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Zero Span and Full Span for the Spectrum Analyzer

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anurag0504

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Hi,

I would like to know what are zero span and full span for the spectrum analyzer.
I know what a span is but have no clue what happens when we use zero span and full span setting on the Spectrum Analyzer.

Thanks in Advance..

Anurag
 

biff44

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FREQUENCY span.

If zero span, it does not sweep at all but stays at the one center frequency it is set at.

Full span means it sweeps the full available band of the spectrum analyzer. If it is a 1 MHz to 18 GHz spectrum analyzer, that is what it sweeps at.

But...you could not figure this out on your own by pushing some buttons and seeing what happened?
 

keith1200rs

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It may depend on your setup, but on zero span the x axis can be time instead of frequency.

Keith
 

tbui

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biff44 said:
FREQUENCY span.

If zero span, it does not sweep at all but stays at the one center frequency it is set at.

Yes, but it is still sweeping , time sweeping :D
 

keith1200rs

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tbui said:
Yes, but it is still sweeping , time sweeping :D

I think it depends on the spectrum analyser. My R&S time sweeps in zero span but I seem to remember my old HP181 just sits at a single frequency with no x axis movement.

Keith
 

biff44

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So, once again a simple question actually has a complex answer!

Well, I am not familiar with R&S analyzers, but all the analyzers I have worked with stop sweeping and act like a power meter at the ONE frequency it is set at. You can vary the resoluation bandwidth to let in smaller or larger noise bandwidths, but it is essentially a one-frequency power meter. It will ignore any power any significant distance away in frequency.

The purpose is to specifically turn off the sweep function, as the sweep sometimes really screws up the measurement. If you have a pulsed source, if the pulse happens when the sweep is not on that one frequency, it misses the pulse power.
 

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I think I can stop the time sweep on the R&S, but it can be useful to sweep though - for example looking at a pulsed transmission. I think you can also set a threshold dBm like an oscilloscope trigger. It is the FSL3 I have.

Keith
 

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