timgr:
If you look at Larry's tvfool report you will see that NM is dB (power, or more exactly power ratio), not voltage:
This is my take on NM:
Andy Lee (who created this forum) did an interesting post with diagrams about NM in the long thread that ADTech mentioned above:
http://www.avsforum.com/forum/25-hdt...l#post15700679
Click on the second set of diagrams (they were attachments before AVS changed the software) for a larger image. If your cursor has a plus sign, click again for an even larger image.
And while I'm at it, there is a lot of confusion about dBmV vs dBm. The dBm scale is used by RF engineers and TV Fool. The dBmV scale is used by antenna installers and cable guys. Both are power, but some people think that dBmV is a voltage scale. It's not; the only thing voltage about it is the 0 dBmV reference level for the scale which is defined in terms of voltage across 75 ohms.
http://www.avsforum.com/forum/25-hdt...l#post16837993