Products > Test Equipment
Zero span spectrum analyzer .FFT, sweep, filters and RBW.
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G0HZU:
I'm unsure what the intended application is, but see below for a screenshot of an old Agilent SA set to zero span in sweep mode. This effectively halts the sweep.

I think this effectively uses a 1Hz (digital) RBW filter at the digital IF. The test signal being fed to the analyser at 451MHz has a regular step change in amplitude and the plot shows the response across a 50 second time frame. Despite the 1Hz RBW filter, it does a reasonable job of displaying the two level states.

Note that unless your DUT and your test gear is locked to a common frequency reference, you may find the signal from the DUT will not be at the same frequency as the analyser. With a 1Hz RBW up at 451MHz with a zero span setting, this would require very accurate and stable frequency references in the DUT and the analyser.

G0HZU:
See below for an amplitude that varies as a triangle wave. Again, the analyser does a reasonable job of displaying what is happening in the time domain when set to zero span with a 1Hz RBW. The triangle shape isn't perfect, but it's fairly close to a triangle shape.
xugmu:
Thanks for the pictures, an old Agilent analyzer with a 1Hz resolution must have been a fairly expensive device.

The purpose of the thread was to find out the difference in the result between using zero span mode in sweep mode or in FFT mode.

The 3000 series from Siglent announces the two modes in its user manual. The 800 series from Owon, afik, does not say anything, and I get the impression that when very low resolutions are used, it uses FFT mode.

I have a TinySA (sweep) that also has zero span mode, the problem is that it is a device limited to a RBW of 200Hz.

On the other hand, I have SDRs that obtain resolutions of 0.2 Hz but use FFT mode, the reduction of the bandwidth in this case I imagine will be achieved with digital filters.With demodulation software, I have reached approximately 400 Hz of bandwidth.

Harmonics and spurious things aside, Afik a swept spectrum analyzer "should not need filters to limit the bandwidth" since its oscillator would be stopped at a frequency and the device would only let that frequency through.
tautech:

--- Quote from: xugmu on August 06, 2024, 09:34:37 pm ---The 3000 series from Siglent announces the two modes in its user manual.

--- End quote ---
:-//
SSA3015X Plus will need your needs.
xugmu:

--- Quote from: tautech on August 06, 2024, 09:46:41 pm ---
--- Quote from: xugmu on August 06, 2024, 09:34:37 pm ---The 3000 series from Siglent announces the two modes in its user manual.

--- End quote ---
:-//
SSA3015X Plus will need your needs.

--- End quote ---

I've read quite a bit about the 3000 series. They would be the perfect devices to solve my question: does zero span mode work better in FFT mode or in sweep mode?

That's why I'm asking here before buying, to know what I'm buying.
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