AnsweredAssumed Answered

Is this FieldFox faulty?

Question asked by drkirkby on Dec 24, 2013
Latest reply on Jan 7, 2014 by theamberco
A friend has bought a used N9912A 

* S/N US48310198
* Firmware A.03.06
* Firmware build 2009-03-31 14.54 
* Seems to have been calibrated/verification ?? by "PLLB Elettronica" I've no idea of the date, as there is no cal sticker. 

Options are: 

106 6 GHz cable and antenna analyzer
110 Transmission measurement
111 QuickCal
231 6 GHz spectrum analyzer
235 Preamp for spectrum analyzer
302 External USB support
303 Network analyzer capability
308 Vector voltmeter

He wants me to look at before sending on to him. I know the firmware is old, but I don't wish to update it yet, since this might be returned to the seller. 

I've only played with the N9912A a little but I used to own an N9923A, so have met a FieldFox before. 

Something strikes me as very odd either using network analyzer (NA) mode, or cable and antenna tester (CAT) mode. Both show bizare results. 

Just switching on, and not doing any sort of cal, I believe it should use the CalReady. With a short bit of coax with N connectors each end, I see: 

* S21 showing a peak +1.88 dB at 751.750 MHz
* S21 showing a minimum of -8.40 dB at 2671.11 MHz

See attached photo I look from the screen. 

This does not make any sense to me. 

To check things best I could, I 

1) Used a 12 lb in torque wrench to get the torque on the connectors right
2) Changed the cable. 

but it does not change the result. I've *not* tried a mechanical cal kit or the fitted QuickCal option. But I'm suspicious if CalReady is so far off, then there is a fault of some sort. I might be able to "hide" this fault by calibration, but it does not solve the basic problem. 

Any thoughts? Does this look odd, given there is only a short high quality cables between the two test ports?