Quite right Bill, in an audio laboratory or perhaps in a very quiet telephone circuit.
But radio communications is different according to what I learned in school, lo' these many years past. Over half a century ago most radio communications engineers began using 3 dB (2:1 power ratio) as the minimum change in a signal level that would normally be just discernable to the listener, considering typical band noise and QSB. That was based in actual on-the-air observations by a great many operators over time. When considering changing my power level, I never consider it worthwhile to change less than 3 dB and more typically 6 to 10 dB as the minimum worth bothering with (e.g. shifting from a K2/10 at 10-15 watts CW to a K2/100 was a just worthwhile shift). When I was much younger and more "innocent" I used to scramble for each little watt, exulting in running 30 watts instead of 20 watts from a 6L6, for example, or tweaking my 6146 rig to run 90 instead of 75 watts and feeling sure that made a big difference. It sure seemed to produce more results from calls. But, looking back over logs over time, it was clearly an illusion.. That's when I acquired the sign that still hangs over my desk to remind me that "Believing is Seeing". So I don't argue with people who want to make what is a quantifiable silly choice. Instead I say, "If you want to do it and you believe it's worth it, do it." I'm no different. After all, we humans make most of our choices based on emotion and then we use rational logic to justify the choice. Ron AC7AC -----Original Message----- >From 100 to 150, for 1.7 dB, when Bell Laboratories research (with huge capital investment and telephone maintenance dollars on the line) determined that 3 dB was the signal strength change discernment for most people? 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". (see below) "The decibel originates from methods used to quantify reductions in audio levels in telephone circuits. These losses were originally measured in units of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of power over a 1 mile (approximately 1.6 km) length of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz) and roughly matched the smallest attenuation detectable to an average listener. Standard telephone cable was defined as "a cable having uniformly distributed resistances of 88 ohms per loop mile and uniformly distributed shunt capacitance of .054 microfarad per mile" (approximately 19 gauge)." http://en.wikipedia.org/wiki/Decibel#History 73, Bill ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
