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2. CATV Wiring

The most common grades of CATV cable used in homes today are RG59 and RG6 (aka RG56).

RG59 was the standard for home wiring many years ago, but is generally problematic today. RG59 is a lower grade of coaxial cable, consisting of a small center conductor, a small insulating dielectric, and typically, a single outer shield.

RG6 is the standard today and has a larger center conductor, a dual or quad shield, and a much larger insulating dielectric, thus ensuring more bandwidth and a lower frequency loss per foot.

RG11 is higher quality than RG6, but also much thicker and harder to work with. It is usually used for longer cable runs (over 150 feet) because it loses signal more slowly. I do not know of any stores that carry RG11/F11 cable.

There are several other grades, but they are uncommon and beyond the scope of this FAQ.

by Raydr See Profile edited by ergibbs See Profile
last modified: 2003-07-10 06:35:29

All conductors lose a certain amount of signal over distance. The "bigger" a conductor is, the less signal is lost over distance (you'll see why this is important later).

Also, dual/quad shield refers to how many layers of "shielding", or layers of "silver metal", cover the dielectric.

The dielectric is next, which is the opaque, white, waxy part of the cable. This is insulation from shielding.

The shielding is the layer of braided wire. The purpose of the shielding is just that. It shields the conductor from stray "outside" signals, also known as ingress (more on ingress later). It also keeps the signal being carried along the conductor INSIDE the cable (prevents egress, which is signal leaking OUT). Most RG6 has 2 layers of shielding (dual), but you can also find quad-shield (4 layers) cable out there. It is more expensive, and harder to work with.

The last layer, of course, is the rubber. This is just more insulation and there's no point in trying to describe what IT does.

Regular Coax Cable:


Dual-Shield Coax Cable:


Quad-Shield Coax Cable:


These pictures and more information on different types of coax can be found at:
http://www.smartwire.com/

Feedback received on this FAQ entry:
  • Regular cable has an aluminum foil tape applied over the dielectric then the braid, Tri-shield(not dual shield) has a foil tape over dielectric then a braided shield and then another foil wrap and the Quad-Shield looks good.

    2012-09-07 08:21:30

  • ""The caps are a good thing, but most of the cable used is 75 ohm cable so you would need a 75 ohm cap or it will cause an impedance mismatch which can cause you problems."" very important quote, open ports will cause pop outs, from the pole to behind the tv. EVERYTHING MUST BE TIGHT

    2012-01-19 13:17:19 (drcable See Profile)

  • The caps are a good thing, but most of the cable used is 75 ohm cable so you would need a 75 ohm cap or it will cause an impedance mismatch which can cause you problems.

    2011-09-11 20:15:42

  • 4 12 11 Couple things. Yhe coax cable is actually a wave guide. At high frequency, somethink called the skin effect takes over in the wave propagation and the electrons only travel on the surface of the conductor and not in it so a center conductor diameter becomes irrelavant and thinks like quad shielding' proper line tremination, and not exceeding maximun cablle bend raduis wil produce faster, cleaner, less distorted, wavefroms, ie your signal. Also if use have splitters with unused connections, buy 50 ohm terminator caps at an electronics store for them. The center conductor diameter and legnth should insure a good electro/mechanicl joint at the connector mating. Also the materal with the highest electryon mobility, ie GOLD is the highest. So a gold plated copper center conductor would produce the best results. Or so they say. Neet trick. Apply (Fill ) the connector connections with de-electric grease. You get "0" corrsion, for many, years. Also works for aluminum flash lights(no more battery electrolisys, turn signal bulbs, etc. I've pulled apart these items 5, and 10 years later. Still like brand new. Bla, Bla, bla MichaelJoBillyJimBob.

    2011-04-12 15:03:53 (mvallino See Profile)



by Raydr See Profile
last modified: 2002-03-01 09:21:39

Not really. My first step when doing a digital cable install is to see how the TV channels look, and see if there is any ingress.

Just FYI, digital cable will look the same no matter how good or bad a signal you get. When you are watching a digital channel, it is almost as if you were downloading a movie from the internet and watching it on your TV. Even if the signal level is really low, if the digital box and recieve it and decode it, it will still look good on your TV.

Digital Cable does not generally require that the line be as conditioned as a cable modem line. You still want the signal to be good (between -8 and +12), and you do not want an excess amount of ingress or your digital cable box will not get an IP address.

If a cable modem will run on the line with no problems, so will digital cable.

Feedback received on this FAQ entry:
  • All signals coming in are NOT analog. Analog signals appear as a sine wave whereas digital signals are a square wave. (High or low, no in between). All of the signals coming in are RF, but RF can be analog or digital, depending on the application.

    2014-11-10 09:19:24

  • The thing about digital vs. analog loss: analog signals will get progressively worse on a slope as they lose signal - you will get a worse & worse picture as falloff increases. With digital, the impact is not noticeable at first, because the signal is carrying instructions for the digital set top, as opposed to actual video. So, it can tolerate loss up to a point - and when you reach that point, the failure is abrupt. That's why, when you lose signal in a digital set, the entire picture cuts in and out. In a nutshell, either you get a picture, or you don't. There's very little in-between.

    2013-08-23 03:41:23

  • All Signals coming in from a cable are analog. The digital boxes can take the various frquencies and rebuild a digital signal. You loose signal by limiting the strength of the frequencies getting through so that a digital code cannot be rebuilt.

    2012-02-17 20:24:41

  • Yes, but what is the difference between analog and digital? Aren't all the signals in broadband analog?

    2011-03-12 05:51:10



by Raydr See Profile
last modified: 2002-03-15 09:11:00

In other words, if a lot of noise is injected into an old wire, will the signal go through the splitter and get onto the new wire and cause problems?

This really depends on two things: The strength of the noise, and the isolation between ports in the splitter.

The isolation between ports means how much signal is blocked between ports. Most splitters will have between 15 to 25db isolation.

This means that if the noise on the wire is 15db, it won't really affect the other ports, but if it were like 70db or so, it probably would.

This is also why if you hook up a splitter wrong, the TV looks like crap.

Most people won't have this problem.

Thanks to Mike G. for this question.

Feedback received on this FAQ entry:
  • If your old wire from the ground block is feeding the main splitter(s) in the house, maybe into an attic or basement, then the answer to the question is YES, especially if its an old 59 cable or has kinks in it and so on...

    2008-12-06 04:12:35

  • Ok... This is the basics and it is somewhat Case specific. I live in a pretty large apartment building. I also used to work for a cable provider so have a bit more hands on knowledge. I use an amplifier on my cable internet connection and have for roughly 3 years now. There are some specifics in my case that very well may not apply to most. I am in a very large building (over 600 units total) (and thats just in my building which there 4 more 3 to 4 floors each depending). My amplifier is on the main incoming Coaxial. Then split on a three way splitter with my cable modem on the -3.5 connection TV's on the -7's. So that takes out a lot of the overhead interference. My cable modem works fine my internet connection work fine and I have used this setup for many years. So you can try it however, it will be a waste if there is not enough distance and splits between the modem and the amp. Also best to split the connection with the lowest negative number line straight to the modem. If you need more than 3 use a 2 way splitter then a 3-5 way splitter on the second coaxial out to the TV's (the lowest negative connection alway goes directly to the modem). Now if you don't have low incoming bandwidth this will not apply if you incoming is high and you amplify it, the splits then need to come after the amp. I would say negative seven straight to modem and negative 3.5 to -7 to another splitter for TV's. That should control the amperage slightly. However if you have high incoming bandwidth and/or there is another issue it will be a waste of money. You can also check the Coaxial wiring in your house, as sometimes pretty commonly your coaxial house wiring is old. This can be very specific as well in an older wiring scheme your splitters may not accept the bandwidth signal ratio your provider uses(This is VERY VERY common). Even if your splitters are good your Coaxial cable may be old. Or the line in may be old anywhere in between the line in within your house may have a single low bandwidth wire or splitter. These thing will definitely effect your connection. (case in point I once installed cable in a house tv and modem, but modem would lock I ran a new cable into the house to up the bandwidth, did'nt work new incoming splitter's amp and grounding, still did'nt work/new run into house to basement where modem was, no go found a single splitter in the roof under tile's in a small room in the basement which had a tan coaxial wire running to it and was also a low bandwidth splitter changed wire to the splitter and the splitter bam cable modem was locked when i got to computer room).

    2007-09-20 10:59:40 (rapid1 See Profile)



by Raydr See Profile
last modified: 2002-05-12 12:12:43

If you have any older RG59 cable, see any cuts in the lines, or if they detect ingress (noise) on the line, they may require that the line be replaced before you can receive digital services on it.

The reason is that any problems on the line may cause the device to malfunction, work harder than it needs to, or just not work at all. It's probably more preventative maintenance than anything, but it will save you a headache or two down the road.

Feedback received on this FAQ entry:
  • It also has to do with the Upstream Transmit level of the modem on the currently installed lines. If you have multiple splitters or numerous live cable outlets in your home, then a new, dedicated line to your modem/emta will be imperative. The reason being is that you have to realize your modem/emta is heavily dependent on two-way communication with the CMTS on the other end of the node. Every split or even a single, 8+ way splitter is going to make it near impossible for your data device to communicate effectively with the CMTS, resulting in frequent dropped internet and/or voice service.

    2012-08-21 23:37:41

  • Interesting. That would explain why changing rooms which has a different cable doesn't work even after I ensured the cable box outside was sending the right signal to the right port room.

    2012-07-31 00:11:32



by Raydr See Profile
last modified: 2002-08-31 21:49:03

Unless your wall and modem are a really really really long distance from each other (250' or more), it would be an unnecessary waste of wire, room, and money (if it costs). RG11 wire is not very flexible, and a bit thicker than RG6, so it's harder to run as well.

Feedback received on this FAQ entry:
  • i agree with the comment, "...it would be an unnecessary waste of wire, room, and money (if it costs). RG11 wire is not very flexible, and a bit thicker than RG6, so it's harder to run as well.", but for the other commentors - you can just put an rg11 connector on the rg11 and it screws onto ANY f-81..

    2011-07-07 19:41:56

  • Another reason not to bother: quality of signal is a function of the worst/weakest section of cable. If the entire run isnt higher quality, then only if you KNOW you have the big signal drop due to length of THAT run is it possibly going to help.

    2011-06-15 11:37:08

  • Not only is the entire cable much thicker, the F-81s (bulkhead connectors) on the wallplates and CPEs (customer premise equipment) are not built to receive that thick of a center conductor. Connecting a feedthrough style connector where the centerconductor feeds through will result in damage to these interfaces.

    2009-06-11 19:24:09



by Raydr See Profile
last modified: 2002-10-24 22:56:04


Coax Cable Signal (Attenuation) Loss per 100ft
Loss at
RG-59
RG-6
RG-11
1MHz
0.4dB
0.2dB
0.2dB
10MHz
1.4dB
0.6dB
0.4dB
50MHz
3.3dB
1.4dB
1.0dB
100MHz
4.9dB
2.0dB
1.6dB
200MHz
7.3dB
2.8dB
2.3dB
400MHz
11.2dB
4.3dB
3.5dB
700MHz
16.9dB
5.6dB
4.7dB
900MHz
20.1dB
6.0dB
5.4dB
1000MHZ
21.5dB
6.1dB
5.6dB


Feedback received on this FAQ entry:
  • I think the rg59 column is way off it appears to be for 100 meters not 100ft.

    2014-06-25 05:28:31 (maxbrando See Profile)



by Raydr See Profile
last modified: 2002-12-15 10:15:35

I've seen it all when it comes to connectors, from the push-ons, screw-ons, and crimp-ons.

Firstly, prepare your wire! I know that sounds elementary, but I have seen countless times where the shielding isn't completely stripped away and a small strand gets accidentally caught leaning against the stringer. Buy a cable stripping tool and use it! (Actually, the tool is pretty inexpensive, and is easier/safer than using wire strippers or a knife)

Stay away from the push-on style of connectors. They will fall off eventually, or get loose, and ground out your signal.

The crimp-on connectors can also be just as fatal, especially if not crimped using a high quality CABLE crimping tool. Don't use needle nose pliers, or a 3.99 tool, you'll get a 3.99 connection, and that just wont cut it with longer cable runs and digital cable. If you use a good quality connector, a high quality crimping tool, and decent technique in wire prep and crimping, the crimp-on connector is preferred, as it lasts the longest, will not come loose, and will maintain the best overall all connection in the long run.

Screw-on types of connectors were introduced about 10 years ago, but remember that you have to use the proper sized connector for the the cable that you are using. And many homes have multiple sizes in cable in them due to the fact that the industry is constantly changing in terms of what types of materials are currently used and available in stores. Your home probably will have different cable wire in it, especially if some cable wire has been added into it by your brother-in-law, or other friend or relative.

Screw-on connectors will work ok for most homeowner installations, if the wire is properly prepared, and the proper-sized connector is installed tightly on the wire.

So how do I know all about this??? Been there, done that, and learned from my mistakes!

Good luck with your home wiring! And don't forget to check out the FAQs on the types of splitters and amplifiers to use, as most discount and home improvement stores don't sell what you should be using at home.

Feedback received on this FAQ entry:
  • For diy without a compression tool i would recommend the new ideal push-on connectors over the old twist ons https://www.youtube.com/watch?v=m1n-j4H3HDM&hd=1

    2014-06-28 00:19:43 (maxbrando See Profile)

  • Compression fittings are currently the best type on the market. Screw-ons, and crimp-ons allow moisture in the fittings and damage the cable as part of the process of installing them. When I say damage I mean it actually changes the velocity of propagation due to the fact that the "velocity factor mainly depends on the insulating material" which has been crushed by the crimp-on or shredded by the screw-on. I would have to say 90% of outside plant problems are from the drop to the customer premise equipment, and I would have to say 70 - 80% are screw-on and crimp-on fittings. It is these type of fittings that are most often installed incorrectly, induce noise, change the VOP, and allow moisture into the cable.

    2011-09-22 02:22:15



by wmgoat See Profile edited by ergibbs See Profile
last modified: 2003-09-02 11:45:58

Said by Darkk See Profile HERE.

quote:
There is no way you're going to avoid an impedance bump with "flat" coax, and that will definitely introduce undesirable effects on the signal in the cable that are detrimental to TV as well as HSI signals. Not to mention that ingress and poor common-mode noise rejection are a problem with this sort of cable.


Mainly this sort of cable is very poorly shielded, and should really be used as a last resort.

Below is an example of flat coax.
Click for full size


by Axilla See Profile
last modified: 2006-11-03 19:06:00