> One other thing is that some spectrum analyzers aren't really designed > for low noise performance. Since the noise floor is often pretty high, > the design of the whole RF chain (e.g. spur levels and such) might have > assumed that lots of things would be hidden in the grass.
True, it's one of the many selection criterions for selecting the instrument that meets your needs. I've been looking a the luggable HP series 859x and 856x, preferring the latter because they have a PLL YIG whereas the fist uses a free-running oscillator. But these machines are old, 80's and 90's, pricey, and not really THAT good. Add decent range (up to 9GHz to see recent 5.8GHz devices) and a tracking generator and before you know it, you'll be paying $6k or more for a 20 year old instrument. > If the > analyzer is of the recent "bring a band of RF down to an IF, sample and > FFT it for fine resolution" architecture, such things as the number of > bits in the ADC and the "cleanliness" of the sampling clock might have > been chosen based upon doing 1024 point transforms being displayed with > 100dB dynamic range (10dB/div and 10 divisions). Most modern instruments do that, at least to some degree. My R&S goes down to a RBW of 10Hz by just mixing. Additionally RBWs of 5, 3, 2 and 1Hz are achieve by additional FFT. This instrument dates from 2001, but I don't think more recent instruments can achieve a mixing-only RBW of 5Hz or below. > (not to mention the spectrum analyzer actually generating spurious > signals. I ran across that one last year and thought I had an > interference source, but, no, went back and checked the spec sheet and > it said spurious are <-80dBc, and sure enough, there it was at -82 dBc. > And stories about the first LO coming back out through the input are > legion.) Gee, I wish I had consulted this group BEFORE buying my instrument. I'm happy with it and I don't regret anything, but you could have added a lot more arguments in favor or against… _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
