Really "need to" replace older CATV cables? Would my cable provider really filter my line against my will?

The problem could be standing waves. I don't think any FSM is accurate enough to detect that. First of all the cable modem requires a specific frequency, but it also requires the sidebands. In some cases standing waves can cause complete eradication of 400,0001 Mhz yet barely affect 400.0002 and 400.0000 Mhz. If this happens the signal strength is fine bit there is so much distortion in the modulation that the signal is near unusable.

Remember reorienting the antenna to get rid of ghosts in a TV picture or distortion in an FM signal ? It is the same thing. Standing waves are very much like multipath in their effects on signal quality. Some old FM tuners actually had a scope built in to display multipath. The optimum signal would display pretty much a flat line. Moving the antenna would cause dips in the line, and that is what causes distortion. Measuring signal strength just doesn't cut it.

He may have been blowing smoke about the TVs polluting the signal. It's hard to believe the effect would be a big problem if they meet FCC requirements on radiation. But then it's possible that he was just attempting to improve the signal as much as possible. Hard to say. I know people get alot of lip service when what they want is service, this one is tough to call either way. Maybe he just did what he could.

But FCC requirements say nothing about antenna input impedance, if that is off it can cause the standing waves. I'm not sure if a filter would take care of that completely. It seems it should but I know better, things do not always work as they are supposed to.

If you are talking a "thinner" cable than what is used tody it is probably RG59 or RG59U, both of which attenuate the high frequencies significantly. If the cables and the fittings are perfect this is simply due to capacitance and is not likely to cause standing waves. But then those things are not likely to be perfect, and may not have been in the beginning.

The only way to tell really is with a sweep spectrum analyser, and those things will not be on the truck due to cost. The cables could also be checked for that using a time domain reflectometer, which would be even better, but look up the cost of one and you'll see why there was not one on the truck. It's simply too expensive.

It is possible that it is the cables, and you don't need a licensed electrician for that in most localities because there is no power involved. But finding someone who really knows how to hide the wires is not easy. Most higher caliber electricians can do it but they usually simply refuse because it is a ballbuster. I can do it, but unles you live nearby it is not going to happen.

Do your neighbors have this problem ? If not get them to run a line straight into your existing cables and see if the problem persists. It will have to be attenuated to the same level you have now to make it a valid test. If it is found to be in the wiring in your unit, which can only be proven by others in the same complex using the same modem, with a couple of other requirements, it may be a matter of fishing a new cable into wherever it splits off into your unit. It is very hard to be absolutely sure, and the shotgun approach may be a better idea - which is to replace all the cables in your unit.

Now is another factor, there is more than one carrier frequency involved in cable internet distribution. These two modems might work on different frequencies, and due to the nature of the effect of standing waves that can make all the difference in the world. So now the question is, since they got you hooked up with the other modem, why not just leave it that way ? Is there a rational explainaition for that ? They may have reasons we may never know, but it seems to me if they want that check every month they should do whatevwer it takes.

So my highly technical ass with all the experience has this advice - Tell them to take their service and shove it up where, well make sure it doesn't get a sunburn. Tell them the wires are fine with the old modem, why change it ? Tell them you are considering other options and since they can't provide what you are paying for the contract is null and void - they are in breach. You should see some action.

See to them it's not just the monthly check, it's market share. Therefore threatening to quit works wonders. Got someone I know a free wireless router a few months ago, but she is sharp. Not when it comes to computers, but when it comes to money. She was head of the purchasing department before she retired and she gets things done. Threatening to do business elsewhere has alot more impact to companies like this than one might think. Having more customers does alot, it can affect stock prices, the D&B rating as well as their advetising plans. Use it against them if they don't deliver the goods.

I don't think you know what you're talking about. Interference effects generally vary continuously -- they do not occur at one frequency, then miraculously disappear at another.

Given the age of the cable, it's possible it's deteriorated to the point where it needs replacement. I was reading something recently -- possibly in this group -- about the way the outer plastic insulation can actually "attack" coax dielectric. Or something like that.

I had problems with digital cable service being unreliable (house is

A generic 'booster' won't work on a digital system, as the cable box talks back to the cable office to get the program you want. You should be able to find one on ebay for under $50.

If the problem is loss or poor frequecy response in the old cables, the amp should help.

I dropped Comcast as cable TV provider because the service was so poor (pixellation, loss of signal on individual channels, etc). I was never tempted to use their internet or phone offerings because their TV up-time wasn't acceptable. I now have AT&T Uverse and the TV is close to excellent. Among other things, the router (everything is TCP/IP) logs loss of signal and reports in. The internet download is

John

The good news is that the modem has managed to remain online continuously ever since the technician left. So perhaps, for now, even though he is telling me I should replace the older cables, perhaps what he did improved the signal enough so that this modem can stay online. I got above 9 megabits per second downstream in a speed test last night, which isn't the fastest in the world, but it's triple the speed of DSL. If the outages happen again I can rule out the older CATV cables, by moving the modem to a newer line/jack, and then disconnecting the older cables from the system for a few days.

There already is an amplifier in the system. It was originally installed when a Cable modem couldn't work upstairs in my office when I first bought this place and had cable for a month or two. The amp was originally on the whole system, but my one Sci. Atlanta Box in the kitchen (actually a kitchen with a den area) eventually started getting interruptions, and I was told that the signal to the box was actually too strong so they added a splitter so that the signal going to that room isn't amplified.

I'm still finding it a little "creepy" that I was being told by the technician that someone at the cable company can go around at my area and decide to slap a filter on my entire line at their green box, or slap a filter on a group of people's lines in my development without telling anyone. It seems to me that if they did that, then I should be able to move the modem to one of the newer CATV lines that were added after this place was built with a wireless wrouter, and insist that they only slap filters on the older CATV cables as a solution rather than filtering out my whole system.

They sent me a new modem because it's their policy of sending one to a new customer. The older modem is like 10 or more years old, and the speed I was getting wasn't as fast as a newer modem. If I could find out what frequency it uses, then maybe the new one could be "hacked" to use the same frequency as the older modem?

The reason I got Cable is because I have DSL too, and it was starting to really act up, and I got fed up. For the time being, DSL actually seems like it is back to being reliable. A major piece of equiment failed on their end that and they had to replace it. In my opinion it was acting up before it failed completely and causing some major DSL outages and some days of frequent intermittent outages before they fixed it. I signed up for Cable while DSL was troublesome, but Cable proved unreliable too, at least up until now. I'm gonna keep both for a while because I need a backup in case one has an outage. I may drop one of the two and get a mobile hotspot as a backup. Is Verizon any good for that?

I won't tell you who my DSL provider is but lets just say the name begins with a V and ends in an n, and their DSL has had frustrating intermittant outages at times. Their tech support is not located in the US, and if you call them when there is an outage in your area, it can take several hours just for them to confirm you're not the only person having a connection problem, and they make you go through all kinds of steps on your end to try and rule out that it's your modem, etc.

J.

Unless, you're in the general NYC area, that's probably not feasible.

Who installed the original coax? If it was the builder or an electrician, it will be the cheapest crap they could find, and was intended for a MATV feed. Some was low grade RG-59 with a copper braided shield that wasn't even good enough for the VHF channels.

The fact that you even need an amplifier indicates the coax is defective or substandard.

You don't know anything about how a CATV system works. Filters are used on individual drops to block channels or groups of channels or services that aren't paid for. There is supposed to be a small directional coupler to split the cable modem form the TV feeds to drop the level to what the modem needs, and reduce possible interference.

They all use the same frequencies for uploads and downloads. The design of the newer modems allows a higher data rate. In fact, their business customers can get a 40 Mb/S data rate if they want to pay for it. Road Runner now offers it to residential customers in limited areas. It all depends on how much spare fiber optics is available in your area. Internet is carried over 'Fiber Enhanced Cable TV' which means they use a piece of fiber optic cable for each area, then it is converted to RF and connected to the system, for that limited area.

http://192.168.100.1/ will display the user interface on my S-A Cable MODEM.

Name WebSTAR DPC2100R2 Modem Serial Number ******** Cable Modem MAC Address ***************** Hardware Version 2.1 Software Version v2.0.2r1256-060303 Receive Power Level -3.9 dBmV Transmit Power Level 51.0 dBmV Cable Modem Status Operational

DSL is a joke in most places. It is a low grade RF over a copper pair system that uses old and failing copper telephone wire to deliver the service. If you have the slightest problem with the pair, and it fails.

Ingression and radiation are continuing problems for CATV system operators. The cause is two fold. Old or damaged cable, and tampering or low grade work done by their customers. We used the 'Sniffer' brand of monitors in our systems in all the service trucks to monitor the system whenever they were on the road. The installers had to find a safe place to pull over and call the dispatcher, to get the lead tech out to find the source as soon as possible.

Sigh. By design the antennas used in CATV headends are all 75 ohms. They aren't cheap radio Shack junk, but are single channel antennas made for the CATV business. Some weigh in the hundreds of pounds and cost several thousand dollars.

Another know nothing answer. Filters have to be designed to work at

Never heard of a TDR? CATV systems had a sweep test system for anual 'Proof Of Perfomance' testing at least back to the early '80s.

What difference does that make?

How do you propose they make sure the signal levels are in the required range for the cable MODEM?

It would make more sense for the CATV tech to swap ports on the line tap, or just replace it.

Sigh. Most in the wall wiring is done by idiots who staple it in place. My crew had to bust a lot of drywall to replace bad coax, and a lot was bad becasue 'Bozos 'R' Us' put a staple through the coax, inside a wall.

Really? Were in the DOCIS standard is this information?

The average installer is clueless about cable MODEMs. Some can barely do more than hook a TV to an existing drop. You need a lead tech, or a cable internet trained tech.

One thing that I'm wondering....with regard to the technician claiming that the cable company would slap a filter on an individual residence, or group of them, if any ingress is being introduced into their system by those homes...it seems to me that would prove that they don't really have a fiber optic system as they claim. In other words, lets say it's really true that my cables are pulling in some background noise. If they're so darned concerned about ingress affecting their precious little cable network (ha!), then it's likely because they don't really have a fiber optic network from the pole and beyond as they imply/claim they have. I'm failing to understand how, if there really is fiber at the pole and beyond, then the ingress would survive the conversion from a CATV Coax signal to fiber optic signal.

J.

Even in a fiber-optic system, at some point the signal has to be converted to RF for your TV or set-top box.

I don't know if there are systems that remain optical all the way up to the set-top box.

No, but Verion's FIOS is fiber right to the house.

The fiber may stop a mile or more from your house. All it takes is a single damaged cable, or loose connector to cause ingression. I used to design the systems.

is a

We have Comcast Cable and in our town signals are sent into town from the head end, a distance of about 10 miles via fiber. It is my understanding that they arrive at a "node" where they are converted to RF and then conventionally distributed throughout the town. Our public access town channels used to return to the head end on a"T" channel, a frequency usually below channel 2 and then the cable company would up convert them to some cable channel and put them in the line up. These days the "T" channels are gone and our public access channels return to the head end via fiber.

Ingress was a big problem on some of the older RG59U stuff. There is still aircraft radio, public safety, and low band over the air radio signals out there that can get into a cable and raise hell with a CATV system. That's why cable companies really hate that old stuff. Much of that cable was nothing more than a center conductor surrounded by a foil shield with a few "drain" wires for show. It was really terrible crap which didn't even qualify as good clothes line. Lenny

The return channels (T) are used for internet, VOIP and to order pay per view. I used two T channels on the system I maintained near Cincinnati. One on the main loop, and the other to connect a sub split to a mid split community loop. The interface between the two cable companies was a single Hetrodyne Signal Processor to convert the alien system's channel 12 to T-10, which was fed back to our headend. The amplifiers required two pilot channels. We used 2 and 12, so our forward signal was on Ch 2. This was fed into their system, and routed to their headend. They were already set up with a Ch 6 feed from one school, so we let them keep control of the loop. I designed the headend, which was another pair of RCA HSP, as well as the pole mounted HSP at the interconnect. I set the levels in the shop, and was only off .1 dB at the interconnect point. Not bad for hardline that was hung five years earlier, and never spliced. :)

The biggest problem with the return channels is noise. Every source connected adds noise to the system. Some return amps were switchable to disable them, allowing the CATV operator to route a single source to the headend. This made sense when it was used for nothing more than live remote feeds. Fiber breaks it into small enough nodes that there is no need for switching, and in most cases, no amplifier for that direction.

It was still better than the original copper braid coax. Even double copper braided with a silver plated copper center conductor was horrible. That wire sold for over $1 a foot in the early '80s. Most ingression/radiation problems with foil shielded coax is from bad crimps at the connectors, or wire that has pin holed and water got inside, which wicks in the dust and salt on the jacket. That eats the foil.