From: "Herb Chong" <[EMAIL PROTECTED]> > i'm an engineer who got sidetracked into software early.
Howdy Herb, I'm an engineer also. >From '72 to '76, I worked designing "communications systems" for NSA. >From '76 to 80, I worked for the Secretary of the Air Force, Special Projects specifying and monitoring the development of experimental space qualified communications components. >From '80 to '90, I worked Dan Golden (before he was director of NASA) at then TRW Space Systems Group where I was the lead spacecraft engineer for a number of projects such as the initial concept of the 30/20 GHz program before it was renamed the Advanced Communications Technology Satellite (ACTS) http://acts.grc.nasa.gov/ There were many other programs and projects, but I can't discuss them. >From '90 to '94, I worked for Teletrac corporation as a senior systems engineer. http://www.teletrac.net/ >From '94 to '96, I worked for LCC Corporation, http://www.lcc.com/home.htm and performed for them mostly as a consultant to Clearnet (now Telus, http://www.telusmobility.com/) in Pickering, Ontario, Canada. Despite growing up in Quebec & Vermont, I couldn't take the cold. >From '96 to present I've been working for Technocom Corporation as Principle Systems Engineer. http://www.technocom-wireless.com/. This is where I got sidetracked into software. http://www.technocom-wireless.com/prodLocatePredict.html is one of my patents. > signal to noise ratio is the noise floor below some reference level. Well, Herb, we consider signal to noise ratio to be S/N, where S is the signal power and N is the noise power. If expressed in, say dBm, then it would be S - N (in dB - no units). Now, a minimum S/N may be specified for a given performance specification on some equipments. This would usually be the reference level for the rest of the specifications. > headroom has been the amount above that reference level where something breaks. For us, headroom is the amount of excess power an amplifier can deliver for _short_ durations to reproduce sound (musical or otherwise) without significant distortion. This is different from the continuous power output rating and is usually a function of power supply design among other things. We do not design equipment that breaks itself. Equipment dynamic range (for us) is the difference between maximum power output and and noise power minus a minimum signal to noise. (The minimum sound level is not very useful is it can't be clearly distinguished over the noise.) > time variation has nothing to do with the definition. No, but it's implied. If there were no variation, there would be no need for range, dynamic or otherwise. The sound varies in level with (guess what) time. That is, for example, music is dynamic! Meaning changing, with what? Time! It cannot be predicted by the amplifier. This is why the range is necessary, and why we call it dynamic. If it did not change with time, we would call it static range! When we say dynamic range, we mean the range is provided to accommodate the dynamic (not static) nature of the music (or other sound). Regards, Bob... ---------------------------------------------------------------- They call it PMS because Mad Cow Disease was already taken. From: "Herb Chong" [EMAIL PROTECTED] > i'm an engineer who got sidetracked into software early. signal to noise > ratio is the noise floor below some reference level. headroom has been the > amount above that reference level where something breaks. the sum is the > dynamic range. that is the same definition used by NASA for specifying the > imaging sensors in the Hubble and James Webb Space telescopes. time > variation has nothing to do with the definition. > > From: "Bob Blakely" <[EMAIL PROTECTED]> > > > I have no idea what your background is, but if you are educated in this > area > > , and it will help you, speak to me as though I was an engineer with about > > 30 years experience in this and related areas, because I am.
