CATV splitter?

[Nate Nagel]

I'd like to do a couple things at my house...

1) have at least one CATV "drop" in several locations - basement (for the TV) 1st floor (for cable modem) and at least 2 bedrooms on 2nd floor.

2) possibly run CATV out to the garage (maybe 75' or so away) so I can watch TV while working on car or hanging out upstairs.

I am ASSuming that I would want to add an amplified splitter at the point where the cable enters my house, and then run individual runs of coax to all the locations where I might want to hook up a TV or cable modem.

Problem is, I know nothing about this stuff. Can anyone recommend a course of action?

thanks,

nate

[professorpaul]

If you have a cable modem, the amplifier must be bi-directional. These are expensive. There is a fair chance that an ordinary splitter will suffice. Your cable company usually provides one as part of the installation, and checks the signal levels.

[Tony Hwang]

Hi, Most cable signal is way stronger than it needs to be. Most likely split signal will be just fine for you. If not can install line amp excluding the one going to cable modem. Quality coax, parts will give less signal loss/leak.

[Steve Barker]

You can put an amp on it, but you can't amp the line to the modem. Just run your garage drop first. You may find it fine without an amp.

[Pete C.]

You probably don't need an amp, the incoming signal is likely strong enough.

Home run all the RG6 cables from the drop locations back to a convenient central point.

Get two splitters, a 2 way (3.5db loss per port) and a 4 way (7db loss per port).

incoming cable feed to two way splitter IN. One output from this splitter goes to the cable modem drop, the other to the four way splitter IN. The four way splitters outputs go to your regular TV drops. This minimizes losses on the cable modem feed. The ~11db loss on the other drops will most likely be acceptable.

Put 75 ohm terminators on any drops not in use. Do not under any circumstances use twist on connectors, use quality crimp or compression types only. Make sure all connections are properly tightened. Don't use more coax than you need on the runs but don't short them either, a few feet of slack is ok, 50' is not.

Get your splitters from the cable company as they will be higher quality that what you will find in most local stores. The cable company probably won't charge anything for them. If it's a decent cable company they may even provide the RG6 coax and connectors free or cheap to insure you use the proper components since their FCC CLI performance is dependent on them.

Pete C.

[DerbyDad03]

Could you explain the bi-directional amp comment?

I have a cable modem for Digital TV, Digital phone and Internet access. When the cable company installed the modem they also installed what is labeled as a "1-Way Tap". The main incoming cable is attached to the IN port, the cable from the TAP port goes to the modem and the cable from the OUT port goes to an pre-existing three way splitter. One of the outputs from the 3-way goes to the digital cable box in the family room, one goes directly to a TV and the other goes to the input of another 3-way which has both TV's and more splitters attached to it. The cable guy saw all the splitters and didn't seem to care. (It may be that, in fact, he *didn't* care, if you know what I mean)

In all, I have 10 cable jacks in the house, 8 of which have devices (cable boxes, TV's, VCR's or computers) attached to them at all times. The 2 VCR's are always powered on (they are the tuners for 2 non-cable ready TV's) as is the computer. It is not uncommon for as many as 5 (or more) of the TV's to be on at the same time. I don't have any amplifiers and I don't appear to experience any signal loss, although some of the older TV's may be masking a poor quality signal by virtue of their poor quality picture tubes.

Anyway, I'm still > If you have a cable modem, the amplifier must be bi-directional. These

[Beachcomber]

The Cable you want to use is RG6/U Quad Shield. It should be labeled as such directly on the cable (FYI it comes it white or black and is carried by many electronic stores). Make sure it has the Quad Shield on the label as otherwise it will be of inferior quality. There are lots (and I mean lots) of bad substitutes, cheapie thin coax cables, pre-made cables, etc. which you should do whatever you can to avoid using.

The problem with the cheap cables is twofold. They may have an inferior shield that causes them to pick up terrestrial RF signals (especially TV broadcast signals on the same frequency CH 2-13, which are the same as the cable channels). This usually results in ghosts, diagonal "banding" and a generally poor signal. These poorly-shielded cables may also radiate the signal they carry.

Use professional connectors and the proper crimp tool for RG6/U. Make sure the connectors are tight. All of them. They should be tight enough that they are difficult to loosen by hand, but easily loosened (or tightened) with long-nose pliers. Outdoor connectors should have a waterproof cover of some sort.

Avoid using the amp unless you really need it and even then, split before the amp's input for your cable modem. Amplifiers add noise to the signal (especially hybrid analog/digital cable signals). Realize that when you split the signal two ways, you are sending less than half of the remaining signal to each TV. As said by another poster, this is generally OK because the cable signals are usually strong to begin with and the receivers are extra sensitive and usually have automatic gain control circuits. If you split it 12 ways, you may be approaching the limit to where an amp might do you some good.

Also, the load on the cable is the same whether the TV is on or off. In other words, it doesn't matter how many TV's happen to be on at any one time... The load is constant...and depends on how it is wired.

Beachcomber

[Todd H.]

The amps aren't bi-directional really, it's just that they have a passive return path so as to minimize their interference with the upstream data transmission from the cable modem back to the head end. THe cable modem has its own gain/amplifier for that path, and part of it's "training up" in negotiation with the head end is setting that gain. Without a passive return in an amp, the upstream channel is pretty well doomed.

However, it is best to not have an amp in the cable modem's way at all. The preferred method is to use a directional coupler (aka one way tap) that has minimal insertion loss on the through leg, and 6dB or so loss on the tap leg. The through leg goes to the cable modem relatively unmolested, and the -6dB depleted tap leg gets run that through an amplifier, to feed all bagillion outlets in the home if needed.

In one case I had in a house the cable modem was on the 2nd floor far from place the cable came into the house. IN that case, they had to use 2 directional couplers, and even go to the higher quality, more directional couplers they refer to as DC9's to get low enough return path loss to get a usable upstream path. And because there were tv's on both floors of the home, 2 separate amplifiers were used, but none was in the path to/from the cable modem.

The trouble with amplifiers, even passive return ones is that they add noise, and all you need is one class about information theory to know why noise is detrimental to data transmission.

Best Regards,

-- Todd H.

[DerbyDad03]

Todd,

Thanks for the detailed resp> "DerbyDad03" writes:

[clifto]

Not always. I had a unidirectional Winegard in my cable circuit (Comcast) for some years. Of course, the next time a cable tech showed up, he encouraged me to get it out of the line (probably so they could once again monitor my viewing habits), but I had no problems whatsoever with cable operation for years with that setup.

[Mark Lloyd]

Did you have digital cable?

[Travis Jordan]

Not all cable distribution amplifiers are passive; some are active and have gain in the return path as well as the forward path. That can be important when you have a number of long lossy drops but also need 2-way communications (such as in VOD applications).

As Todd wrote in order to insure adequate signal while minimizing noise levels you need to understand the distribution application thoroughly before adding any kind of amplification. At a minimum you need to be able to measure RF signal levels across the intended use spectrum.

[mgkelson]

I have four RG-62, coax cables coming through a small hole on the outside of my house, under the overhanging eves. All four cables are terminated with a connector and marked with colored tape. The other end of the cables go to various outlets inside the house. Inside the boxes of each outlet, I have marked each cable with the same colored tape code as on the end that's outside the house.

When the cable-company technician hooks on to the outside cables, I explain the situation to him and allow him to take the responsibility of making sure that the hookup works. A couple of years ago, however, I had the cable company disconnected and I converted to satellite. That conversion merely required connecting some short cables from the dish to the outside cables with a coupler.

[kellyj00]

Cable techs are people too, and I've had enough experience with them to say it's probably best to ignore anything they say.

I saw he was about to drill a hole in my brick wall from the outside and stopped him. He was trying to make a 200 foot run from one side of my house to the other, the long way...because "it's not a good idea to use the crawl space if you can avoid it" I didn't even ask why. I'm no engineer, but I've seen many many houses with coax in the crawlspace. So I told him "do not drill a new hole in my brick, if you can find one that's already there, we can use that."

He looked around the foundation and said he'd take it in through the crawlspace vent. I said "let's tap one bedrooms line, which is under the house already, and run it to this other bedroom" "I can't run it through the crawlspace..." I took him in the house and told him where to put the receptacle, he says "can't we just drill through the floor" Me, being a moron...said "fine. I will put on some old clothes, then I will head down to the crawl space, you feed me the wire and give me a tap and I'll make the connection and attach it to your spade bit that you just ran through my carpet and hardwood floor"

So, basically I paid the cable company $30 to send out a college kid on a saturday to drill an unwanted hole in my floor (rather than putting in a receptacle) and waste about 30 minutes of my morning because he was afraid of the crawlspace or just didn't want to get down there. He even gave me his flashlight and crimp tool before I went in.

Do it yourself, Quad shield is the best, rg6 is a little worse shielding but is perfectly fine in my experience. Don't bother doing it if you're gonna use that rg58 coax, it's cheap for a reason... not nearly as good of shielding. And for pete's sake, never ever call the cable company out and leave them unsupervised...I almost had a black coax running all the way around my house about two feet up on beige brick and a hole in my wall.

rant over.

[mgkelson]

-> rant over.

I agree with all of your points. I always do all of my own inside cable wiring by the way and I run the cables through the attic and then down through the walls. I spent a couple of days, a year ago, running some telephone line, coax and LAN wire from the attic all the way to the basement. It was difficult to do because that particular wall happened to have insulation in it. I tried fishing poles and everything else before I finally figured out a way to do it. I actually wound up taking some coiled up copper tubing that I had laying around and then uncoiled it and shoved it down all the way from attic to the ceiling of the basement. I took a hammer and a file and sharpened the end of the tubing so that it would cut through the insulation.

I especially agree with personally supervising the technicians. I allow them to make connections to the wires outside the house and I allow them to install any required devices inside the house, but I specify where those devices will be located.