Originally Posted by
kanebear
One further issue. Amplifiers DO NOT help cable modems. Almost all only amplify the forward path and pass the return without amplification. They also add noise. So if you have an amp, it's best to put the modem ahead of the amplifier if possible. If you don't have enough signal prior to the amp, call the cable co. It's their issue and they need to fix it.
An amplifier *might* help a cable modem. The downstream signal (cable headend to home) is usually carried in the same frequency range as the video, 54 MHz up to 600 to 800 MHz, and usually near the upper edge; the frequency of the upper edge depends on the specific cable system. If the downstream cable modem signal is right at the upper edge, and if the cable signal strength "rolls off" at the high frequency end (decreased amplitude), then an amplifier could help the cable modem signal. The upstream signal (home to cable headend) is carried in the frequency range below 50 MHz, and indeed amplifiers cannot help the upstream signals.