Will coaxial cable installed in the 1970s be fast enough for internet speeds 400 Mb/s+?

Question

We are just about finished wiring CAT6 cable all over our house. We also plan to upgrade to 400 Mb/s internet speed from our ISP. We currently get 200 Mb/s from our ISP, and I have seen as much as 230 Mb/s from an internet speed test using our old CAT5e cable (so its proven our coax cable can handle at least that much).

Will we even be able to take advantage of these faster speeds (400 Mb now, maybe even 1 Gb in the future) with coaxial cable that is 50 years old?

Other info: I have read that the length of coaxial cable can affect the speeds... I estimate there is about 50 ft of this 50 year old coax cable. I could not find any print on this old cable saying what type it is. It leads into about another 45 ft of RG-6 coaxial cable (I'm assuming the RG-6 would not create any bottlenecks).

Answer 1

Other than the pesky but unknown question of "exactly which type is it" coaxial cable has not really changed much in 50 years. If it's not defective, it will probably work. Otherwise, it's 50 feet, replace it, or let the provider replace it. Most providers will allow you to try a new service speed and decline if it does not work for you at the claimed speed.

Cable length (new or old) adds to loss of signal strength, and at some point that will affect what service you can get. More expensive, fatter, harder to bend cable can have less loss for the same distance at the same frequency. But it's rarely an issue in normal home-scale cable plants serviced by decent cable-company infrastructure (where they deal with providing enough signal strength to service most of their customers houses without extreme measures being required.) If your current modem permts you to view the signal strength it's getting, you might get some insight - otherwise the cable tech has a fancier meter that will let them know if it can work when they hook it up.

Why you "upgraded" from "perfectly happy to do gigabit" Cat5e to Cat6 for the prospect of possibly having 400 Mbit or even 1 gigabit is beyond me, though.

Answer 2

In my experience, where there are problems with old coax for new internet, it isn't the cable itself causing the problems but rather the connectors, splitters and other "stuff". But the end result is that if it worked for 200 Meg. it will very likely work for 400 Meg. Where I see problems, they generally happen at much slower speeds, so since you got to pretty high speed, you should be set for a while.

The one exception is 100 Meg. as a limit based on Ethernet network type. My brother on 75 Meg. (which is, to be honest, enough for the vast majority of people unless you're frequently doing some really huge downloads, running your own data center, etc.) just discovered his FIOS is limited to 100 Meg. because the ONT only has a 10/100 port, so if ever decides to go past 100 Meg. he will need an ONT replacement (which is a telco project by definition).

As noted by Ecnerwal, CAT 6 is overkill for most residential/small office installations. Nothing wrong with it for new connections, but no reason to rip & replace functioning CAT 5e unless you truly need more than Gigabit speed. That can be the case if you run a big network in your home or office - e.g., I put in a Gigabit switch years ago even though my FIOS is < 100 Meg., so that I could handle large transfers between local computers faster. But unless your computers have faster network cards, CAT 6 will be as useful as gold-plated HDMI cables.