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Simple question. Does this UNCORRECTED performance look OK?

Question asked by drkirkby on Jan 9, 2013
Latest reply on Jan 10, 2013 by drkirkby
I've a suspicion my VNA (8720D) might not be working too well at low frequencies (below 500 MHz or so). I'd appreciate clarification if what I observe is correct. 

If I do a factory PRESET of the instrument, join the pair of Agilent 85131F test cables together, I get what is seen in the attached diagram if I plot |S21| in dB. 

I expect the ripples in |S21|, since this is uncorrected, but I'm surprised at the drop off at the low frequencies. Note that |S21| drops to as low as -23.4 dB at 50 MHz, 

Is this normal, or does it indicate a problem? 

PS - Sorry for the poor graph. I'm no Excell wizzard. 


Edited by: drkirkby on Jan 9, 2013 8:26 PM