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Measuring receiver "Range Hold" for TRFL (need help)

Question asked by Achrononmaster on Feb 10, 2009
Latest reply on Jun 7, 2010 by tabbott
Hi, I'm new to microwave metrology so please bear with me.  I'm using an E4440A PSA with Measuring Receiver personality.

I would like to make relative TRFL measurements (power ratio measurements ultimately for attenuation measurement) and avoid the uncertainty introduced by range change calibrations.  I figure I can use the "Range Hold" option, but I have a number of queries about doing this.

Q1. I see in the user manual that using range changes is somehow "optimal", and in the N5531 PSA Spec. Guide it seems to suggest, but does not appear explicit, that the linearity is not so good in range 3 (lower power) than range 2 and linearity is best in range 1?  Is that a correct interpretation?

Q2. If so, how can I determine the linearity uncertainty when/if I use Range Hold?  Is it likely to be a larger uncertainty component in power ratio measurements than the uncertainty associated with normal range change operation?

Q3. In either case I still need to determine the receiver linearity.  There is a canned formula in the Spec. Guide but I'm not sure that it applies if I'm going to use Range Hold (indeed I suspect it is not valid when Range Hold=ON).  If so then how should I determine or measure the linearity, do I need a precision calibrated step attenuator for this purpose as explained in the Measuring Receiver User Guide (June 2008, p.383) linearity verification section?

Q4. What other disadvantages are there in holding the range fixed at say Range-1 for low power measurements?  eg., it is unclear to me after reading the documentation whether there is a risk of cooking some internal components (mixer?) of the PSA if I introduce a large signal while in Range 1 on "Range Hold=ON"?  Does the PSA have a failsafe that protects it's sensitive elements, or do I need to be extra careful when using Range Hold, if so how careful, eg., what would be the maximum signal level acceptable with such settings?