Cable modem signal levelsWhat do signal levels and SNR mean ?
2003-06-24 (updated: 2009-11-09) by evrensen
What is a good "Signal Level" ? What is "Upstream SNR" ? What is a good signal strength ? If you want to know the answers to those and other similar questions, read on.
The basic information about your particular brand of modem can probably be found at the manufacturer's website... The most taled about issue when having problems, and the first thing to analyze, is the status of the signal to your cable modem, so what does it mean ?
On your cable modem manufacturer's page you might find terms such as: downstream SNR (signal to noise ratio), downstream power level, upstream SNR and upstream power level. Here's what all those mean, and a general guideline of what constitutes a problem:
Downstream SNR shows the strength of the signal to your cable modem as compared to the noise on the line (signal/noise). If the noise level increases the SNR value decreases. So, then high levels are good for the SNR. This number should be at 30 or more. If the SNR goes below 30 than you will probably start to experience some problems, such as intermittent connection, packet loss, etc.
Downstream Power shows the power of the signal your cable modem is getting. The level of the downstream power should be -15 to 15 dB according to most manufacturers' specs... However, it is best for that level to be in the -8 to 8 range.
Upstream SNR shows how much signal the head end is getting from your cable modem, compared to the noise level. "Head End" refers to the point of reference that is the central point of the local network of your service provider. Anything above 29 is good. Just like the download SNR if the noise level increases the upstream SNR decreases.
Upstream Power shows the level of the signal from the cable modem to the provider. This number should be lower than 55dB. The lower the number, the better your connection.
All those numbers can aid in determining many potential problems with your cable modem connection...