All,I agree. 3db is quite easily heard when I switch 3db in and out on my step attenuator.Laryn K8TVZ Neil J pretty much nailed this one: It is generally accepted industry practice for path reliability projection, e.g. Motorola Coverage Acceptance Standards, that 4dB C/N is the point at which an FM communications receiver delivers 12 dB SINAD and that 7 dB C/N is the point at which such a receiver delivers 20 dB quieting. Hence, it follows that a 3dB change in transmitter power [or increase in antenna gain OR reduction of path loss] which will result in a corresponding 3 dB improvement of received C/N would be sufficient to: A] take a received signal from 1 dB C/N [unreadable] to 12 dB SINAD. -OR- B] Take a received signal from 12 dB SINAD to 20 dB quieting - a very noticeable audible improvement in DAQ [Delivered Audio Quality] - a metric that has been used extensively in radio coverage prediction and verification. And this consideration by Roger is technically why 3 dB makes a big difference: The quieting curve of an FM receiver is very non-linear. 3 db will make a very noticeable difference if the signal is well into the noise, barely any or none at all if it's strong. Roger Grady K9OPO I choose to use 250 watts instead of 110 (roughly 3 dB) on my KQ3M repeater in Hay's Mill PA. I can tell you that 3 dB makes a big difference, in both the coverage and the electric bill. Believe me, if it didn't, I wouldn't pay the extra money each month. I hope this wraps this thread up... Thanks, Kevin Custer Yahoo! Groups Links
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