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Calibration Problem (Positive S-parameter)

Question asked by xavier on Mar 20, 2011
Latest reply on Mar 29, 2011 by xavier
Dear All;
I had been trying to remotely control an ENA 5071A through a PC, which I managed successfully, but I am afraid that I might have accidently deleted / corrupted some of the ENA calibration file/settings in the process.   The problem I have is that the ENA seems somehow to measure positive (>0db) S-parameter value, for week I have been trying to solve this problem without any success.  I would much appreciate your help.
We have available a 4port ECal kit, the “N4431 – 60004” 300 KHz – 9GHz.
When the ENA is switched on it goes into a state that the calibration Correction setting is “ON” and the displayed S11 parameter is >0db within the frequency band (Fig.-1) . If I set the Correction setting to “OFF” the S-parameter is <= 0db as in Fig.-2 .   I came to a conclusion (might be wrong) that there is something wrong with the calibrated data/setting on the ENA.
I have then connected 4 short SMA cables to port 1-4 respectively and use the above ECal Kit for calibration. The calibrated S parameter (on Fig. -3) on all port still show positive value at some frequency. 
I wonder what might be causing it.  I am concerned as I soon need to perform some channel sounding measurement and with analyser operating this way the results am afraid will inaccurate. 

Thank you all in advance for your help.