[GroundUrMast]

How exactly do I interpret the two "db" numbers in the "radar report" ?? What am I looking for there, or more important what range means no way it will work? Just could not find a discussion about this on the site.

http://www.tvfool.com/index.php?opti...57#how_to_read
http://forum.tvfool.com/showthread.php?t=109

The Signal (PWR & NM) columns offer the same information, referenced to different '0' points.

The PWR value is referenced to 1 milliwatt of power. 0 dBm = 1 milliwatt, -10 dBm = 0.1 milliwatts, -20 dBm = 0.01 milliwatts... -60 dBm = 0.000001 milliwatts. To use this information, you need to know how much signal power your tuner or preamplifier needs (or can handle). This should be a wide range, (very roughly, as low as -90 dBm and as high as -10 dBm).

The NM column is more user friendly in my opinion because even though it's derived from the same data as the PWR value, it's zero reference is based on the theoretical minimum signal-to-noise-ratio (SNR) needed to achieve reception using the ATSC (over the air digital standard signal format). An NM of 0 dB (notice the absence of the 'm', because the reference level is not 1 milliwatt) is the theoretical level at which a signal would be receivable... Higher levels are better, signal fade or noise would be less likely to interrupt reception.

In cases where you desire to receive signals that are lower than 0 dB NM in the air, you can use an antenna with gain to improve the net NM (noise margin). Amplifier gain doesn't work the same way though, noise is also amplified and to make matters worse, the amplifier adds yet more noise and distortion. So amplifier gain does not improve net NM... it makes it worse. An amplifier can only help overcome losses and/or noise generated on the output side of the amplifier.