On Fri, 11 Dec 2009 13:58:05 -0800 (PST), Bill W4ZV wrote: >I'm not sure who said 3 dB was the minimum detectable by a listener but I >believe it's incorrect. 1 dB "roughly matched the smallest attenuation >detectable to an average listener".
Yes. I'm a member of the Acoustical Society and work in pro audio, so I've had to learn a LOT about these things. BUT -- that 1 dB that's the smallest change noticable by the average listener for sounds NOT in the presence of noise or other interfering signals. Add some noise that's close in level to the desired signal (or even stronger than the desired signal), and a 1 dB change becomes more obvious. For sounds with NO interfering noise, it takes a change of nearly 10 dB to be perceived as twice (or half) as loud. What really matters in communications circuits is signal to noise ratio. The poorer the signal to noise ratio, a dB or two becomes more important. John said: >Many many times i have just turned down the drive to produce 200 watts and >I have not had one station comment that my signal has dropped. That's because of a combination of two factors 1) Your signal was likely well above the noise 2) the change in LOUDNESS of your signal was eliminated by the AGC in the other guy's RX. I'm a member of a very competitive contest club. Our guys will do a lot to maximize their signals and their RX. I use RG11 to feed dipoles to save a dB of loss. I use hard line for the long run to my SteppIR to save 2 dB. I work to get antennas up a bit higher to get me over the ridge to the east, boosting my signal another dB or two. I have Beverages to hear a bit better. All of these little improvements combine to let me hear about 6dB better and transmit 2- 3dB louder. I recently put up a tower and beam, giving me about 6dB on the higher bands. Each of these changes has contributed a bit, and over tiem, my QSO rates have improved a lot. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
