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As far as the -15 to +15 range goes, that's not actually mandatory for the modem to work. It's the ideal range, because in most cases, at -15 the noise is starting to get bad.

Here's an analogy:
Say you're in a filled room having a conversation with someone. The volume they are speaking at will be the signal level. The volume of the people around you is the noise level.

Now, if the person speaking to you is at a low volume, you're going to have a hard time making out what they're saying because of all the noise.

HOWEVER, remove that noise from around you, and you can hear that guy just fine. If you have very little noise, you can operate at lower signal levels reliably.

I've had a modem running at -32db before, because it was running through a 300MHz splitter.

Feedback received on this FAQ entry:
  • The best signal for a modem to run on is 0db, we here the specs for operational signal is between -10 and +6db. Upstream 51db is the max and 33db is the min. Then snr has to fall between 31db and 39db. I would say your modem which is at over 10db is running too hot. And your upstream power level is also a bit high for having such high downstream level.

    2008-12-06 03:50:26

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by Raydr See Profile