Force5 2.0

The SureCall Force5 2.0 is an excellent booster that achieves between 11 and 14 dBm downlink output power. That's about the same as our favorite Wilson booster, the Wilson Pro 1000. The Force5 2.0 maxes out the gain limits allowed by the FCC for broadband boosters, making it a top choice for enterprise applications.

The Force5 2.0 is the only system we sell that includes both integrated remote monitoring and the ability to manually tune the amplification and output power on each band. To take advantage of the full power of the system, we highly recommend using multiple indoor antennas.

Cel-Fi Quatra

The Cel-Fi Quatra is the newest line of enterprise-grade products we carry. The technology is more advanced than any of the other boosters we sell; the Quatra digitizes cellular signal and distributes it via ethernet (Cat5e or higher) cable. Similar to the Cel-Fi Go X system, the Quatra only supports one carrier at a time. Currently, compatibility is limited to AT&T and Verizon; however, the system offers up to 100 dB gain, making it ideal when donor signal is weak (less than -80 dBm).

A single Quatra "Network Unit" can support up to 4 "Coverage Units" (similar to indoor antennas in other systems), allowing for a coverage area of up to 50,000 square feet per system. Multiple systems can be installed in larger buildings to provide greater coverage area.

The Quatra system also supports Multiple Input, Multiple Output (MIMO) technology, which improves data rates and overall system performance. It also has a robust remote monitoring and alarm system that allows users to monitor overall system health.

Verizon 4G LTE Network Extender for Enterprise

The Verizon 4G LTE Network Extender for Enterprise (Samsung SLS-BLU102) is an enterprise-grade femtocell (a type of small cell) that can improve coverage in an area of up to 75,000 sq ft for up to 200 users.

Instead of amplifying the outdoor signal, the Verizon 4G LTE Network Extender generates a fresh cell phone signal. It creates a secure VPN tunnel back to Verizon's network over a normal Internet connection. Since the unit generates fresh signal, no outdoor coverage is required in order to use this device.

The Verizon 4G LTE Network Extender for Enterprise is an excellent choice if you only need coverage for Verizon. Multiple units can be installed in the same building to expand coverage even farther.

A few caveats though: first, the unit require both a fast Internet connection and a GPS signal to work. Second, the unit only generates LTE signal. Almost every phone sold in the last 3 years supports Voice over LTE (VoLTE), but if users in the building have older phones that doesn’t support VoLTE, they'll only see a boost in data rates and no improvement for calls.

The Best Signal Boosters For Cars and Trucks

Similar to the limits on gain for buildings, the FCC limits the gain of mobile amplifier kits. Multi-carrier mobile boosters are limited to 50 dB gain, and single-carrier mobile signal booster kits are limited to 65 dB gain.

We’ve sold thousands of car and truck signal booster kits, and our main tip is as follows: for best results, you’ll need your phone to be essentially sitting on top of the indoor antenna. We recommend using a Bluetooth headset or your car’s Bluetooth connection for actually making and receiving calls (it’s safer, too!).

Our Top Pick: the weBoost Drive Sleek

The best format for a car or truck booster is a "cradle" type device that encloses your phone in better cell coverage. weBoost have a patent on this type of device, and while cradle boosters are limited to 23 dB gain by the FCC, performance is still considerably higher than other devices simply because of the way the cradle's antenna is kept ultra-close to the signal booster.

The brand new weBoost Drive Sleek 470135 is weBoost's latest cradle device. It's beautifully designed, with a number of aesthetic and functionality upgrades that make it our favorite car and truck booster. Due to the format, the Drive Sleek only works with one device at a time, and won't work with tablets or mobile hotspots–our wireless choices below are better if you the Drive Sleek isn't an option.

A separate version, the weBoost Drive Sleek 470135F, is designed for Canadian users only.

A Wireless Signal Booster Option for Cars & Trucks

The Cel-Fi GO M isn't cheap at $600. And, like other Cel-Fi devices, the GO M only works with one carrier at a time, and only supports AT&T, Verizon and T-Mobile – it can't be used with Sprint or any Canadian carriers.

However, if you want the absolute best wireless in-vehicle booster, the GO M is that. Since it's a single-carrier device, FCC regulations allow it to have up to 65 dB of gain. As a reuslt, the GO M will improve signal even in remote areas with little coverage.

As with all the mobile kits, we recommend placing the in-vehicle antenna directly next to your phone. While it's not quite as convenient as a cradle-format, this will still get you the best coverage.

The Cel-Fi GO M utilizes the exact same amplifier unit as the Cel-Fi Go X, and you can actually switch the GO M into "stationary mode" and use the full 100 dB of gain inside a home, making this unit extremely versatile.

A Second Wireless Signal Booster That Supports All Carriers, Including Sprint

The weBoost Drive 4G-X is our favorite "broadband" wireless signal booster for vehicles. The booster will amplify cell signal by 50 dB, which is lower than the Cel-Fi Go X, but the maximum allowed by law for multi-carrier in-vehicle units. Since it's a broadband booster, the Drive 4G-X will amplify signal for all major US and Canadian carriers. Again, for best performance we recommend putting the in-vehicle antenna directly behind your phone.

The Best Signal Boosters for RVs

Losing connectivity on the road makes long RV trips less fun – and arriving at a camp and finding you don’t have cell signal can be frustrating. Our founder was an RV owner for many years, so we learned a thing or two about which units work best while on the road.

RV signal boosters are categorized by the FCC as “mobile boosters,” which means multi-carrier, "broadband" amplifiers are limited to at most 50 dB in gain. This makes it difficult to cover the entire cabin of your RV with strong cellular signal while on the road. Instead, we recommend keeping the cell booster’s indoor antenna directly next to either your phone or a hotspot device, and then using WiFi and Bluetooth to connect through that device for Internet access and voice calls.

Our Top Pick: the Best Signal Booster for Most RV Owners

Our top recommendation for RV users is the Drive 4G-X OTR. It’s a great system that has been deployed by hundreds of customers for use in RVs. The 4G-X comes in 3 kit variations: the 4G-X, 4G-X OTR, and the newest model, the 4G-X RV. While the 4G-X RV is designed specifically for RV use, its clunky setup actually makes it harder to install and use than the 4G-X OTR. And it’s not just us–the great folks over at RVMobileInternet.com perform thorough field tests and reviews of every RV booster consistently rate the Drive 4G-X OTR as their top choice.

The Best RV Signal Booster for Stationary Use Only

If you spend most of your time stationary at camp sites instead of on the road, you can install a booster designed for homes in place of a mobile booster. These systems are allowed more gain by the FCC - between 65dB and 72dB (depending on the frequency). We particularly recommend the SureCall Fusion4Home with an omni outdoor and indoor whip antenna. While a yagi antenna would provide better performance, trying to figure out the direction every time you arrive at a camp site would likely be a pain.

The Signal Guide: Essential Reading

Like any technology, cell phone signal boosters can be quite complicated. Our goal in this section of the guide is help explain some of the key information about how signal boosters work, how to pick the right accessories, and how to install your signal booster to get the absolute best performance.

We’ll start with the basics, but as you read on, we'll get into more of the details of how to pick out the right booster and install it correctly.

Contents:

  1. 2G, 3G, 4G LTE (and 5G?)
  2. Voice over LTE (VoLTE)
  3. Understanding Bars: They Aren’t Just Signal Strength
  4. Understanding Bars: Causes of Weak and Noisy Signal
  5. Cellular Frequency Bands
  6. How a Cell Phone Signal Booster Works
  7. Measuring Signal Strength and Signal Quality
  8. Amplifier Specs: Gain and Downlink Power
  9. The FCC’s Signal Booster Regulations
  10. In-building Boosters: Choosing an Outdoor Donor Antenna
  11. In-building Boosters: How Many Indoor Antennas to Purchase
  12. In-building Boosters: Which Type of Indoor Antenna to Use
  13. This guide is too long, can you summarize it for me?
  14. Signal Booster Terminology

1 2G, 3G, 4G LTE (and 5G?)

2G, 3G, 4G LTE Signal Booster, and 5G Signal Boosters

Cell phone technology is typically released in generations; 2G, 3G, and 4G all refer to cellular technologies released over the past 30 years. While it used to be the case that 4G LTE was used for only data, increasingly carriers are using 4G LTE for both voice and data service. Here’s a quick rundown of each technology:

  • 2G: 2nd generation cellular networks were released starting in the early 1990s. There are two types of 2G technology: CDMA and GSM. Verizon and Sprint both chose to use CDMA technology, while AT&T and T-Mobile chose to use GSM technology. 2G supports only very minimal data transmissions.
  • 3G: 3rd generation cell technology was rolled out by carriers starting in 1998. Again, there are two types of 3G technology: CDMA200 (and EVDO), and UMTS/WCDMA/HSPA. Again, Verizon and Sprint chose to use CDMA2000/EVDO technology, while AT&T and T-Mobile chose to use UMTS/WCDMA/HSPA technology.
  • 4G: When the 4th generation of cellular networks rolled out, carriers unified around a single technology: LTE. LTE allows considerably faster connection speeds, and was initially used only for data service, with older 2G and 3G technologies being used for voice. In the last few years, 4G LTE has started becoming the predominant technology for voice as well as data.
  • 5G: The specifications for 5G are yet to be finalized, so no one knows exactly what the technology will entail. However, it’s looking likely that 5G will include “millimeter wave” signals at higher frequencies, and even faster data rates.

2 Voice over LTE (VoLTE)

VoLTE: Voice over LTE Signal Boosters

In the last three years, carriers have begun rolling out “Voice over LTE” technology. This allows phones to make calls entirely over the 4G LTE network, without ever connecting on the older 2G and 3G networks. Different carriers are at different stages of this roll-out:

  • AT&T has rolled out Voice over LTE across the country. Any device released in the last 3 years (e.g. iPhone 6 and above) will make calls over LTE when signal is available. AT&T has also now shut down their 2G GSM network, and is only running a 3G and 4G LTE network.
  • Verizon has also rolled out Voice over LTE across the country. Any device released in the last 3 years (e.g. iPhone 6 and above) will make calls over LTE when signal is available. Verizon plans to shut down their 2G network in 2019.
  • Sprint has not rolled out Voice over LTE, and currently relies on their 3G CDMA2000 network for calls.
  • T-Mobile was the first to roll out Voice over LTE across the country. Any device released in the last 3 years (e.g. iPhone 6 and above) will make calls over LTE when signal is available.

3 Understanding Bars: They Aren’t Just Signal Strength

Signal Strength and Signal Quality can both cause low bars

Most people think the bars on their phone represent signal strength. But that’s not actually the case - signal bars are showing you two things:

  • Signal strength: A measure of the strength of the cellular signal when it reaches your phone (measured in dBm)
  • Signal quality: The ratio of actual source signal to the noise and interference also received by your phone (measured in dB)

Signal quality can limit the number of bars just as much as signal strength. Understanding this fact is really important for installing a signal booster correctly.

As we mentioned above, most cell networks utilize LTE for both calls and data transmissions. In LTE networks, signal strength and signal quality are typically called "RSRP" and "SINR."

  • Reference Signal Received Power (RSRP): RSRP is a measure of an LTE signal's strength. Strong signal is around -70 dBm RSRP, while weak signal is around -100 dBm RSRP.
  • Signal to Interference Plus Noise Ratio (SINR): SINR is a measure of an LTE signal's quality. Clear signal has a SINR of over 10 dB, while low quality signal has a SINR of under 5 dB.

We'll show you how to measure each of these in the Measuring Signal Strength and Signal Quality section below.

4 Understanding Bars: Causes of Weak and Noisy Signal

There are four things that can cause you to see fewer bars and experience dropped calls and lower data rates. Often it’s not just one of these factors but a combination that causes weak reception at any particular location.

1 – Inter-cell Interference

Modern cellular technologies such as 4G LTE use the same frequency bands to transmit signal from all towers. If your phone is located between two or more towers of roughly equal signal strength, the other signal towers will act as “interferers” to the tower you’re trying to connect to, causing lower signal quality (in LTE, this is measured as RSRQ and SINR). Inter-tower interference is one of the main common reasons we see weak signal in urban and suburban areas.

2 – Distance from the nearest cell phone tower

Cellular signal is weakened as it travels through space. If you’re very far away from the nearest cell phone tower, your signal will likely be quite weak. The cell phone’s internal radio will have a hard time “hearing” the cell tower’s signal (the “downlink” signal), and similarly, the cell tower will have a hard time “hearing” your cell phone (the “uplink” signal).

3 – Building materials/vehicle construction

Even if the signal outside the building or vehicle is strong, materials like drywall, wood, concrete, metal, and low-e glass can attenuate the signal, making it weaker inside a home, office, and vehicles.

4 – Geography and nearby buildings

In the same way that building materials block signal, your signal reception can be limited by attenuation from buildings between you and the nearest cell tower. The natural geography plays a part too: signal often can’t be received in valleys or behind hills and mountains.

A signal booster can help no matter which of these is causing poor cell reception. But in each case, there are slightly different nuances to ensuring you pick the right equipment.

5 Cellular Frequency Bands

Cellular service runs on a number of different bands that are licensed to the carriers by the Federal Communications Commission (FCC). There are 4 main frequency bands used by carriers in the US. These four bands are supported by almost all of the boosters we sell:

  • 700 MHz band (LTE band numbers 12, 13, and 17): Used by AT&T, Verizon, and T-Mobile for 4G LTE service only.
  • 850 MHz “Cellular Band” (LTE band 5): LTE band numbers used by AT&T and Verizon only, mostly for 2G and 3G service, though both are beginning to transition to LTE on this band.
  • 1900 MHz “PCS Band” (LTE band 2): Used by all four major carriers for a mix of 2G, 3G, and 4G LTE service.
  • 2100 MHz “AWS Band” (LTE band 4): Used by T-Mobile, AT&T and Verizon for 4G LTE service only.

There are three more bands that are used more selectively, and aren’t amplified by most broadband signal boosters:

  • 850MHz extension band (LTE band 26): Used by Sprint only.
  • 2300 MHz (LTE Band 30): Used by AT&T in some areas only.
  • 2500 MHz (LTE Band 41): Used by Sprint for LTE service only.

No carrier uses just one frequency band in any particular area. Your phone will automatically switch between the different bands depending on which band offers the clearest and strongest signal.

The most important thing to know about frequency is that the higher the frequency, the more easily the signal is attenuated . So, for example, a 2500 MHz signal has a much harder time penetrating a building than a 700 MHz signal. However, it’s worth noting that higher frequencies are able to transfer more data.

How does this affect a booster installation? Even after you install a signal booster, the higher frequencies will still be attenuated more easily. As a result, boosting signal on the 700 MHz band inside a building is typically easier than boosting signal on a higher frequency band.

6 How a Cell Phone Signal Booster Works

How a Cell Phone Signal Booster Works

A signal booster works by amplifying the cell phone signal being sent to and from your phone to the nearby tower. There are three main components:

  • Donor antenna: The donor antenna is installed on the roof, and sends and receives signal from the tower. For some buildings, it makes sense to use a directional antenna. Using a directional antenna lets you aim at a particular tower, which both makes that signal stronger and reduces inter-cell interference.
  • Amplifier: The amplifier, sometimes called a “Bi-Directional Amplifier” (BDA) or booster, amplifies both signals coming from the tower to your cell phone and signal going back to the tower. The amplifier is connected to the donor antenna and indoor antennas by coaxial cable.
  • Indoor antenna(s): The indoor antennas distribute signal to, and receive signal from, your cell phone. The two most common types of indoor antenna are panel antennas and dome antennas.

7 Measuring Signal Strength and Signal Quality

As we explained in the Understanding Bars section, signal strength and signal quality both impact the number of bars you see on your phone. Here’s how you can measure each:

LTE Signal Strength (RSRP):

  • On Android phones, download the LTE Discovery app. The signal strength, in dBm, is shown at the top left of the "Signals" tab.
  • On iPhones, you will need to access “Field Test Mode” to see your signal strength. On some newer Verizon and Sprint iPhones it isn't currently possible to use Field Test Mode to get a signal strenght measurement. Check out our guide to the iPhone Field Test Mode for more information–you may need to find an Android phone for testing if your phone doesn't support signal strength measurements.

LTE Signal Quality (SINR):

  • Signal quality information is harder to access on some phones.

  • On Android phones: on some models the same LTE Discovery app will show signal quality. Long press on the signal bars in the top left of the "Signals" tab. This will bring up a menu that contains an option to enable SINR.
  • On iPhones, you’ll again need to access your iPhone's Field Test Mode to find this information. Again, SINR is not shown on some newer Verizon and Sprint iPhones.

8 Amplifier Specs: Gain and Downlink Power

The two main specifications of an amplifier that we think you should pay attention to are “gain” and “downlink power.” Here’s a little more on each:

  • Gain is a measure of how much the signal is amplified, measured in dB. The larger the gain value, the more the signal from the donor antenna is amplified.
  • Downlink output power, measured in dBm, is the maximum signal that the amplifier can retransmit inside the building or vehicle. The maximum downlink output power sets the maximum coverage area of the system when the amplifier has enough signal.

Each of these specifications is important, but in different situations:

  • If you have weak outdoor signal (-80 dBm RSRP or less) your amplifier will be gain-constrained: If signal at the donor antenna location (on top of your building or outside your vehicle) is quite weak (less than -80 dBm RSRP), the most important factor is the gain of the amplifier. Even with all the gain of the amplifier, you’re not likely to reach its maximum downlink output power. Since the downlink output power limit will never be reached, thus getting the amplifier with the highest gain possible should be your main goal.
  • If you have strong outdoor signal (-70 dBm RSRP or higher) your amplifier will be downlink power-constrained: If signal at the donor antenna location signal is strong, the most important specification is the downlink output power. In this situation you’re quite likely to hit the maximum output power of the amplifier, so focusing on the downlink output power specification of the booster is the most important factor.

9 The FCC’s Signal Booster Regulations

The Federal Communications Commission (FCC) is the organization that regulates the use of cellular frequencies in the United States. In 2014, the FCC created new regulations that apply to all signal boosters sold in the US. The FCC created two sets of regulations: one set for “broadband” devices that amplify all cellular signals from all carriers, and another set for “carrier-specific” boosters that only amplify the signal of one carrier at a time.

“Broadband” booster regulations:

  • The gain of the amplifier can be no more than: 64 dB for the 700 MHz band, 65 dB for the 850MHz band.
  • The downlink output power of the entire amplifier system, including the losses from the cable, can be no more than 12 dBm.

“Carrier-specific” booster regulations:

  • The gain of the amplifier can be no more than 100dB on any band.
  • The downlink output power of the entire amplifier system, including the losses from the cable, can be no more than 12 dBm per 5 Mhz block.

Since the gain of broadband boosters is limited by the FCC, we recommend using a carrier-specific booster where possible if you have weak signal at the outdoor donor antenna location. At the moment, the only carrier-specific boosters are the Cel-Fi GO X and GO M units, which work with AT&T and Verizon.

10 In-building Boosters: Choosing an Outdoor Donor Antenna

Choosing the right outdoor antenna and aiming it correctly is one of the main ways that you can improve the performance of your signal booster. There are two ways that the right donor antenna can help:

  • Most donor antennas have some gain (measured in dBi). The antenna gain adds to the overall gain of the signal booster system you install. If you have weak outdoor signal, a high-gain outdoor antenna can increase the downlink output power of the system and increase your indoor coverage area.
  • Some donor antennas are directional. This allows you to focus in one direction and improve the clarity of the signal being received by the signal booster system. This helps improve coverage and the number of bars you see.

Omni-directional Antennas

Omni” antennas, as they’re often called, work best when you have strong and clear outdoor signal. They’re considerably simpler to install than directional antennas, as they don’t need to be aimed, but you should make sure you have 3 or more bars of signal where you’re installing the omni antenna.

Directional Antennas

While directional antennas take a little more work to aim and install, we generally recommend them to anyone who has either weaker outdoor signal or in cases where signal is strong but noisy (low SINR and RSRQ).

Aiming a directional antenna takes a little bit of effort, but the benefits are threefold:

  • The antenna’s gain adds to your signal booster’s gain – if signal is weak outside, you can get up to 12 dB extra signal by using a highly directional antenna.
  • If the outdoor signal is noisy, it’s typically due to inter-cell interference – there are multiple nearby towers broadcasting on the same frequencies. A directional antenna lets you focus on one of the towers, and improve indoor coverage.
  • In some cases a broadband, multi-carrier booster’s performance can be affected by a “near-far effect,” where a nearby tower’s signal saturates the amplifier and prevents a weaker carrier’s signal from being amplified. A directional antenna allows you to focus the amplifier on a more distant tower and better balance the incoming signal.

Some people worry that installing and aiming a directional antenna means that you improve signal for one carrier while sacrificing signal on other carriers. However, this only very rarely happens: cell towers are usually clustered in one area (or even on the same pole), and generally the same direction is best for all carriers. And using a directional antenna doesn’t mean that you don’t pick up signal from other directions: just slightly less. You can still get great coverage from two towers on different carriers that are in opposite directions when using a directional antenna – one of those signals will usually be somewhat stronger, and using a directional antenna allows you to aim and equalize the signal coming from each.

How to Aim a Directional Antenna

Aiming a directional for most broadband, multi-carrier boosters requires two people: one person on the roof aiming the antenna, and another person standing indoors, near the signal booster’s antenna, taking signal measurements with each new location and direction. While it’s a little time-consuming, finding the right antenna location and direction can have a huge effect on your signal booster’s performance.

Cel-Fi’s line of products, including the Quatra and GO X, make aiming a directional antenna relatively painless. The devices will give you a signal reading that includes both RSRP (signal strength) and SINR (signal clarity), making it easier to try different antenna locations and directions and find the best signal.

11 In-building Boosters: How Many Indoor Antennas to Purchase

Many of our in-building signal boosters come with options that include multiple additional antennas. So, how many antennas do you actually need? The answer’s a little complicated, but, generally: the more antennas you use, the better. Signal travels much more easily through coaxial cable than it does through air or through walls and doors. By distributing the signal throughout the building via coaxial cable, you’ll see much more consistent coverage.

Now, obviously you don’t want to be installing hundreds of antennas – at some point the number of antennas becomes unaffordable. As a rough rule, we recommend installing one antenna per 1,000 square feet of coverage for home and small office applications.

A more accurate answer needs to take into account the signal strength and clarity at the donor antenna location, the amplifier you’re using, and whether the space you’re covering is large and open or divided by walls. Generally, if your outdoor signal is weak or you’re using a weaker amplifier, you should use more antennas. If the space is more open and there are fewer walls, you can use fewer antennas.

12 In-building Boosters: Which Type of Indoor Antenna to Use

There are two main types of indoor antennas: dome antennas and panel antennas. Many of our kits are available with the option to choose which you want.

Dome antennas

You should use dome antennas when:

  • The area you are looking to cover is not thin and narrow (e.g. a hallway).
  • You are able to access the space behind the ceiling.

Since the cable for a dome antenna emerges from the back of the device, you need to have access to the area above where you’re installing a dome. For example, if you’re installing in an office space with removable ceiling tiles, dome antennas are the way to go. Similarly, if you’re installing in the top floor of a house with an accessible crawl space or attic above, dome antennas can easily be installed.

Dome antennas distribute signal equally in all directions, and should be installed centrally to the area you’re looking to cover. If the space is long and narrow, then a panel antenna may be a better choice

Panel antennas

You should use panel antennas when:

  • The area you are looking to cover is long and thin.
  • You are not able to access to the space behind the ceiling.

Panel antennas are typically mounted on walls. The coaxial cable pigtail usually comes out of the bottom of the antenna, meaning that you don’t need to make a hole in your wall to install the antenna and connect a cable. For that reason, we recommend using panels when you’re not able to access the space behind the ceiling.

Panel antennas focus signal in a beam. Typically the beam is relatively wide (around 45 degrees), but some specialty antennas are narrower. The generally beam-forming nature of panel antennas makes them ideal when you’re trying to cover a long and thin area.

13 This Guide is Too Long, Can You Summarize It For Me?

Sure :)

  • If you need help, pick up the phone and call us. We'll help you get a kit customized for your application. Our phone number is 1-800-761-3041 and we're available from 7:30AM to 4:30PM PST, Mon-Fri.
  • Most calls (except on Sprint) are now made over LTE rather than over 2G or 3G. You should buy a booster that supports 4G LTE. More here.
  • The signal bars you see in the corner of your phone aren't just showing the signal strength: they're also showing the signal quality. Before buying a booster, you should figure out what the signal strength (RSRP) and signal quality (SINR) values are on your roof. More here.
  • Each carrier uses a combination of bands in different areas. Lower frequency bands (700 MHz and 850 MHz) penetrate buildings more easily, so we recommend focusing on amplifying them. More here.
  • The two most important specs to look at for a booster are gain and downlink output power.
    • You should focus on the gain specification if your outdoor signal is very weak (less than -80 dBm).
    • You should focus on the downlink output power specification if outdoor signal is strong (higher than -70 dBm).
  • The FCC sets limits for the allowed downlink output power and gain for signal boosters.
    • The maximum gain for "broadband," multi-carrier boosters (products from Wilson, weBoost, SureCall, etc.) is 64 dB to 72 dB (depending on the frequency) for stationary or in-building use, and 50 dB for mobile or in-vehicle use.
    • The maximum gain for "single-carrier" boosters (products from Cel-Fi) is 100 dB for stationary or in-building use, and 65 dB for mobile or in-vehicle use.
  • If you have weak outdoor signal (less than -80 dBm), you should use a single-carrier booster from Cel-Fi if one is available.
  • If your outdoor signal is strong (higher than -70 dBm), a "broadband" multi-carrier booster from Wilson, weBoost, or SureCall is a better choice.
  • Outdoor antennas (for buildings):
    • If signal on the roof is both strong and high quality (you should see three or more bars) on all the carriers you want to boost, an "omni-directional antenna" should be just fine.
    • If signal is weak or low quality, a "directional" antenna like a yagi or a log-periodic antenna is best. They're a little more complicated to install, but worth the effort.
  • Indoor antennas (for buildings):
    • If signal outside is good, you should install about 1 antenna per 1,000 square feet of coverage. If you have multiple floors, make sure each floorhas its own antennas.
    • Panel vs. Dome antennas: A panel antenna can be installed on walls. Dome antennas must be installed on ceilings. If you have ceiling tiles or crawl-space, you can use dome antennas. Otherwise, use panel antennas.

14 Signal Booster Terminology

  • Radio frequency (RF) – Radio frequency is any frequency used to transmit a wireless radio signal, which includes cellular signal, WiFi signal, and regular FM and AM radio.
  • Downlink signal – the signal sent from the cell phone tower to your phone.
  • Uplink signal – the signal sent from your cell phone back to the tower.
  • The FCC – The Federal Communications Commission, the government organization responsible for regulating use of the airwaves (and signal boosters) in the US.
  • Gain (dB) – Gain is the measure of amplification. The higher the gain, the more the signal is amplified. Gain is typically a positive dB number, and it’s measured on a logarithmic scale. 0 dB gain means no gain. 10 dB gain equates to 10 times the signal strength, but 20 dB gain is 100 times more signal, and 30 dB gain is 1,000 times more signal.
  • Antenna gain (dBi) – Antennas also have gain, but they don’t “amplify” signal. Instead, they focus on sending and receiving signal in a particular direction. dBi is also a logarithmic scale. An antenna with 0 dBi signal doesn’t focus the signal at all, whereas an antenna with 10 dBi signal receives and transmits 10 times more signal from a particular direction than other directions.
  • Attenuation (dB) – Attenuation is the weakening of signal over distance, or as it passes through building material. Attenuation is measured in dB, and is typically a negative value (signal gets weaker). -10 dB attenuation is 10 times weaker signal. -20 dB attenuation is 100 times weaker signal.
  • 3 dB – As mentioned above, dB is a logarithmic scale, and 3 dB is exactly half the power. Most splitters have around 3 dB attenuation – they split the power coming through a coaxial cable in half.
  • Signal strength (dBm) – A wireless signal’s strength is measured in dBm. Similar to gain, the signal is logarithmic. 0 dBm is 1 milliwatt, or 0.001 Watts; 30 dBm is 1 Watt; -10dBm is 0.0001 W, or 0.1 milliwatt.
  • Coaxial cable – Coaxial cable is a special type of cable designed to carry radio frequency (RF) signal. It typically has a copper center conductor, some sort of shielding, and an outer conductor.
  • Donor antenna – The donor antenna in a signal booster system is the antenna typically placed outside the building or vehicle and that communicates with the cell phone tower.
  • Indoor antenna – The indoor antenna in a signal booster system is the antenna that is installed inside the building or vehicle and that communicates with your cell phone.
  • Omni-directional antenna – An omni-directional antenna is an antenna with low antenna gain that receives and transmits signal in almost all directions equally.
  • Directional antenna – A directional antenna is an antenna with more gain, and that focuses receiving and receiving antenna in a particular direction. The three main types of directional antenna are “panel,” “yagi,” and “log periodic” antennas.
  • Dome antenna – A dome antenna is a type of indoor antenna that is typically installed in the ceiling of a building, and transmit signals downwards.
  • Panel antenna – A panel antenna is a type of antenna that can be installed as a donor antenna outdoors or indoors on a wall, and transmits signal outwards in the direction it is facing.
  • Lightning surge protector – A device that protects your home and signal boosting equipment in case lightning hits the donor antenna.