Ultimate Cable Internet Wiring & Optimization Guide (2021)

Learn how to optimally wire your home or office cable Internet.

Coax Equipment: Attenuator, MoCA POE Filter, Grounding Block Kevin Jones / TechReviewer

Last Updated: September 14, 2021

Written by Kevin Jones

During or after reading through this article, you'll likely want to check out these related articles:

Required Components and Connections

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To set up cable Internet, you'll need a cable modem (TR). The modem will connect to a coax cable (TR) provided by your ISP (Internet Service Provider). Your internet service provider may have run coax cable to the outside of your property or wired them up to coax outlets in your office or residence. In either case, you'll need to finish the connection to your modem with RG-6 coax cables. Some ISPs may rent you a modem for a monthly rate, or you can purchase your own.

With a cable modem alone, you could connect a single computer to the Internet. Connecting only one computer would require a single Cat 5e (or higher) Ethernet cable (TR) connecting the computer/device to the modem. Typically, however, you will have more than one device that you'll want to be able to connect, such as a phone or additional computer.

To distribute internet access throughout your home or business, you will additionally need a router (TR), which connects to the modem via a Cat 5e (or higher) Ethernet cable. Some modems have built-in routers, or you can purchase one separately. Most routers currently available come with Wi-Fi capabilities (for connecting devices wirelessly) and ports for computers/devices to connect to via a Cat 5e (or higher) Ethernet cable.

If you are in a large house or building, you have a few options for distributing the Internet throughout the building:

  • Run Ethernet Cable (Cat 5e or higher) throughout the building or use existing coax cabling in the building for Ethernet communication, with MoCA Adapters (TR)
    • You can additionally add Wi-Fi Access Points (TR) to make Wi-Fi available at the ends of the cables.
    • You can additionally add Switches (TR) or Hubs (TR) to make more wired connections available at the ends of the cables (e.g., for a particular room).
  • Use a Wi-Fi Mesh System (TR), which repeats Wi-Fi signals as needed to distribute access.
  • Use a Wi-Fi Repeater/Extender (TR), which repeats Wi-Fi signals from an existing Wi-Fi router.

For more details on these options, check out my Essential Equipment Guide for Cable Internet (TR).

Suppose you have DVRs (devices that can record and play-back TV shows), nearby neighbors, or use MoCA Adapters. In these cases, you'll want to use a POE MoCA Filter (TR). A POE MoCA Filter ensures data privacy by blocking outgoing MoCA signals, improves MoCA signal strength by reflecting the signal, and reduces interference by filtering out data from your neighbor's devices.

If you have TVs that also connect to the coax cable, you'll need coax splitters. In the Optimize the Signal Level (TR) section below, we'll discuss how the usage of splitters reduces signal strength.

As you'll also find out below in the Optimize the Signal Level (TR) section, you may need attenuators, amplifiers, and terminators to get the best signal (power) level and minimize noise (signal-noise ratio).

How to Verify That the Cable Modem Signal Is Good

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The modem's diagnostics page is the best way to verify that you are meeting the recommended signal levels for the cable modem. It also allows you to confirm that you don't have too much noise/interference.

The diagnostics page is typically available on your local network at: http://192.168.100.1/. Check your modem's manual if it is not available at this address.

Your modem diagnostics page may not look the same but should provide similar information.

Keep in mind that these diagnostic values are a snapshot from a single point in time. You usually have to refresh the page to get updated values.

Next, we will look into how to evaluate and improve these numbers.

Upstream Modem Power Levels Upstream Modem Power Levels Kevin Jones / TechReviewer

Downstream Modem Power Levels and SNR Downstream Modem Power Levels and SNR Kevin Jones / TechReviewer

Correctable and Uncorrectable Codewords Correctable and Uncorrectable Codewords Kevin Jones / TechReviewer

What Is Signal Strength / Power Level for a Modem?

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Signal Strength, or Power Level, is the amount of power sent or received by the modem in units of dBmV. The dBmV unit type represents a voltage relative to a reference voltage of 0 dBmV.

Note that 0 dBmV doesn't mean "No Power." You want to get the received (Downstream) power level close to 0 dBmV. A positive value such as +10 dBmV and a negative value such as -10 dBmV are further from the desired reference voltage level.

What Are Acceptable Signal Strength Values?

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DOCSIS 3.0 / 3.1 Cable Modem - Power Levels
RecommendedMinMax
Downstream Power Level -7 dBmV to +7 dBmV -10 dBmV +10 dBmV
Upstream Power Level +35 dBmV to +49 dBmV +35 dBmV +55 dBmB

What Causes Low Input/Downstream Power Levels?

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Low downstream power means that the power level which is reaching your modem is too low. Low downstream power is caused by too many splitters (TR) or attenuators (TR) or too long of a cable run.

You can mitigate low downstream power levels with a coax amplifier.

What Causes High Input/Downstream Power Levels?

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High downstream power levels result from either being close to the ISP's transmitter or using an amplifier (TR).

While inserting a splitter would typically result in about a 3 dB power reduction, it can also increase SNR and require a terminator (TR) for unused ends.

The recommended solution is to use a single attenuator (TR) to reduce the power level.

If you are using an amplifier, you could either remove it or not amplify the coax cable section going to the cable modem.

What Causes High Output/Upstream Power Levels?

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High upstream power means that your modem needs to use a higher signal level to reach the ISP's receiver. High upstream power can be caused by a failing coax splitter (TR) or connectors or too many splitters.

What Is SNR for a Modem?

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SNR stands for Signal to Noise Ratio. SNR is the level of the desired signal relative to the level of background noise. Higher values mean that the signal has low levels of noise.

MER, modulation error ratio, is the measure of SNR for cable modems.

What Are Acceptable SNR Values?

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DOCSIS 3.0 / 3.1 Cable Modem - Signal to Noise Ratio (SNR)
RecommendedMinMax
Downstream Signal to Noise Ratio (SNR) At least 35 dB 30 dB

What Are Correctable and Uncorrectable Codewords?

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Correctable and Uncorrectable Codewords refer to errors in received data.

High uncorrectable codewords quantities are often problematic.

Correctable codewords are not a problem, as it means that the modem could fix the invalid data, making it valid.

Uncorrectable codewords mean that the data was unrecoverable. A few uncorrectable codewords may not be noticed. However, as the error rate increases, you'll see audio in voice communication dropping out, slow page loading, jumping video games. If it gets bad enough, your Internet may not work at all.

Correctable and uncorrectable codewords may be symptoms of incorrect power levels or high noise levels. Keep in mind that even if these levels look good, a periodic spike in noise could cause inconsistent outages.

How Can SNR Be Improved?

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SNR can be improved by:

  • Removing unneeded coax splitters (TR)
  • Terminating or removing unused coax cables and outlets
  • Using quality connectors (F Type RG-6 Compression Connectors)
  • Using quality cables (RG-6 Coax (TR))
  • Removing devices that are causing interference, such as DVR devices, or blocking their signals from reaching the modem by using a MoCA POE Filter / 1 GHz Low-Pass Filter (TR)
  • Reducing propagation of MoCA signals from other homes, with a MoCA POE Filter / 1 GHz Low-Pass Filter

Types of Coax Cables

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75 Ohm RG-6 (TR) is the typical coax cable type you'll find in your home.

The max length of a coax run depends on the transmit power of your modem and your ISP's transmitter.

For every 100 meters (328 feet) of RG-6, there will be 2.3dB of attenuation (signal loss) for the lower frequencies.

RG-11 is thicker and can be used for longer runs. It gets 1.2dB of attenuation per 100 meters (328 feet).

You can mitigate longer runs with a coax amplifier (TR), which increases the signal level.

Find RG-6 Coax Cables on Amazon (affiliate link).

Find RG-11 Coax Cables on Amazon (affiliate link).

Types of Ethernet Cables

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Ethernet cables (TR), the wires used for connecting most home and office networking equipment, all use the same connector type, RJ-45. However, there are many types of Ethernet cables to consider: Cat 5e, Cat 6, Cat 6a, Cat 8. They have progressed over time to support increased speeds while thankfully remaining backward compatible. The most commonly used Ethernet cable is currently Cat 5e.

The speed you'll reach depends on the cable type and support by your network devices.

Cat 6a is my recommendation for new in-wall installations and future-proofing, as it's fast but less flexible than Cat 5e. Find Cat 6a Cables on Amazon (affiliate link).

Tripp Lite Cat6a Cable 10G-Certified Tripp Lite Cat6a Cable 10G-Certified Check Price on Amazon (affiliate link)

Cat 5e is my recommendation for in-room usage due to its increased flexibility. However, if you want to reach speeds over 1 Gbps, stick with Cat 6a and up. Find Cat 5e Cables on Amazon (affiliate link).

Cat 7 isn't very popular due to its use of an uncommon GG45 connector; other Ethernet cable categories use an RJ-45 connector. Additionally, it never gained much market traction. If you see something marketed as Cat 7 but has an RJ-45 connector, then it's not Cat 7 cable. Your best bet is to avoid Cat 7, as it will likely not be worth the extra expense.

Cat 8 is more expensive than Cat 6a. Assuming you won't be reaching speeds over 10 Gbps with your home networking equipment, I'd recommend sticking with Cat 6a over Cat 8. Find Cat 8 Cables on Amazon (affiliate link).

Tripp Lite Cat8 Cable 25G/40G-Certified Tripp Lite Cat8 Cable 25G/40G-Certified Check Price on Amazon (affiliate link)

While not typically considered an Ethernet cable, you can use new or existing coax cables for Ethernet communication using MoCA adapters (TR). MoCA 2.5 adapters allow for speeds of up to 2.5 Gbps.

Ethernet Cable Max Speeds and Distances
Cable CategoryMax Speed and DistanceNotes
Cat 5
  • 100 Mbps @ 100 meters
Cat 5e
  • 1 Gbps @ 100 meters
Recommended for In-Room. More flexible than Cat 6 and up.
Cat 6
  • 10 Gbps @ 55 meters (37 meters if high cross talk)
  • 1 Gbps @ 100 meters
Cat 6a
  • 10 Gbps @ 100 meters
Recommended for In-Wall.
Cat 7
  • 100 Gbps @ 15 meters
  • 40 Gbps @ 50 meters
  • 10 Gbps @ 100 meters
Not recommended or intended for use as a typical Ethernet cable; go with Cat 6a rather than this type. Most home network equipment would run at Cat 6 or Cat 6a speeds. This is also more expensive than Cat 6a.
Cat 8
  • 40 Gbps @ 30 meters
  • 10 Gbps @ 100 meters
More expensive than Cat 6a, which is why I don't recommend these currently. Most home networks don't currently support over 10 Gbps.
Coax (MoCA 2.5)
  • 2.5 Gbps @ 30 meters
Not typically considered an Ethernet cable, but it can allow for Ethernet communication using existing wiring.

Note that your equipment will need to support the appropriate speeds:

Ethernet Port Type Ethernet Cable Needed for Max Speed
Fast Ethernet (10/100) Cat 5
Gigabit Ethernet (10/100/1000) Cat 5e
10 Gigabit Ethernet (10/100/1000/10000) Cat 6a or Cat 8
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Finding Ethernet cables which comply with their category rating can be a little tricky. Some manufacturers use misleading or incorrect naming, and their cables do not allow you to get the maximum expected speeds.

Here are some cables which we recommend:

Optimize the Signal Level

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Here is some additional background knowledge to help you plan your wiring setup.

Splitters

Coax splitters (TR) are used for splitting a coax cable to go to multiple destinations. Two-way passive splitters typically result in 3.5 dB of signal loss per output. Splitters with more ports are often made up of multiple two-way splitters, which results in even higher losses on some ports.

Because each splitter may introduce some amount of noise,

Splitters have a supported frequency range.

For cable modem signals, you'll want a splitter that supports at least up to 1 GHz (1000 MHz).

DOCSIS 3.1 and DOCSIS 4.0 (TR) modems may support frequencies up to 1218 MHz and 1.8 GHz, respectively. As ISPs begin to adopt these frequencies, you may need to upgrade your splitters to ones that support these frequencies.

Suppose you have MoCA devices (TR) communicating over the coax cable, such as DVRs or MoCA Adapters. Those sections will require splitters that support the higher MoCA frequency ranges of up to 1625 MHz.

Find Coax Splitters on Amazon (affiliate link).

Terminators

Unused coax outlets and splitter ports will reflect all power, which propagates backward along the line. Reflections may or may not cause problems, but ideally, all ports and outlets should be terminated.

75 Ohm RG-6 coax cable should be terminated with a 75 Ohm terminator (TR).

Find Coax Terminators on Amazon (affiliate link).

Attenuators

Attenuators (TR) reduce the power level by specified amounts, such as 3 dB or 6dB. These are preferred over using a splitter to reduce power.

Find Coax Attenuators on Amazon (affiliate link).

Amplifiers

While amplifiers (TR) help increase a signal level by a particular amount, they also increase noise by the same amount. For this reason, they should only be used when necessary.

Find Coax Amplifiers on Amazon (affiliate link).

MoCA POE Filters

MoCA Point of Entry Filters (TR) filter out the 1 GHz+ frequencies used by MoCA device communications.

MoCA devices commonly include DVRs and MoCA adapters (TR) and can be used for Ethernet communication over a coax cable.

MoCA POE Filters are beneficial for privacy, to prevent leaking data to your nearby neighbors, as well as reducing noise on the line.

They also reflect the MoCA frequencies, which can be desirable for improved MoCA device communication.

One potential drawback of MoCA POE filters is that they filter out the upper ranges of frequencies supported by DOCSIS 3.1 and 4.0. This filtering may impact maximum speeds or cause connection problems if these frequency ranges are required. However, your ISP may not even use these frequency ranges at this time. Learn more about DOCSIS in our DOCSIS Cable Modem Guide and Version Comparison (TR).

As the Point of Entry aspect of the name implies, MoCA POE Filters are typically placed at the entry point of your residence. However, when your main splitter is inside your residence, it can be beneficial to put the filter at this location. Placing it here can reduce the signal propagation of the reflected signal.

Find MoCA POE Filters on Amazon (affiliate link).

Troubleshooting

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For additional troubleshooting strategies, you can check out my Ultimate Cable Internet Troubleshooting Guide (TR).