The Complete Guide To Understanding Coaxial Cable
- 30 Oct, 2019
What is Coaxial Cable?
Coaxial cable became popular in the 1880’s, invented by english engineer and mathematician Oliver Heaviside. It became the common means to deliver high frequency electrical signal over various distances with low loss. There are thousands of applications for coaxial cable, including satellite television signal, telephone lines and cell phone signal boosters. Coaxial cables come in a variety of sizes and lengths - each useful 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.
How is Coaxial Cable Made?
A. Steel Wire Core
C. Metal Shield
D. Rubber Sheath
Coaxial cable is made from copper or copper-coated steel wire, which is the center core that 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 stops any electromagnetic interference. The final layer is a rubber sheath that insulates the entire cable.
Coaxial cable can be used in both outdoor and indoor settings with a few distinctions. Coax used outdoors requires more insulation to protect the wires from the sun and moisture. Cables approved for outdoor use may run along the outside of your home to a satellite dish or to you Cell phone signal booster’s antenna. Whether out in the sun or buried in the earth, the cable needs to be protected enough to provide consistent, flawless transmissions.
How Does Coaxial Cable Work?
A coaxial cable carries a signal which runs 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 interfering with each other or negating each other. The insulators also protect the signal from outside magnetic fields. As a result, the signal is carried over far distances with little disturbance or signal loss.
Uses and Applications
Coaxial Cable is used by satellite TV installers, telecom companies and internet providers. If you have satellite television, you have a coaxial cable installed in your home. Coaxial cables are also used for connecting a DVD Players or streaming device to a television or connecting your television or digital convertor box to a personal antenna.
Bolton Technical is the leading provider of cell phone signal boosters and accessories in South Africa. 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, which broadcasts amplified signal in your home. The coaxial cable ties the three devices together. Using this technology, you can boost a weak cellular 2G, 3G & 4G signal. It cannot create signal where there was none, nor can it boost a landline wi-fi signal.
RF is Radio Frequency. RF waves are generated when an alternating current goes through a conductive material. Coaxial cable carries radio frequency signals.
Broadband Internet (Copper-Based)
Broadband 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 modem, which then is plugged into your television or computer for internet and Smart TV streaming.
Ham radio or “Amateur radio” is a means for people to communicate over the air waves.These devices are mostly used for non-commercial exchange of messages and are often used for public safety or other professional services such as taxis, aviation or maritime. 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.
Different Cable Types
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.
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
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.
Connectors are on each end of the cable. They are designed to maintain the integrity of the cable as it passes 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 750m2 to 1500m2.
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 15 meters, the RG11 ranges from 15 to 30 meters 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 15 meter of cable to power your booster.
The Bolton400 cable is an LMR400 spec cable.
These are 50-ohm, pro-grade coaxial cables designed for large installations from 2500 to 15 000 square meters. Cable length ranges from 15 to 30 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 Bolton400 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 WilsonPro A500 and WilsonPro A1000 range of signal boosters. However, they are compatible with any equipment that uses 50 Ohm cables fitted with N-Connectors.
If you need to run cable in excess of 45 meters, your installer may recommend either an LMR600 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 cell phone signal boosters for vehicles. The difference between the two is the better low-loss quality of the RG58 with cable length up to 6 meters compared to the RG174’s 1.5 meters. For large vehicles, such as Caravans 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 6 meters compared to the RG174's max length of 1.5 meters.
Compatible with weBoost Drive AM100-Pro.
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 phone signal 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 3 Meters
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 Bolton400 (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 1.8 meter of cable since it does a poor job of carrying signal at 3 meters. 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 Cell phone signal boosters, coaxial cables, connectors and antennas used in high-end electronics and signal boosters. Cell phone boosters amplify 4G LTE, and 3G for any phone with any network 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 local customer support (firstname.lastname@example.org) or call us at +27 11 749 3085.
- Free delivery on orders over R500.
- Better signal or industry-leading 30 money-back guaranteed. No questions asked.
- We want everyone to be satisfied, so we provide lifetime technical support and a 1-year warranty for all products.
Ask us anything and we'll be glad to help.