Recommended Spec for Residential Coaxial Cable

[AntonK]

Hi,

Can anyone recommend the correct coax cable spec for me to use (e.g. RG6, or whatever). I have Xfinity 2000/200, and am looking to replace the cable that comes from my wall jack to my modem.

Thanks for any advice.

Anton

 

[heysoundude]

RG6 is the current standard as I understand it...but it should go all the way from the router to the demarc point that it enters your home, and be properly grounded. just going from the gateway device to the wall isn't doing much.

 

[Analog-1]

Yep RG-6 or RG-6 quad shield although a little stiffer to work with. If you have any RG-59 replace it.

 

[tiddlywink]

RG6. If you are having issues, the coax in the walls, splitters, and/or amps is likely the problem.

I did what heysoundude recommends back when I had cable. Ran a single continuous RG6 line from modem to demarc. Make sure your ISP has properly grounded the demarc; they legally have to do this in USA.

 

[Analog-1]

I did what heysoundude recommends back when I had cable. Ran a single continuous RG6 line from modem to demarc. Make sure your ISP has properly grounded the demarc; they legally have to do this in USA.

Easy if your in your own home. Not likely possible if renting an Apt ext.. Comcast don't care about grounding. In fact running a separate ground rod can make things much worse. All home grounds must be bonded together so it all stays at on potential. If this does not happen it makes things worse.

 

[tiddlywink]

Easy if your in your own home. Not likely possible if renting an Apt ext.. Comcast don't care about grounding. In fact running a separate ground rod can make things much worse. All home grounds must be bonded together so it all stays at on potential. If this does not happen it makes things worse.

Your local government cares via electrical codes and will force Comcast to ground their demarc whether at a house or apartment. If your demarc is not properly grounded or worse not grounded at all, Comcast will be legally on the hook to pay for any devices that were damaged.

I didn't even know this until a surge took out my modem, router, and switch from an ungrounded demarc years ago. Cable ISP was there the next day to install grounding and asked me how much my stuff cost. Told him ($600+) and said I would get a bill credit for that exact amount in two days. Looked it up online and they were so nice because they wanted to avoid the fines.

 

[Analog-1]

Just saying comcast don't ground in every install. I have seen this first hand many times. As i said grounding is more complicated than most understand. A stand alone comcast ground would be worse than no ground, unless they bond it to the house electric ground.

 

[tiddlywink]

They must ground according to NEC 820:

Chapter 8 Communications Systems: Communications Systems, Electrical Code of the Texas SFM | UpCodes

UpCodes offers a consolidated resource of construction and building code grouped by jurisdiction

up.codes

 

[AntonK]

Thank you, everybody, for your input.

 

[sfx2000]

Hi,

Can anyone recommend the correct coax cable spec for me to use (e.g. RG6, or whatever). I have Xfinity 2000/200, and am looking to replace the cable that comes from my wall jack to my modem.

Thanks for any advice.

Anton

For CATV - RG58 is enough - and per spec, it's 50 ohm...

DirecTV uses RG6 - which one would think better, but it's not, it's a 75 ohm platform...

For DOCSIS, CATV, MOCA - RG58 is the right choice here...

 

[sfx2000]

Just saying comcast don't ground in every install. I have seen this first hand many times. As i said grounding is more complicated than most understand. A stand alone comcast ground would be worse than no ground, unless they bond it to the house electric ground.

Not sure where you live, but out here in Cali we have a common ground for the house - at my demarc for House AC service, Telco, Cable - there is a ground lug that is driven literally into the ground for about a meter and a half...

this is code...

All services tie into a copper ground bus, there's even a strap from the Gas Meter - the only things not tied to ground as far as i can tell is water and sewer - which isn't really a problem since GFCI is required for any outlets that are close to water in the house - sometimes at the outlet, but generally at the breaker these days on newer installs.

 

[sfx2000]

Can anyone recommend the correct coax cable spec for me to use (e.g. RG6, or whatever). I have Xfinity 2000/200, and am looking to replace the cable that comes from my wall jack to my modem.

If you had a truck roll in - e.g tech install, you're good to go...

Even if you go from the wall jack to the modem, behind it to the demarc is usually RG58 as I discuss above...

 

[sfx2000]

RG6 is the current standard as I understand it...but it should go all the way from the router to the demarc point that it enters your home, and be properly grounded. just going from the gateway device to the wall isn't doing much.

No, it's not...

• RG6 is 75 Ohm
• RG58 is 50 Ohm

Everything over Coax is Radio, so impedance actually matters for optimal frequency response...

 

[degrub]

No, it's not...

• RG6 is 75 Ohm
• RG58 is 50 Ohm

Everything over Coax is Radio, so impedance actually matters for optimal frequency response...

Not sure that is the situation with CATV, at least in the US. 75 ohm seems to be the most commonly used.

1. Why is 75 Ω cable commonly used for cable TV instead of 50 Ω?The main reason for using 75 Ω cable for cable TV is to reduce signal loss and ensure better signal quality. This is because 75 Ω cable has lower attenuation (signal loss) compared to 50 Ω cable, making it more suitable for long distance transmission of high frequency signals.

2. What is the difference between 75 Ω and 50 Ω cable?The main difference between 75 Ω and 50 Ω cable is the impedance. Impedance is a measure of the opposition to the flow of electrical current in a cable. 75 Ω cable has a higher impedance compared to 50 Ω cable, which means it has lower signal loss and is more suited for high frequency signals.

3. Can 50 Ω cable be used for cable TV?Technically, 50 Ω cable can be used for cable TV. However, it is not the most optimal choice. 50 Ω cable is better suited for lower frequency signals, such as those used in radio communication. For cable TV, 75 Ω cable is the standard and recommended choice for better signal quality.

4. Are there any other advantages of using 75 Ω cable for cable TV?In addition to lower signal loss, 75 Ω cable also has better impedance matching with the equipment used in cable TV systems. This means that the signal can be transmitted more efficiently and with less interference, resulting in better overall picture and sound quality for viewers.

5. Is there a reason why 50 Ω cable is not used for cable TV?As mentioned before, 50 Ω cable is not the most optimal choice for cable TV due to its higher signal loss and lower impedance matching. Additionally, 75 Ω cable has been standardized and widely used in the cable TV industry, making it more accessible and cost-effective compared to 50 Ω cable.

Reference: https://www.physicsforums.com/threa...nly-used-for-cable-tv-instead-of-50-o.837408/

 

[tiddlywink]

Not sure that is the situation with CATV, at least in the US. 75 ohm seems to be the most commonly used.

https://business.comcast.com/~/media/business_comcast_com/PDFs/Re-Arch/2021/FiberToTheBuilding%20Specifications%20051319%201.pdf

Wiring Specifications
Coaxial Cable
All coaxial cable within the property, including the drop cables from the unit to the common distribution
room, shall meet or exceed the following requirements:
• RG-6 Tri-Shield for drop lengths up to 150’.
• RG-11 Tri-Shield for drop lengths between 151’ and 250’.
• Drop lengths should not exceed 250’. Each unit will have its own coaxial cable drop from the nearest
intermediate/main distribution frame terminal/cabinet to the unit with no additional splices/splitters
between the unit and the intermediate/main distribution frame coaxial terminal/cabinet.
• All coaxial cables used for RF signal distribution shall meet the minimum physical and electrical
requirements of ANSI/SCTE 74 2003, Specification for Braided 75 ohm Flexible RF Coaxial Drop Cable,
and must be approved by Comcast Project Coordinator (CPC). Cables used for RF signal distribution
in all new installations must be a minimum size of Series 6 with a minimum foil-braid-foil, Tri-Shield
configuration that includes a bonded inner foil tape, outer foil tape bonded to the jacket and at least
77% braid coverage.
• Alternative coaxial cable or connectorization needed for coaxial shielding termination requires CPC
approval prior to installation

------------