Technical Signal Booster Stuff You Should Know

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What is linearity, VSWR, M2M, where do FCC regulations stand, what is attenuation? Get all this and more in this post.


What is Linearity?

Linearity is the behavior of a circuit, particularly a signal booster, in which the output signal strength varies in direct proportion to the input signal strength. A linear designed signal booster amplifier moves signals in a highly direct way. Nonlinear signal boosters can create problems for the cellular tower by sending feedback to the tower, which impacts the tower’s effectiveness.

Why is linearity beneficial to the resulting cell signal?

A linear cell phone signal booster eliminates what is called ripple, or disturbances, in the band. These disturbances are caused by two cell signal types interfering with one another, which causes inefficiencies in the way the signal moves through space. The result is a lower level of performance from the booster.

Independent linearity is probably the most commonly-used definition of linearity. Independent linearity is defined as the maximum deviation of actual performance relative to a straight line, located such that it minimizes the maximum deviation. In that case, there are no constraints placed upon the positioning of the straight line and it may be wherever necessary to minimize the deviations between it and the device’s actual performance characteristic.

Many times a device’s specifications will simply refer to linearity with no other explanation as to which type of linearity is intended. In cases where a specification is expressed simply as linearity, it is assumed to imply independent linearity.



What is VSWR?

SWR is used as a measurement of efficiency for transmission lines, electrical cables that conduct radio frequency signals, used for purposes such as connecting radio transmitters and receivers with their antennas.

VSWR refers to how efficiently radio-frequency power (RF) is transmitted from a power source (Related Video: What Are Cell Phone Radio Frequencies). In an ideal system, 100% of the energy would be transmitted. However, in order for this to occur the source impedance, the characteristic impedance of the transmission line and its connectors, and the load’s impedance must all be equal.

In the real world, this is not always possible. When there is a mismatch such as the load impedance not matching the transmission line, then there is a fraction of that power that cannot be transferred. Since power cannot disappear, the power that is unable to be transferred travels back along the transmission line toward the source.

Standing Wave Ratio (SWR) is the ratio of the amplitude of a partial standing wave at an antinode (maximum) to the amplitude at an adjacent node (minimum) in an electrical transmission line. The SWR is usually defined as a voltage ratio called the VSWR, (sometimes pronounced “viswar”), for voltage standing wave ratio.

For example, the VSWR value 1.2:1 denotes a maximum standing wave amplitude that is 1.2 times greater than the minimum standing wave value. It is also possible to define the SWR in terms of current, resulting in the ISWR, which has the same numerical value. The power standing wave ratio (PSWR) is defined as the square of the VSWR.

What is M2M?

M2M refers to machine-to-machine communications. It refers to any technology which can transmit an exchange of information between networked devices without the manual assistance of humans.

Examples of M2M communications include ATMs, lotto kiosks, digital billboards or signs, or commercial fleet monitoring. In these instances, information is being sent and received using cellular frequencies.

In order to work effectively, M2M solutions should be sturdy and small-form to fit into any M2M configuration. They should be easy to set up and should be enabled to work with modems, laptops, and other M2M devices.

SureCall cell boosters, antennas, and accessories provide a full range of M2M solutions that provide better data transfer and lower error rates across cellular networks.

Connected to an exterior antenna and M2M modem, SureCall M2M boosters enhance data uploads and downloads while keeping the information encrypted. Combined with SureCall’s industry-leading 3-year warranty and 1% return rate, SureCall provides the ideal solution for enhancing M2M coverage despite remote location or a building’s construction reducing the cell signal.



What does the FCC statement mean to the booster industry?

The 2014 FCC ruling on signal boosters clears many rules and legal barriers surrounding wireless boosters in order to enhance wireless coverage, particularly in rural, underserved, and difficult-to-serve areas, by making it easier for these customers to purchase and implement wireless boosters. It also implements some regulatory framework to ensure these boosters do not adversely affect wireless networks.

With this order, the booster market has increased, especially for larger in-building boosters. In the short-term, the tighter specifications increased the price of boosters. Prices later dropped back to normal rates. The rules, as set by the FCC, are intentionally flexible to encourage further technological advancements (Read: FCC Rules and Standards for Signal Boosters).

Do any boosters currently on the market meet new FCC specifications?

Example: FCC Label for Cell Phone Signal Boosters
Example: FCC Label for Cell Phone Signal Boosters

Yes! All SureCall cell phone signal boosters meet the FCC standards for performance and have the approval of the FCC and North American cell carriers. When reviewing your signal booster options, look for the FCC logo or text (see image). Additionally, any SureCall signal booster we sell in Canada is also ISED approved for use in Canada and Mexico.

There are some signal boosters on the market that are not FCC approved. The risk with purchasing one of these boosters means they can create interference to a wireless network. To eliminate this, the FCC can intervene to request the owner shut down the booster until the problem can be resolved.

Since the March 1, 2014 FCC imposed specifications on signal boosters, manufacturers and retailers cannot legally sell non-conforming signal boosters.

Is the FCC March 1, 2014 deadline still in effect?

Yes, this ruling went into effect on April 20, 2014. Under this ruling, all boosters sold or purchased must meet the FCC network protection standards. The rules are still in effect today.

How can I register a new FCC-approved booster I’ve purchased?

Each network has its own process for registering booster devices.

At what outside temperature range to SureCall signal boosters work?

With their durable metal casings and efficient interior design, SureCall signal boosters work in outside temperature ranges of -4 Fahrenheit to +150 Fahrenheit or -20 Celsius to +70 Celsius.

Does the length of cable between the signal boosters and antennas decrease signal strength?

Yes, cable length does decrease signal strength. Typically, for every 100 ft. of cable signal strength decreases by 3-4dB on the 800 cellular band and 7dBs on the 1800/1900 PCS band.

As you can see, the higher the frequency, the more the signal decreases. For the Verizon and AT&T 700 LTE bands, it would decrease signal strength 3-4 dB as on the cellular band. For the T-Mobile AWS 4G band, signal strength would decrease similar to the PCS band, 7dB, for every 100 ft. of cable length.

If a long length of cable is needed between a cell amplifier and antenna, in-line boosters with lower signal strength are sometimes used to extend the signal along the cable line.

What is Attenuation?

Attenuation is any reduction in signal strength that occurs while transmitting analog or digital signals over some span of distance. Contrary to what some of us may think, attenuation isn’t always a bad thing. In fact, sometimes it can increase your overall coverage area.

When speaking about signal boosters, attenuation can be created a few different ways.

  • Manual attenuation is attenuation that is caused you have dials on a signal booster that allow you to attenuate each of the cellular bands manually.
  • Automatic attenuation is hardware that is built directly into the booster to automatically attenuate each band based on the incoming signals strength.
  • System attenuation can be created using a signal attenuator to reduce the strength of the incoming signal before it reaches the booster.

Attenuation by Signal Type and Distance (CM400 Cable):

  • 30 MHz =  0.7dB of loss per 100 feet
  • 50 MHz =  0.9dB of loss per 100 feet
  • 150 MHz = 1.5dB of loss per 100 feet
  • 220 MHz = 1.9dB of loss per 100 feet
  • 450 MHz = 2.7dB of loss per 100 feet
  • 900 MHz = 3.9dB of loss per 100 feet
  • 1500 MHz (1.5GHz) = 5.1dB of loss per 100 feet
  • 2400 MHz (2.4GHz) = 6.65dB of loss per 100 feet
  • 5800 MHz (5.8GHz) = 10.8dB of loss per 100 feet

For example, 100 ft. of cable from antenna to amplifier would decrease the 1800/1900 MHz PCS frequency by approx. 7-8dBs and decrease the 800 MHz Cellular frequency by 3-4dB. The same could be said about the 700 LTE frequency.

Once you have confirmed everything is in place, in good shape and the booster is still delivering less than the better signal booster performance you had before, contact one of our technical support experts at 888-465-6283 or

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