# Surge protection for cable modem



## splatz (May 23, 2015)

As far as I know these are mostly MOV devices and none of them are perfect but they are better than nothing, even cheap ones, and more MOVs is better. 

I have had the cable co techs squawk and want to take them out complaining that they must cause signal loss. However I ask them to measure signal with and without and every time, the readings have been identical. They think the surge protector must work inline but MOVs actually work in parallel. These days most decent ones made for TV should be rated for gigahertz signals. 

I have tried the ones that look like this,










I have installed them right on the cable modem. I would guess and it is just a guess that you're better off with a surge strip for your power that has coax protection in it, like this one










I figure if you buy a quality brand surge protector you're more likely to get a good quality MOV in there, those little inline ones are cheap and you usually get what you pay for. At best. I prefer the Tripp Lite Isobar with coax. They also make this type for behind a wall mount TV










I have also used this type to replace the cable company's grounding block, they seem to be better quality than the little inline ones.










I would use both protection at the service where they have the grounding block and at the point of use.


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## SWDweller (Dec 9, 2020)

I was looking at the one with the grounding block. I guess I need to get the scope out and do some tests, before and after the protector.
I try and avoid a lot of connections between the device and the source. I read long ago that each connector in a OTA TV cable was 5 db. I do not make up Coax like I used to been a long time and will have to practice before I do the new place. 
I have tried contacting Comcast but since it take 4-7 minutes to get to a human each time I call. ( do you want a text? says the recorded voice) I will not be calling them again for awhile. Last call the guy was polite and really tried but being from India he did not understand most of the terms I was using. Thanked him and hung up before I got frustrated at the level of help I had gotten,


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## splatz (May 23, 2015)

SWDweller said:


> I try and avoid a lot of connections between the device and the source. I read long ago that each connector in a OTA TV cable was 5 db. I do not make up Coax like I used to been a long time and will have to practice before I do the new place.


With RG6 especially, I think signal loss between the CATV service drop and the devices in a house is seldom a problem. 

You can't get into too much trouble with good quality compression F connectors that are correct for the cable, the Ideal ad Klein are both good but my favorite are still the T&B snap and seal. Getting the strip length right is important and any decent compression crimper will work if it's adjusted properly. To me the main pro tip is to use a flaring tool. 

If you think about it all the rigmarole with the terminations is about the integrity of the shield, and keeping out water. The signal is all on that center conductor, the quality of the jacks you're plugging it into is more important than your termination skill.


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## kb1jb1 (Nov 11, 2017)

Most surge arrestors won't protect against a close by lightning strike and they say so on the packaging. It is better than nothing. Also they won't protect against any back ended hits. We just had a lightning storm pass thru and I had 5 customers with almost the same type of burn outs. Nest thermostats, multi zone oil burner control relays, garage door openers, sprinkler control panels, and modems.


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## SWDweller (Dec 9, 2020)

Flaring tool? Not something I remember using. 

I appreviate the lead for the T&B stuff. I have several tools made by T&B and like the way they work. Just what I need is a new crimper.


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## splatz (May 23, 2015)

This was the SnS from T&B that I liked, may still be available at supply houses, looks like Belden bought them out

https://www.lowes.com/pd/Snap-N-Seal-Compression-Tool/50041566


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## emtnut (Mar 1, 2015)

Check out Polyphaser protectors. I've used their in line surge protectors on RF towers.
IMO they are the best.

This is similar to what I've used, but it had the 'N' connections





75 Ohm Type F F/F Coaxial RF Surge Protector, 4MHz - 900MHz, DC Block, 100W, 50kA, Blocking Cap, Bracket Up, Hole Mount


75 Ohm Type F F/F Coaxial RF Surge Protector, 4MHz - 900MHz, DC Block, 100W, 50kA, Blocking Cap, Bracket Up, Hole MountPolyPhaser coaxial RF surge protector (also known as lightning surge protector, lightning surge arrestor or suppressor) IS-75F-C1 is in-stock and will ship same-day as...




www.polyphaser.com





That one only goes to 900Mhz ... not sure what cable frequencies go to these days ?


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## paulengr (Oct 8, 2017)

SWDweller said:


> I am playing storm chaser today. Last night monsoon passed by, close. One bolt of lighting lit up my bedroom and shook the house simultaneously. Dog is in timid mode today. Fried my cable modem, it was unplugged so it was not through the wiring. Have a coax connector outside near the service that is connected to my service ground with a #12 solid. All that I have ever used in the past, 100 bucks for a new cable modem and back on line.
> Been doing some reading and there are pros and cons for an arrestor on a cable modem.
> I would appreciate knowing what ya all use and have had good luck with. IE not screwing up the modem or loosing it.
> 
> ...


1. “Whole house” surge arresters only protect the main panel. Surge arresters are parallel devices, not serial. Anything more than a few feet away from one may as well be unprotected.
2. Coaxial cables have very small gaps between the outer grounded shield and the inner conductor so surge arresters generally do very little because above a certain point the cable fails. They are usually just diodes or caps. Don’t expect it to handle lightning because it doesn’t have to,


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