How do I read signal and noise ratings?
These numbers are given in decibels (dB) and are expressed as negative numbers. So, a lesser number, like -10 dB, represents more strength than -70 dB. The values are logarithmic. A signal amplitude change of 6 dB is equivalent to a factor of two; 20 dB is a factor of ten.
Based on this Forum-post (
http://www.dd-wrt.com/phpBB2/viewtop...?p=14747#14747)
Signal -> Low is good (well -10 is good, -98 is bad, mathematically -10 is higher than -98.)
Noise -> High is good (-98 is good, -10 is bad, -70 would be pretty bad in the real world)
SNR -> High is good (should be the same as difference between noise and signal, a difference of 20 would be great, a difference of 1 may barely work)
Signal Quality -> High is good (somewhat like SNR but indexed to 100 with noise as the base, percentage of the best theoretical available quality in regards to your local-noise, difficult to explain *g*)
Examples would be:
Signal Noise SNR Signal Quality
-82 -98 16 14%
Signal - Noise = SNR
-82 - -98 = 16
Signal/Noise * SNR = Signal Quality
-82 / -98 * 16 = 13.4%
Typically, noise will be -92 which means you should get a connection with a signal as low as -92. However, expecting to hold a good connection with a signal less than -85 (e.g. -90), is expecting too much. The signal can be improved by -3 dB by doubling the power setting at the transmitting radio, e.g., 100 mW increased to 200 mW would improve your signal from -85 to -82. Antennas with increased gain will also help. Say you had the standard 3 dB antenna and changed it for a 12 dB antenna, that's a 9 dB increase, so your signal would increase from -82 to -73 which would be an excellent signal, probably capable of 54 Mbps. Using the term excellent in terms of running a WISP, it would probably be only 3 bars on a 5 bar signal strength meter. Don't worry if, as a WISP your signal quality is low, like 14%. It's not really a problem since -82 is considered acceptable.