I added some notes to
Andy Lee's Noise Margin Diagram to help me understand it better. FYI, Andy created the TV Fool website. His original NM diagrams can be found here in post #397:
http://www.avsforum.com/forum/25-hdt...l#post15700679
The dB values match his original scale; 3 dB for an average preamp NF, 6 dB for the ATSC estimate of the tuner NF, 12 dB gain for a 4-bay UHF antenna, and 24 dB gain for a preamp like the original CM 7777.