Cold weather = modem dropout

Has the splitter been replaced? Is it a splitter or a directional tap?

I too see more problems in cold weather, but not sure if it's actually modulating electrical properties or if it's just coincidence. My situation has been resolved.

At any rate, clearly you need more noise or gain margin than what you've got. What do your cable modem's signal levels and signal to noise levels indicate? Tell us more about this splitter.

Coax is almost always copper. Couplings are rarely copper. Different metals contract at different rates when the temperature changes. That can cause micro-gaps where the different metals need to connect, resulting in higher resistance, and lower signal levels. The gaps that form as unlike materials contract at different speeds can also allow water to enter, which is a problem in itself, but an even greater problem when it freezes and crystallizes, again resulting in bad connections.

Removing the splitter helps because you're effectively doubling the signal going to the leg that remains connected. It doesn't matter if there is anything connected to the other leg. Just the presence of the splitter splits the signal level. This usually isn't a problem for TV, but it is a problem for cable modems. If you only have one cable drop to the house, the cable modem should have it's own run back to the first splitter. (You can then split the other leg to serve multiple TV's. Just don't split the run to the cable modem.)

There could also be a problem upstream, but given that you have no problem when you remove just the one splitter in your house, it's pretty likely that things beyond your house are in acceptable condition. Just get rid of that splitter after it comes out of the wall, and make sure the modem has it's own run back to the drop. Or see if they can install a separate drop just for your cable modem. Either way, from what you've told us, the solution is within your own grasp because the solution is in your own house.

Well, RCN responded to my e-mail this time by suggesting that a booster might be necessary. I doubt that they'll add a new drop for the modem instead! Incidentally, I used a space heater to blow hot air on the splitter and the wall jack last night just to make sure that neither one was temperature-sensitive. The splitter is a typical passive 3-tap, and I use the 3.5dB tap for the modem. One more thing that just occurred to me is that I might check the outside ground wire and maybe experiment with some other grounding point.

-- Charles Packer

I had a similar problem for several winters until some guy came that actually did some testing. He found a joint under ground that had come loose and let water in. Everytime it got cold the signal got really bad, weather warmed up I had no problems. He cut the connection and put in a new one, this time with a fancy silicon thing around the whole connection to keep the water out. No more problems!!!

I can't recall if I responded to this post earlier or not. I'm concerned about htem wanting to add an amplifier for a cable modem issue. Amplifiers add noise, and generally do not make cable modems happier. They help video quality for TV's certainly, but ideally you don't want them in between your cable modem and the head end if at all possible.

Is this cable company provided, or something you provided? Manufacurer, frequency range, age?

I'd replace the 3 way tap with

line -> directional coupler (1 input, 2 output device )

The high quality DC they used on my setup here is made by Antronix model CMCDT2109T. This evidently has among the lowest insertion losses of available DC's. The tech had to get one of these directly from his boss, so I guess they're more expensive than the DC's they stock in the trucks.

The amplifier they used in the video path is made by PCT and is model PCT-MA2-M. The amp is designed to be cable modem friendly, but if at all possible, all techs I've talked to agree that it's best to have the amplifiers out of the picture if at all possible.

I'd advise against moving any ground point that they've installed. You may make matters worse by creating a ground loop. Where is your current ground going to? Hopefully to a stake shared by other utilities.

If the outside grounding point coupling isn't enclosed you might have a loose connection there or even water in it.

...or hard to find locally. Apparently Radio Shack doesn't stock directional couplers, and a quick Web search didn't turn up that brand, even on eBay. Anyway, this is useful information, and I'll look for the RCN technician to implement something like this configuration; thanks.

-- Charles Packer

They should have such stuff. I'll look around for my old DC -- it was another brand, but had a little higher insertion loss.

Try:

Evidently what my cable company refers to as directional couplers are also known as "drop taps." The concept though is to have one input, one output that has minimal insertion loss (1dB or less), and then a high-loss output (7dB or so). This functionality is in contrast to the typical splitter which features equal loss out of all outputs (-3.5dB for a 2-way splitter).

Good luck--let us know how it turns out!

Best Regards,

Google turned up this site on the first try:

Sounds like there may be a "suck out" on your line. Basically, the center conductor is pulling out of the pin connector when it gets cold. We've been finding them all over for the past few weeks.

The other cold-induced problem may be an amplifier getting overdriven, causing distortion. Coaxial cable is more efficient the colder it is. Amps have automatic gain controls to compensate, but they only do so much.

If your house wire has been installed in the past few years (RG-6), it is most likely a line problem.

Actually, coax is almost always copper clad steel. Couplings used in the home have copper components touching the center conductors.

The problem is more likely to be what is known as a "suck out." That is when the steel clad center conductor on the hardline shrinks due to improper installation at the time the system was constructed. The center conductor actually will pull itself out of the pin connector. Sometimes, when the tempature increases, it will push itself back in, but usually it won't. The fix is to locate the suck out, re-core the hardline and re-install.

The OP must live at the end of a line, since this can effect a large area depending on where it is.

The demographics of my part of town make it probable that I'm RCN's only cable modem customer in my neighborhood. And is the technician liikely to be a subcontractor? If so, maybe he never sees cable modem problems, and that's why in the past they've said such things as my splitter is "worn out." I'm hoping for cold-enough weather on Wednesday, when the technician is scheduled, so that he'll be able to see the results of whatever fix he's going to try.

-- Charles Packer

I had been having problems in cold weather and they replaced the drop from the main line and it solved the problem. The Tech told me the drop should be changed every ten years because hot and cold weather will affect the cable over that time.

It turns out that it was an overdriven amplifier. The technician said somebody would be out today to take care of it. Before calling in to have that check made, though, he did eveything inside the house that he's programmed to do: replace modem, splitter, cable connectors. At least I got a professionally prepared cable out of it!

-- Charles Packer

That occurred in our neighborhood, too. Subsribers in our condo complex were seeing dropped connections and lost packets, and the TV subscribers were seeing frequent pixelation. I asked the field ops manager to check the amp in the curbside vault, and the techs found that the amp was outputting a too-strong signal. The techs I spoke with re-iterated what I've heard from both cable and satellite techs in the past: Especially with digital signals, the signal strength has to be kept within a specified range, and a signal that is too strong is as bad as a signal that is too weak.

*TimDaniels*