When you’re setting up your modem, smart TV, or home gateway, one of the most overlooked variables is the length of your coaxial cable. You may be asking:
“If I run a longer coax cable from the wall to my modem, will my internet get slower?”
That’s a fair question — and the answer is yes, potentially, but it depends on what kind of coax cable you’re using, how long the run is, and the quality of the signal path.
Let’s break it down.
How Coaxial Cable Affects Internet Transmission
What Signals Travel Through Coaxial Cable?
In internet installations, coaxial cable is commonly used in:
Cable broadband systems (via DOCSIS modems)
Satellite or CATV feeds
Ethernet-over-Coax (EoC) bridges in buildings
These signals are RF-based and operate at frequencies ranging from 5 MHz to over 1000 MHz. The higher the frequency, the greater the attenuation (signal loss) per unit length.
What Is Attenuation and Why Should You Care?
Attenuation refers to signal weakening over distance due to resistance and dielectric loss in the cable.
Longer coax = more attenuation More attenuation = weaker signal to your modem or TV box Weaker signal = slower speeds, higher error rates, or disconnections
Does a Longer Coax Cable Really Slow Down Your Internet?
Yes — But Only If the Cable or Setup Is Wrong
A longer coax run can:
Drop signal levels below the modem’s threshold
Increase noise levels (lower SNR)
Cause your modem to operate in fallback or reduced-speed modes
But if you’re using the right cable type (like RG6 or RG11) and your total run is within spec, you may not notice any speed drop at all.
Signal Loss by Cable Type and Length
Cable Type
Frequency (MHz)
Loss per 100 ft (dB)
Recommended Max Length
RG59
750
~10.8 dB
≤50 ft (avoid for internet)
RG6
750
~6.5 dB
≤150 ft
RG11
750
~4.0 dB
≤300 ft
Rule of thumb: Stay under 7 dB total loss for cable internet to avoid drops.
Is Your Coax Run Too Long?
Ask yourself:
Is your coax cable run longer than 150 feet?
Do you use multiple splitters or wall outlets?
Is your current cable thin (RG59) or old?
Are you experiencing internet dropouts or slow speeds?
If yes to any of the above, it’s time to rethink your setup.
Common Scenarios Where Length Becomes a Problem
Case 1: Multi-story homes
Basement modem to 2nd floor TV = 60+ feet of cable Solution: Use RG6 quad-shield, avoid unnecessary splitters
Case 2: Commercial buildings
Main feed to distribution rooms = 200–300 ft Solution: Upgrade to RG11 backbone with amplifier if needed
Case 3: Signal split to many devices
More than 2–3 splitters? Solution: Inline amplifier and signal balancing
How to Improve Internet Signal Over Coax
Use the Right Cable Type
Scenario
Recommended Cable
Short run (<100 ft)
RG6
Medium (100–200 ft)
RG6 Quad Shield
Long (>200 ft)
RG11
Limit or Replace Splitters
Use low-loss splitters, and never daisy chain more than two.
Avoid Old or RG59 Cables
RG59 is for analog TV, not for DOCSIS broadband.
Check Terminations
Loose or oxidized F-connectors can cause 20–30% signal loss.
Real Case Study: Coax Length vs Internet Performance
Client: 3-floor private villa in Malaysia Issue: Intermittent slowdowns on upper floor WiFi Setup: RG59 cable over 80 ft, multiple splitters Fix: Replaced with RG6 quad shield, centralized modem Result: 45% consistent download speed increase, stable streaming on all floors
FAQ
Does a longer coax cable reduce my internet speed?
Yes, if the cable is too long or low quality, signal loss will reduce speed or cause disconnections.
What’s the ideal coax cable for a 4K TV and modem?
Use RG6 for typical installations; for longer distances, use RG11.
How long is too long for coax?
Above 150 ft, use RG11 or a properly amplified RG6 system.
Should I replace RG59?
Absolutely. It’s outdated and not rated for modern broadband frequencies.
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