Understanding Coaxial Cables - The Complete Guide
What is Coaxial Cable?
Patented in 1880, coaxial cable has been a standard means of delivering high frequency electrical signals over distances with low signal loss. It has many applications, including telephone trunk lines, cable television signals, and cell phone boosters. Cables come in many sizes and lengths, each designed for a specific application.
Coaxial cable has an inner and outer core that share a geometric axis. This prevents electromagnetic interference and enables more reliable data transmission over longer distances.
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How is Coaxial Cable Constructed?
Coaxial cable is constructed from a single copper or copper-coated steel wire as the center core which carries the high frequency signal. This wire is surrounded by a dielectric insulator, often made of plastic, which keeps a constant distance between the center conductor and the next layer. This insulator is wrapped with a metal shield made of woven copper, aluminum or other metal. This cancels outside electromagnetic interference. The final layer is a rubber wrapper that insulates the whole configuration.
Coaxial cable can be used in both indoor and outdoor applications with a few differences. Coax used outdoors requires additional insulation to protect the wires from sun and moisture. Cables rated for outdoor use may run along the outside of your home to a satellite dish or to the cable box on the corner. Whether out in the sun or buried in the earth, the cable needs to be protected enough to provide seamless transmissions.
How Does Coaxial Cable Work?
A coaxial cable carries a signal which goes across the center copper wire as well as the metal shield. Both of these metal conductors generate a magnetic field. The insulators keep the signals from coming in contact with or cancelling out each other. The insulators also protect the signal from outside magnetic fields. As a result, the signal is carried over long distances with little interference or signal loss.
What are the Uses and Applications of Coaxial Cables
Coaxial Cable is used by cable operators, telephone companies and internet providers. If you have cable television, you have a coaxial cable installed in your home. Coaxial cables are also used for connecting VCRs to a television or connecting your television set or digital convertor box to a personal antenna.
Signal Boosters
Wilson Amplifiers is the leading provider of cell phone boosters. A coaxial cable is used to connect to a cell phone booster as well. An antenna is installed on the outside of your house, an amplifier boosts cell phone signal on the inside of your house, a second antenna is installed on the inside of your house. The coaxial cable ties the three devices together. Using this technology, you can boost a weak cellular 3G & 4G signal. It cannot create signal where there was none, nor can it boost a landline wi-fi signal.
Basic RF
RF is Radio Frequency. RF waves are generated when an alternating current goes through a conductive material. Coaxial cable carries radio frequency signals.
Cable internet (copper-based)
Cable internet works off a coaxial cable. The copper-based cable is piped into your house from the cable service provider. You then plug the connector into a router or cable modem, which then is plugged into your television or computer for internet and cable viewing access.
Ham radio
Ham radio is a means for people to communicate over the air waves. Coaxial cable connected to the antenna provide a stronger signal. Ham radios can be set up in the middle of nowhere and do not require the internet or cell phone technology.
How Many Types of Coaxial Cables are There?
There are many different types of coaxial cable. Your application will determine which cable has the best characteristics. Consult with your user’s manual and specs of each type to make the best decision. There are hundreds of cables to choose from to fit every need you have, but here are a few common types.
If you are very calculating specific rates of loss or ohms, please see technical specs for each type.
Coaxial cable size chart
PE = solid polyethylene PF = polyethylene foam Max Attenuation (750 MHz (dB/100 ft)
RG-6/U is a very common type of coaxial cable. It has an impedance of 75 Ohm and is used in a wide variety of residential and commercial applications including cable television.
RG-8 is similar to RG-6, but unable to carry pure video signals. It has an impedance of 50 Ohm and is used in audio control rooms, radio stations or as connections for external radio antennas.
RG-11 is a higher gauge cable used for CATV, HDTV, TV antennas and video distribution. It has an impedance of 75 Ohm and provides 3 GHz frequency.
LMR® is the newer generation of RF coaxial cables. They provide greater flexibility, ease of installation and lower cost. They are used as transmission lines for antennas on missiles, airplanes, ships, satellites and communications.
LMR®200 is an outdoor rated flexible low loss communications coax. It has an impedance of 50 Ohm, and is great for short antenna feeder runs. This also has a feature of low PIM.
LMR®240 is also an outdoor rated flexible low loss communications coax with an impedance of 50 Ohm. It is designed for short feeder runs for a variety of applications including GPS, WLAN, and Mobile Antennas.
LMR®400 is a flexible communications coax with an impedance of 50 Ohm. It is used for jumper assemblies in wireless communications Systems and short antenna feeder runs. If you need a cable that requires periodic or repeated flexing, choose this one. LMR®400 was designed to replace the RG-8 cables.
LMR®600 “Half Inch” is designed for outdoor use as well. It is more flexible that air-dielectric and hardline cables in terms of bending and handling. It also has an impedance of 50 Ohm.
LMR®900/1200/1700 are larger cables designed for medium antenna feeder runs with any application requiring an easily routed, flexible low loss cable.
Other Features of Coaxial Cables
Coaxial Cable Length
Coaxial cable comes in varying lengths. The shorter and thicker the cable is rated will determine the strength of the signal transmitted. It is important to choose the right cable length and thickness. In radio systems, cable length is comparable to the wavelength of the signals transmitted. You can study the math involved in deciding the best cable length to use. Characteristics of the cable, such and outside diameter of the inner conductor, inside diameter of the shield, dielectric contact of the insulator and magnetic permeability of the insulator all affect the quality of the wavelength going through your cable.
Coaxial cables and dBm
dBm stands for the power ratio in decibels (dB) of the power measured to one milliwatt. Used in radio, microwave and fiber optic applications, this is the signal strength. The type of coaxial cable used will determine your signal strength and how many dBm your cable can handle.
Coaxial cables and ohms and impedance
Impedance is the amount of resistance the waves proceeding through the coaxial cable encounters. The lower the impedance, the more easily the waves flow through the cable. Each type cable has an impedance rating. Factors affecting this is the size of the cable and what materials the cable is constructed from. Standard coax impedances are 50-75 ohms. This has been tested as a great balance between power handling a low loss.
Coaxial Cables and PIM
PIM stands for Passive Intermodulation. When you connect two metals, the result is nonlinear elements and a distortion in the signal may occur. As the signal amplitude goes up, the effects will be more significant. This happens often when connecting antennas, cables and connectors. PIM problems occur most often in LTE, HSPA and CDMA cellular networks.
What is a Coaxial Cable Connector?
Connectors are on each end of the cable. They are designed to maintain the integrity of the cable as it passed the signal through to your device. They are usually plated with high-connectivity metals such tarnish-resistant gold or silver. The type of connector you need depends on what you are connecting to and how far from the source of power to the device.
A few general types of connectors include:
SMA stands for Subminiature Version A. This is a minimal connector interface for coaxial cable with a screw-type coupling mechanism. It has an impedance of 50 Ohm and are designed for use from DC (0 Hz) to 18 GHz. Applications include microwave systems, handheld radios and mobile telephone antennas.
F-Type Connector - this is a mid-size connector designed for common use. It is the most widely used connector for residential wiring and is used with cable television, satellite television and cable modems. It is commonly used with RG-6/U Cable.
N-Type Connector – this is a larger connector design to be used with thick, commercial cable.
Connectors are either male or female. Male connectors have threads on the inside of the shell and female connectors have threads on the outside of the shell. Check the plug on your device if it is female, you need a male plug and vice versa.
Putting It Together
RG6 Cables with F-Type Connectors
The RG6 cable is a 75 ohm cable with F-Type connectors. This is the same cable used with many Cable/Satellite TV devices and comes pre-wired in many homes, making it simple to wire and install.
The F-Type connector is a mid-size connector designed for common use. It is the most widely used coaxial connector for residential wiring.
Mainly used for the average home installation that covers 2,500 to 5,000 sq ft. Cable length from 20 to 50 feet. Comes only in white.
These come kitted with the popular weBoost Home MultiRoom and the budget weBoost Home 4G.
RG11 Cables with F-Type Connectors
The RG11 cable is another 75 ohm cable with F-Type connectors. What separates it from the R6 is its range: whereas the R6 tops out at 50 feet, the RG11 ranges from 50 to 100 feet and features lower loss.
These do not come pre-kitted with any of our signal boosters, but are highly recommended if you believe it is likely you will be running over 50 feet of cable to power your booster.
Wilson400 Cables with N-Type Connectors
The Wilson400 cable is an LMR®400 spec cable.
These are 50-ohm, pro-grade coaxial cables designed for large installations from 7,500 to 50,000 square feet. Cable length ranges from 50 to 1000 feet, spooled. Your installer will typically apportion the cable into shorter lengths to cover the range of the installation while maintaining quality signal strength.
This Wilson400 is fitted with an N-Type connector, a large connector designed to be used with thick, commercial cable.
The most popular units that include these cables are the weBoost Connect 4G-X and the WilsonPro line of commercial signal boosters. However, they are compatible with any equipment that uses 50 Ohm cables fitted with N-Connectors.
LMR®600 and LDF4/Al4 RPV-50 “Half Inch” with N-Type Connector
If you need to run cable in excess of 150 feet, your installer may recommend either an LMR®600 or a “half inch” coaxial cable. These are extremely thick cables which are much more industrial than any of the other varieties, and are expensive to boot. An installer will only recommend either of these in rare, specialized situations depending on individual need, but should they do so they will certainly have good cause. These are the best available cables to maintain a quality signal strength on the market.
The difference between an LDF4 and an AI4 RPV-50 is the interior - the LDF4 has a foam covering, and the AI4 RPV-50 has nothing. The difference in function, however, is minimal.
RG58 and RG174 Cables with SMA Connectors
RG58 and RG174 cables are used in vehicle boosters. The difference between the two is the better low-loss quality of the RG58 with cable length up to 20 feet compared to the RG174’s 6 feet. For large vehicles, such as RVs or boats, the RG174 is preferred.
Both are fitted with SMA connectors. These are small, copper connectors used in modems and the like. They are relatively inexpensive, which allow for the cable’s cheaper cost.
The difference between the two is the better low-loss quality of the RG58 with cable length up to 20 ft compared to the RG174's max length of 6 ft.
Compatible with weBoost Drive 4G-M, weBoost Drive Sleek, and the weBoost Drive 4G-S.
Considerations Before You Buy Cables
Before you make your coaxial cable purchase, there are several things to consider. What device are you using? A cell booster might require a different cable than a satellite dish. Check the ohms, impedance and connections.
Next, calculate how far you need to go between your devices or from the source of your power to the device. Refer to the section on cable length. Usually, the shorter distance from your source to your device will produce a crisper signal.
Loss of signal is inevitable when traveling across any distance. A shorter cable will have less loss than a longer cable and a thicker cable will have less loss than a thinner cable, but they will all have some sort of loss. The loss that is acceptable will depend on your devices and your application. To minimize the loss, the source and load impedances must be correct. In order to calculate the amount of loss, use an online calculator on the internet, such as www.qsl.net. Input your line type, line length, frequency, load SWR and power input. The matched loss, SWR loss, total loss and power out will be calculated. There are many calculators online and the formulas available to calculated manually.
We do not endorse this one specifically. QSL Loss Calculator
Signal Loss per 10 Feet
With increasing cable length more signal loss occurs. Signal gain and loss is measured in decibels (dB). And decibels are measured exponentially. A loss of 3 dB means a weakened signal by 2x!
Per the chart, the Wilson400 (and the equally powerful RG11) has the best minimal loss and is almost twice as effective compared to the RG6 for home installations. The only cables mightier are the pricey LG600 and even pricier Half-Inch.
The RG174 should never be installed in any unit that needs more than 6 feet of cable since it does a poor job of carrying signal at 10 feet.
As always, you can convert your cable installation with special cable connectors and adapters. However, to mix and match 50 ohm & 75-ohm cables and systems would lead to further signal loss, so it's best to stay consistent with the same type of relevant 50- or 75-ohm system and cables.
What is the difference between 50- and 75-ohm cables? This analogy might help. Think of signal as a drink and cables as straws. 75-ohm cables are your typical soda straws and 50-ohm cables are those big gulp carnival straws.
Manufacturers of Coaxial Cable
Bolton Technical is a leading provider of coaxial cables, connectors and antennas used in high-end electronics and equipment.
Wilson Amplifiers is the leading provider of cellular boosters. Cell phone boosters amplify 4G, LTE, and 3G for any phone with any carrier for home, office, or vehicle.
We seriously hate dropped calls and poor coverage, so it's our goal in life to totally eliminate spotty signal:
- Free consultation (ask us anything) with our US-based customer support (sales@wilsonamplifiers.com) or call us at 1-800-568-2723.
- Free shipping.
- Better signal or industry-leading 90 money-back guaranteed. No questions asked.
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Ask us anything and we'll be glad to help.
LMR® is registered trademark of Times Microsystems.
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