Find the cable modem that’s just right for your ISP

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From the January 18 edition of the AskWoodyPlus newsletter

By Brian Livingston

It’s hard as hell to find out the best device you can obtain to connect to an ISP. This can save you hundreds of dollars that you’d ordinarily pay over time for “renting” one.

In last week’s column, I gave you Steps 1, 2, and 3 that determine the
bandwidth you need — e.g., 25Mbps, 100Mbps, 1Gbps — and whether your own modem or
gateway can replace the generic one your cable company provides. (Cable is now the way most Americans get broadband Internet access.)

Today, we’ll go through the remaining steps to identify the exact piece of hardware that’s compatible with the service level you’ve chosen and with your ISP’s standards.Step 4: Do you need DOCSIS 3.0, 3.1, or 4.0?

You’ll hear claims about DOCSIS, so you might as well know what it means. It stands for Data Over Cable Service Interface Specification, and it’s used by all cable modems. Like everything in the computer industry, new communications standards are announced every
year to get you to buy more stuff. Ignore the hype — the maximum theoretical speed of each DOCSIS version (which is never achieved in the real world) is just about all you need to know:

  • DOCSIS 3.0 theoretically supports 1Gbps down, 200Mbps up.
  • DOCSIS 3.1 theoretically supports 10Gbps down, 1Gbps to 2Gbps up.
  • DOCSIS 4.0 theoretically supports 10Gbps down, 6Gbps up.

CableLabs, a Colorado nonprofit that helped to develop these specs, won’t even begin
certification testing of DOCSIS 4.0 products until 2022, so forget about 4.0. Some ISPs require DOCSIS 3.1 cable modems if you’ve ordered 1Gbps service. Others allow 3.0 devices at that
bandwidth level. For future proofing, consider buying a 3.1 model unless its price difference over a compatible 3.0 version is unbearable.

PCMag, for one, states that it doesn’t rate cable modems, because their performance can’t be discerned separately from each ISP’s throughput. Based on each device’s specs — and which
models ISPs say are compatible — the website lists seven cable modems. It recommends ones that support both 3.0 and 3.1. The reviewer, Whitson Gordon, likes the Motorola MB8600 ($150 retail), Arris Surfboard SB8200 ($150), and Netgear CM1000 ($170).Step 5: Wi-Fi 6, 5, or 4? AX, AC, or N? 2.4GHz or 5GHz?

  •  Wi-Fi 6 routers support both the 2.4GHz and 5GHz frequencies. Older wireless devices, such as some “smart home” gizmos, recognize only the 2.4GHz frequency. Many newer devices support 5GHz signals. The 2.4GHz frequency offers greater range, but a 5GHz frequency has faster raw speed. Multiple wireless devices can operate on the two different frequencies at once.
  • The Wi-Fi 6 standard uses a newly developed, 2018-era transmission protocol known as 802.11ax. (It has 10.5Gbps throughput, in theory.) Older wireless devices don’t support the ax standard, of course, but the latest iPhones, iPads, and Microsoft Surface tablets do. Buying a Wi-Fi 6-compatible router allows you to communicate with new products such as these, as well as older, 2013-vintage
    Wi-Fi 5 802.11ac devices (at a theoretical 3.46Gbps).
  • Wi-Fi 4 routers use 2009’s slower 802.11n protocol (which tops out at a theoretical 600Mbps).

You’ll never get a signal anywhere near 1Gbps out of most ISPs. Is buying a Wi-Fi router that’s rated for speeds higher than 1Gbps worth the extra money? Only if you think you’ll own the
device for so many years that your wireless gadgets will eventually utilize that many bits per second.

For a technical explanation of Wi-Fi 6 and several older versions of the standard, see a complete description by mobile analyst Sascha Segan.Step 6: Do you need a standalone Wi-Fi router or a mesh router?

If you live in a dorm room, any standalone Wi-Fi router — no matter how old — will put out a signal that covers your space. But you probably live in a large house with the usual walls, floors, and so forth. In that case, using small Wi-Fi “mesh nodes” around your place will improve your Internet coverage in rooms that would otherwise be dead zones.

Wi-Fi mesh routers are a big reason to replace your ISP’s cable modem. Many ISP gateways have no capability to add mesh nodes.

If you find — using the links below — a mesh gateway that’s compatible with your ISP, get it
unless the difference in price over a standalone Wi-Fi router is too much for you to bear.Step 7: Consult your ISP’s list of compatible cable modems

Now that we’ve covered all of the jargon, we’re finally ready to find out which cable modems are compatible with our ISP’s service level.

Most experts recommend that you buy a simple cable modem and add a separate Wi-Fi router. This enables you to upgrade one or the other in the future. For instance, you might change ISPs, or technology might evolve so much that your old gear just won’t do any more.

Cable modems are rather simple devices, but it’s unwise to buy a modem that isn’t listed as compatible by your ISP. When you plug in your new device, if it turns out not to be compatible, the box would fail to communicate an Internet signal. You’d be stuck with an expensive door stop. Not all ISPs will tell you which third-party cable modems are compatible. Frontier, as we’ve seen above, is hopeless. But the following ISPs do have easily accessible lists. They may involve a questionnaire to determine the speed tier you’re paying for, your location, and other considerations. This will help you narrow down your choices:

Compatibility lists: Charter/Spectrum, Comcast Xfinity, Cox, Mediacom, Sparklight, TDS Telecom, Windstream

If your ISP doesn’t have a link above, call the customer service number to request a list. If your ISP won’t provide a compatibility list, you may be stuck with whatever modems it rents.Step 8: Select the compatible modem with the highest rating

The lists in the previous step are likely to show 5, 10, or more cable modems. How can you easily choose which one is right for your situation?

Fortunately, a site called Approved Modem maintains a separate page for each of 15 major ISPs. Each page describes three or four top-rated compatible cable, DSL, or fiber devices. The ISPs include AT&T, Cable One, CenturyLink, Comcast, Cox, Frontier, Mediacom, Midco, Optimum, RCN, Spectrum, SuddenLink, Verizon, Windstream, and WOW.

If you’re flush with cash, simply buy the device that has the highest rating. Unfortunately, that’s usually one of the more expensive models. If money is tight, select the modem that’s rated
“Budget Friendly.” You’re done!

Whichever device you select, this is one time when you’ll want to read the installation instructions carefully. It’s impossible to explain here the procedure for every device. Your ISP may or may not give you any helpful pointers.

For technical advice, Dong Ngo, a CNET editor, provides a step-by-step procedure to replace a cable modem. Also, the Approved Modem website provides a modem activation checklist. (Those two sites are financed by commissions if you buy a product after following one of
their affiliate links.)

Whew! Here’s hoping that you’ll have a long and happy relationship with your new, fast, and featured-filled modem. Who knows, you might even save some money.

Do you know a secret that we all should know? Tell me about it! I’ll keep your identify totally confidential or give you credit as you prefer. Send your story via the 
Public Defender tips page.
Questions or comments? Feedback on this article is always welcome in the AskWoody Lounge!

The PUBLIC DEFENDER column is Brian Livingston’s campaign to give you consumer protection from tech. If something is irritating you, and it has an “on” switch, he’ll take the case! Brian is a successful dot-com entrepreneur, co-author of 11 Windows Secrets books, and author of the new book Muscular Portfolios. Get his free monthly newsletter

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