Surge protection needed for a cable modem?

[Felecha]

Just got cable internet access here on my dirty little road in rural New Hampshire. Love it!

But ... I just realized the other day that it's hooked up straight to my computer and ... there's no surge protection in there! Of course my old dialup connection went through a surge protector, so I looked at the cable and thought, "There's a perfect path for a lightning strike!".

I called the cable company's tech support and asked about it. Surge protectors as I know them have phone jacks, but not jacks for RJ-45. What do you do? He said, "Nah, man, you don't need any protection, the system is grounded and a strike would go to ground first." I didn't know any way to question that, but it left me still not 100% sure.

I actually have it networked, first into a LinkSys router, then out to my 3 home PC's. I wasn't going to tell the tech guy that, since the cable company frowns on networking their service. But I should tell you guys, if it matters.

So, is he right, am I OK? And if not, what do I do to protect my network?

Thanks

Felecha.

 

[spidey07]

Well, I've had numerous piecies of equipment (thousands of dollars) fried from cable TV wires. they sell surge protectors that also protect cable. Can't hurt.

Lightning is very funny and I don't take chances anymore.

 

[sohcrates]

i agree. surge protectors with cable in's and out's are pretty inexpensive these days...definitely worthwile considering all that is hooked up , especially on a LAN (i.e. make sure you install it before the wire enters cable modem, but you prolly already figured that)..i'd assume any dB loss would be negligible through it, so it shouldn't affect your signal strenght.

 

[Felecha]

Er, um ....

But there's a black coax-looking cable in from the road, that enters the cable modem, and out the other end goes a regular cat-5 cable with RJ45's, into the router. The cable modem is owned by the cable company. I was figuring that whatever I put in the line would be between the modem and the router. I don't mind plugging the cable in and out of the modem and the router, I don't think I can do anything that "they" wouldn't like, but I'm reluctant to fiddle with the incoming connection. The installer guy was more than a little cold and distant about the idea of networking my house off of their modem. "Sir, I won't say anything about that. We don't support networking and we run one cable directly to one computer, and give you one IP address." That put an end to my hope to question the guy a bit about the network stuff since I've got into it without any experience, just opened the boxes and read the instructions for router and cards. The paperwork I signed for the installation included a promise from me that I would not move "their" modem anywhere else in my house or fool with "their" setup.

Anyway, I did get "my" network working off of "their" modem, and I love it, and I'm more than a bit pleased with myuself for getting it up and running. But I'm a bit cautious about what I do with "their" hardware. So I thought a surge protector between the modem and router made sense, and if lightning blows out "their" modem, well, it's theirs, right? And looking at the regular surge protector I already have, with two matching phone jacks, I thought anything I bought would also have a pair of RJ45 ports.

 

[sohcrates]

woops...i thought you were talking 'bout coax surge protectors...either way , ANY protection helps..whether you feel comfortable messing with your cable provider's stuff is up to you.

good luck!

 

[PrinceofWands]

First of all you're way too paranoid about the cable company. I guarantee you they don't care at all, they just want you afraid. I didn't like the way they set up my coax so I completely rewired with better grade cable and a more logical splitting pattern. It improved my reception significantly. I've moved the modem a number of times, although unless you know someone with line tools you'll have to call them if you change cable jacks. I've had my modem in a windowsill, and also used to prop up a bookshelf for a while . Most brands of modems have built in suppresion devices, but they're not terribly advanced.

My advice is to check radio shack for coaxial protector and definately protect your Linksys however you can. You can plug the modem into a surge protector but make sure it's a good one as you can't afford voltage fluctuation with your modem.

 

[Felecha]

I've been plowing snow for two days here in the big storm that made the national news, just got back to check in.

Thanks for the replies.

F

 

[dirtboy]

I have had concerns about lightning damage as well. Our cable comes to the back of our house, from a poll and at the house there is an earth ground. From there, one line goes to the CATV and the other to the modem. So far, they have only had to replace my modem 3 times. I don't know if it was caused by a surge or not. Good thing for the lease!

 

[Felecha]

Can I reopen this one?

I did go to my local radio shack. The guy there talked way over my head, I'm afraid. He was telling me that real protection is only possible if there is one and only one device doing all the protection. I already have my computer, monitor, printer, etc. plugged into a UPS. I expected I would add protection to the cable separately, but he was telling me that if the cable and the power are separately grounded, then protecting each individually leaves me susceptible to surge problems still. His explanation involved something about inductance and how the two separate grounds would allow for the voltage to go up and down between them momentarily, apparently allowing surges through the lines that neither surge protection device would break for.

He said the only way to do it is to have one device doing the job. But I lamented that with 4 separate computers, I would have to have 4 separate protectors. I of course have regular good old protectors already for each one, but none of them have a port for RJ45's. I would have to buy 4 new rigs, and apparently something not ordinarily found on the retail market. He said he would have to look his catalogs himself for me.

He also pointed out that I need to protect the power supplies for the cable modem and the router while I'm at it. I didn't think of that!

Later I talked to the guy at Staples, who is usually pretty good with stuff like this. His idea was that I should just connect the ground for the cable modem, which hooks to the telephone ground, to the ground for the power. That sounds good to me.

Any ideas from any electrical engineers out there?

 

[crazychicken]

i got a surge protector designed for tvs that works just like the normal surge protectors for phones, but it has co-ax in and out so it protects the modem.

cya
david

 

[JackMDS]

I would say that in normal situation in home environment there is two-protection concern.

1. Surges that come through the Power source i.e. the 110VAC, this is best protected by plugging the sensitive instruments to UPS, and or good surge protector.
2. Surges and Spikes that come through the signal feed like Cable, and Telephone lines.

In case of cable, there is a special adapters that is installed put outside before it feeds into the house.

This arrangement provides solid grounding. One simple solution is to install Grounding block. RadioShack # 15-909 $2.99, with Grounding Rod #15-530 $8.99.