Mike wrote:
When using a spectrum analyzer to examine the output of a frequency standard, what are the minimum specification needed? Bandwidth, resolution, sensitivity, etc?
It very much depends on what you hope to see with it. That said, virtually no SA will do anything useful in this application without a fair amount of preprocessing. SA front ends do not have the dynamic range to handle the fundamental frequency and resolve any useful detail down at the oscillator noise level. You will generally need to both filter out the fundamental with a very sharp filter and also use a very narrow SA bandwidth -- less than 1Hz -- to analyze the residue. You may also need an ultra-low-noise amplifier to get the residual noise above the SA input noise.
The HP 3561A "dynamic signal analyzer" is supplied as part of the HP 3048A phase noise measurement system, and has usable bandwidths down to the uHz range. It is arguably the most useful SA for analyzing oscillators. However, it only handles frequencies up to 115kHz, so it needs the rest of the 3048A to be useful -- or at least an offset oscillator (better than the one you are testing) and mixer to heterodyne the oscillator you are testing down to the useful range of the instrument, plus a sharp filter to attenuate the carrier.
Personally, I have rarely needed resolution bandwidths larger than 300Hz for laboratory work (field work is different), and I frequently want RBWs considerably smaller than 1Hz. I can highly recommend the HP 3588A, which operates in both sweep mode and also in FFT mode.
A tracking generator is nearly indispensable for much of what you will (probably) eventually do with an SA, so try to hold out for one with this feature.
Pay attention to ergonomics -- suffering with an SA that doesn't think like you do will drive you crazy. For example, I prefer HP/Agilent SAs over Tek SAs because the HPs allow you to specify a start and stop frequency *or* a center frequency and span, while the Teks only allow you to specify a center frequency and span.
Also personally, I wouldn't waste money on any of the new plastic SAs that are flooding the market, or on any USB SA. I would stick with used HP and Tek instruments (and *possibly* one or two others).
You can find operator's manuals (and service manuals) for the HP and Tek instruments on-line. Study them carefully to figure out which ones have the features and ergonomics you want. You will also pick up information that allows you to ask sellers detailed questions to increase the probability you will get a working unit.
I am all for having one or several SAs around the lab, but I fear that an SA may not be very useful for the particular tasks you are hoping it will perform.
Best regards, Charles _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
