On 5/16/2011 12:50 AM, Ian White GM3SEK wrote: > However, the increase in vertical (time) resolution should be even more > dramatic.
Thanks to Heisenberg's uncertainty principle, the product of the frequency resolution and the time resolution of ANY measurement is unity. The frequency resolution in Hz Fr is 1/Tr, the time resolution in seconds. Tr = 1/Fr. Fr and Tr are established by the FFT parameters, and further modified by the filter parameters. The display cannot improve on what the FFT has produced. Another way of saying it is that we cannot know infinitely about frequency AND time in any given measurement. If we want high precision of frequency (and bandwidth of a signal) we must sacrifice accuracy of WHEN the signal was on that frequency. In the world where I have worked professionally for 40 years, we bumped up against this around 1980 when we began using Time Delay Spectrometry (a measurement system that uses a swept oscillator and a swept detector and an FFT to display the result), to measure audio systems, equipment, transducers, and room acoustics. The uncertainty principle applies no matter HOW the measurement was made -- swept or FFT or some guy staring at a meter. In the case of swept measurements, resolution is determined by the sweep rate and the bandwidth of the detector. 73, Jim Brown K9YC ______________________________________________________________ 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
