recommend a quality CATV splitter please!

[Nate Nagel]

Subject says all...

today I had my cable box lock up and when I rebooted it the picture was all shaky and jaggy, so I took it back to the service center and traded it in on a shiny new one. I found that upgrading to a HDTV box would only cost $2 plus $2/month, and apparently my cable co. (Cox) is surprisingly cool about HD, everything that I already get, I get in HD just by paying the higher box rental fee. So I came home with a shiny new cable box, hooked it up, picture fine but I found that many channels still weren't watchable - just a poor signal. So I got to troubleshooting... I determined that the cable from the splitter to the TV was causing signal loss (took some lengths of coax that I had laying around, connected them together, ran to TV, improved signal, but still not great, but I figured that was because not all of the cables were good quad shield) so I ran some new quad shield. Better, still not good. Bypassed the surge suppressor, better yet, still not getting all channels. Bypassed splitter (have a 4-port splitter screwed to a floor joist in the basement, so I can have TV and cable modem both connected) now it's good. Put surge suppressor back in circuit, still good. Dug in junk box, found an old 2-port splitter, still good. So it's the

4-port splitter that is the problem, even though I just bought it a couple years ago and it was clearly labeled "HDTV" and listed for the appropriate frequency range. GRR!

So...

given the above, what should I buy? Can someone recommend a good brand of 4 or more port splitter that isn't a pile of cheap crap?

OR... is the 3dB or whatever loss between the 2-port and 4-port splitter likely enough to be causing my problem, and I should simply get an amplified splitter? If so, I'd still like a recommend. I would like the add'l ports because future plans involve running cable up to the bedrooms - in fact, I might have been doing it today had not my cable box crapped out.

FWIW I did have the unused ports capped, although I don't know if that really makes a difference or not.

Oh, and this is making the decision as to whether to buy a new TV or not harder. Prices seem reasonable right now, but I don't like having a cable box, am wondering if I should wait until the next gen cable card is available. I know, you guys can't help me with that one (but if any of you have done your research and can recommend a good HDTV, appx. the same size as my old SD Sony projector (53", but not 16x9) or perhaps a little smaller that isn't ludicrously expensive, that would be appreciated too... I don't actually have a HDTV hooked up to the cable box, but I wanted the HD box in case I had guests and they wanted to watch TV in one of the bedrooms, I could just move the box upstairs.

On the upside, now ALL the cable in my house is quad shield save for the maybe 3' long piece between the outside connection and the splitter. I would have replaced that too but it's 90+ and sunny out, and it's working now...

thanks for any help

nate

[mm]

The loss is twice as much. Multiplicatively.

If by capped you mean the proper ends (I forget their name now) the ones with the resistors in them, and a little metal tube sticking out of the end, absolutely they make a difference. At least everyone says so. I haven't bothered to test, because I believe them, but you're in a good position to do so, since you're using more than one at a time. If you mean capped by anything else, it's as if it's not capped.

I doubt if any splitters are cheap crap. At least I doubt if cheap ones work much less well than expensive ones. Except maybe they make a mistake in some really cheap ones and don't reject it.

It seems to me there is no doubt your biggest problem is that you are splitting the signal 4 ways, and then not even using two of them.

Yes, the "caps" make a difference. They keep the signal loss down to what you would have if you were actually using that output. Without the caps the loss is more. But every time you split correctly you lose 3 decibels iirc. That's a lot.

I've found for every two splitters, I need a signal amp. I don't yet split my incoming signal but I have tvs in 7 rooms of my house, and I'm running iirc one 4-way splitter amplifier and one two-way. I only added an amp when the picture was poor.

But you might be better off having a home run from your signal to your cable box, and splitting the output from the box. Well, I guess not if the other cable goes to another box, but I don't know where it goes.

[mm]

I hesitated when I wrote this line, so I reviewed decibels. Although logarithms and therefore exponents are involved, I think "mulitiplicately" was the right word.

WRT sound a bel or decibel is iiuc an aboslute measure of sound level, although maybe that's only because there is already a standard level against which all other sounds levels are measured.

In electroncis a decibel is a ratio, such that P1 and P2 are 3 decibels apart if 10 log (P2/P1) = 10 log 2 = 3 dB where the log is to base 10.

(Hmmm. It seems maybe 3 is approximate, or 2:1 is approximate. or maybe not. It says that 10 times the logarithm of 2 is 0.3. A logarithm is the exponent needed to reach the base, in this case 10. So iirc that means 2**0.3 or maybe 2**-0.3 = 0.1. Is that equation true?)

Regardless, a ratio of 3 decibels represents a 2 to 1 ratio of power. If you lose 3 decibels in a splitter, your power level is 1/2 what it was. If you have two spitters in a row, which is what a 4-way splitter is**, you lose 6 decibels, 3/4s of your power in each output. Of course there are 4 outputs so you haven't lost much power total, but that's little consolation to the tv with a bad picture.

I think, part recall, part spitballing, that logarithms are used because the original use of bel and decibel was for autio sound and heaering. Our ears are such that if there is twice as much power to a sound, the sound doesn't sound twice as loud.

I don't know how much electronics works the same way. It seems like it would only at the output stage and only when the output is a speaker. And also, for example, below a given signal strength, a lot of tv's black out, and above that level analog tv's seemed to give good picture and sound, so that alone is sort of an exception.

But it doesn't matter because we're using decibels and aren't going to stop for a long time, if ever.

**A four way splitter has 3 splitters in it. Each output fromt he first splitter is split again.

A 3-way splitter has 2 splitters. One output is split a second time and the other isn't. It's usually marked which ones are which. If you only need a 3-way splitter, you should either use two two-way splitters, or hunt for a 3-way, rather than lose signal strength and then amplify it again. I suppose in theory with a digital signal it might not be supposed to matter, but things are usually more complicated than that.

[Nate Nagel]

The other cable goes to the cable modem, so splitting the output is not an option. I would like to have cable available upstairs (TV is in basement) which is why I had the 4-port splitter. I figured your typical CATV signal had enough overhead to accomodate a 4-port splitter, and in fact I have only noticed problems recently. I'd been having problems with the old cable box (I missed the finish of the 24 Heures du Mans due to this...) with signal reception, but it was really noticeable when I put in the new HD box. I figure that possibly something oxidized/came loose inside?

I didn't realize that I was still going to experience signal loss without actually using the connections... electronics was not my strong suit. In any case, signal is good with the 2 port splitter, so if I got, say, an 8 port amplified splitter, I should be good to go and have more than enough ability to run cable anywhere I want, yes?

nate

[Ralph Mowery]

I am not sure if they can or will do it for you, but it may be you are not getting enough signal from the catv main line. About 20 years ago I was not getting good reception from cable and had the men out checking. They did some rewiring at the pole, but as I had several TV sets hooked up at the time, they changed the taps on the connection to the main line and gave me more signal. At that time all the wiring was theirs so they had to make things right for me.

Another time I only had some chanels and not all of them. It was not even just the higher or loer ones, but it could be almost any combination of chanels. The man came out and of all things he replaced the connector on the cable comming into the house. Seems that sometimes things can only go partly bad with the cable system.

[Frank]

Comcast put in an "Advanced Residential Amplifier" for me but usually problem is connections and I've had most of my old DIY wiring replaced by them. Last problem I had, I had them check signal to house and they found it weak and had a new underground cable to house installed. Comcast is starting to get like the phone company in that they only do free work up to the house and charge to come inside and now they want a couple of bucks a month insurance. Whatever your situation is, I'd try to get gratis work. If you need insurance, buy it and get work done - you can cancel it later if you want.

[Pete C.]

Go to your cable company and ask them for the splitters you need. They will most likely give them to you at no cost as they have a stake in both ensuring a quality signal to the customer to limit bad word of mouth, as well as ensuing quality splitters are used so they do not present leakage issues that negatively impact their FCC cumulative leakage index scores.

[Nate Nagel]

Didn't think of that, it's worth a try, they seem to be trying to be customer friendly. The lady at the service center today was downright pleasant. I could get used to that, honesty.

nate

[Tony Hwang]

Hi, Let's be logical. All of sudden signal got weak. I ythink nothing wrong inside your house, something wrong outside in the cable box? I'd call cable co. and ask them to check it out.

[mm]

Gawwly, I try to be logical. I thought the problem started when he got the new box.

Nothing wrong with doing that, but a) he made it work by taking out the 4-way splitter, b) the new box might need a stronger signal than the old one did. c) I heard about cable internet that the more people on your block who use cable internet the slower it can get. Could that sort of thing affect cable tv? Can they fix it. The symptoms might be more obvious.

[mm]

Maybe it did with the original box, but didn't you get a new box? I had sort of the opposite, with cheaper parts. I have a dvdr/hdd with digital tuner in my bedroom, and from that it goes into an RF modulator for my analog tvs. From the bedroom it fans out to all the other rooms.**

Then I got a set-top box for my office, and after various other attempts, connected the dvdr co-ax and the set-top co-ax ot the office tv via an A-B switch. Everything was fine for a year. Then the RF modulator failed after only two years. (Maybe that's why they don't sell that model anymore) They're cheap and I bought another for 16 dollars. Well, now, the signal from the RF mod is so strong, it overpowers the signal from the set-top box even when the A-B switch is set on the set-top box. I have to disconnect the dvdr co-ax and put the cable at least an inch from the switch. So what I'm saying is the output is greater. (They sell mddulators that will output on almost any channel, not just 3 and 4, so they'll be no chance of interference between channels 3 and, say, 8 and presumably I can just use a combiner, a splitter used backwards, so when I get a chance, I'll get one.

**(Maybe I should have made them all homeruns but I didn't 26 years ago and I don't feel like redoing the parts that would benefit somewhat from being redone.)

Well I probably woudlnt' know it if I didn't read about it. It's not like a lot of things where you can just stare at it and figure it out.

What was the reason I agreed that home runs might be better? Oh, I think it was so that when I put a set-top box in the bedroom with the dvdr, I'll be able to send one signal to any rooms I want and the other to any rooms I want. Of course I live alone so I'm never going to want to do that, but you might.

Anyhow, I'm sure you can find an 8-way amp, but it might be expensive. You could also use 2 4-way amps and a splitter before them, and I think it will be cheaper and you'll get just as strong, or even stronger output, and it might have more versatility to have two separate amps. ONly you can predict that.

You might ask about this stuff on sci.electronics.repair . A lot of times the answers are way over my head, and I think some get a kick out of doing that, or they are only answering with the other regulars in mind. But you might want to make yourself look stupid, or ask for consumer/novice level replies, or take your chances. Some people defitely give answers understandable by the masses. Or as BP would say, the little people.

[Ed Pawlowski]

"mm" wrote

It may vary with a different cable company, but mine fixed a similar problem. Original rules were you paid for every set in the house hooked to the cable. Of course, people used all manner of splitters. New policy is you pay one fee, no matter how many sets. The cable company came out and for $25 ran wires to each set individually from outside. Better reception and fixed for about what I'd pay for just the cable. My first inclination would be to call the cable company, but others may not be so helpful.

[trader4]

You should be able to use a 4 port splitter without any amplification. Think about how many cable customers have all kinds of multiple splits going on, including splitters AFTER splitters. Doing it upfront with a 4 way is better. Some cable companies recommend splitting off the cable modem with a 2 way first, then splitting after that for TV. That approach gives you less signal at the TV, but more at the cable modem which is more typically the source of problems. If the cable modem is working in your settup, that's a good indication that the splitter is OK, at least the port the cable modem is connected to. Did you try switching the two ports you used on the splitter and seeing if the cable modem still works?

Given the above and the testing you have done, I'd suspect the real problem is a bad cable box. It's not that unusual, as they recycle them and I've seen them handed out with all sorts of problems. Since splitters are cheap, I might just buy a new one to rule that out. I would just get another typical one, nothing expensive. But after that, I'd call the cable company. I'm sure they will swap the box out and they also will come out to check the signal level coming into the house. If it's not what it should be, it's their problem and they will fix it.

If you want to get more technical, if you do a bit of googling on the cable modem you have, you can likely find info on how you can read the info it maintains. That info includes both the receive signal strength and the transmit power, which the unit adjusts as needed. That would tell you what the signal level is. The cable company can read that remotely as well for troubleshooting, but I've only see them use it for diagnosing internet problems, not for the TV side, for obvious reasons. You just talk to the cable modem via your web browser by putting in the IP address for it's webpage.

[Nate Nagel]

Hmm, I didn't know that, I'll have to see if I can do that. Not sure if it'll work but worth a try. I have a wireless router with a firewall connected to the cable modem; I own the router but not the cable modem so I don't have the FM for that one.

nate

[Bob F]

...

If I called them, my cable company would come out and fix the problem. If I asked at the service center, they would give me the splitters they want me to use. Have you tried talking to them?

[Nate Nagel]

No, I just ASSumed that they were similar to the phone company in that once the wiring enters the house it's "yours" and that repairs would be expen$ive. Someone else suggested that, I might call on Monday. Service center is not far from my office.

nate

[Ron]

I've *always* had to have an amp with 3 TV's or more hooked up.

[Ralph Mowery]

If all the wiring is theirs and you did not add anything extra I wold think they would want to repair it for you. I am a ham radio operator and about 25 years ago a neighbor complained I was messing up his cable tv. I was not having any problems with mine so got the cable people involved. It turned out he had added some of his wiring and used substandard cable. The cabel tv use some frequencies that other services use.One of their movie chanels was on a frequency I was licensed to use. As the cable is suspose to keep all their signal in the coax there should not be a problem. They replaced his wiring and all was ok .

[Ron]

My cable company rewired my entire house for free a few yrs ago because I was having problems.

[Pete C.]

The friendly part is due to the cable companies now having significant competition fro satellite and Internet sources. The free splitters part has been around long before competition however.

The signal spectrum on the cable system overlaps the frequency spectrum used over the air for such minor things as air traffic control. Leakage from a cable system is a big issue, and there are annual CLI surveys, sometimes performed by aircraft flyover to check for excessive leakage and map those areas for investigation and repair.

The same leakage points are also frequently ingress points where signals from truckers with illegal linear amps on their CBs (fortunately becoming more rare today due to cell phones and sat links to dispatch) can get into the cable system and cause problems.

Low quality splitters that have low RFI shielding ratings also usually have low frequency range specs, and with cable systems running up to

1GHz, those splitters cause problems with the signal quality.

Similar problems exist with low quality coax and F connectors, so if you as for F jumper cables they will often provide those as well.