Blind Line & College Ave
Orangeville, Ontario
Cable Levels (Adjust Internet Quality)
Fix slow or dropping cable internet by checking your modem's signal levels ā what the numbers should be and how splitters affect them.
Slow or dropping cable internet is very often a signal level problem, not a speed-plan problem. This guide shows what your modem's levels should be and how splitters and cable runs affect them.
Quick Reference ā A Good Connection
Upstream (Tx) should be between +35 and +51 dBmV
Downstream (Rx) should be between -11 and +11 dBmV
Downstream (Rx) Receive Power Level
This is the amount of signal received by the modem from the transmitter in the cable company head-end.
- -15 dBmV to +15 dBmV maximum for all modems
- -12 dBmV to +12 dBmV recommended
- 0 dBmV is the "optimal" level
Upstream (Tx) Transmit Power Level
Also known as the return signal ā the amount of signal transmitted by the modem to reach the receiver in the cable company head-end.
- +8 to +58 dBmV maximum for QPSK (DOCSIS 1.x)
- +8 to +55 dBmV maximum for 8 QAM and 16 QAM (DOCSIS 1.x)
- +8 to +54 dBmV maximum for 32 QAM and 64 QAM (A-TDMA DOCSIS 2.0)
- +8 to +53 dBmV maximum for S-CDMA DOCSIS 2.0 modulation rates
Recommended upstream signal levels are +35 dBmV to +52 dBmV.
How to Check Your Levels
Most cable modems have a built-in status page that shows the current signal levels. Log in to the modem the same way you would to change your Wi-Fi settings and find the status page (commonly at 192.168.100.1 for standalone modems).
You can buy amplifiers and attenuators (reducers) for the cable line to bring the levels into range.
Splitter & Cable Loss
Every splitter drops the signal on the line. Most splitters have the loss printed on them ā here are the standard values:
| Item | Loss (dB) |
|---|---|
| 2-way splitter | -3.5 dB |
| 4-way splitter | -7 dB |
| 8-way splitter | -11 dB |
| 100' RG6/U QS cable | -5 dB |
| 100' RG59 cable | -7 dB |
Tip
Put the modem on the first split from the line coming into the house, with as few splitters as possible before it. Remove any unused splitters entirely instead of leaving open ports, and cap unused splitter ports with 75-ohm terminators. If your downstream is fine but upstream is too high (near +52), that usually means too much loss between the modem and the street ā an amplifier won't help upstream on most cheap units, so fix the splitters first.
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