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VNA stability test

Question asked by feichen on Feb 24, 2016
Latest reply on Feb 25, 2016 by bar28
Can any one help me?
Our model is E5247A. I want to test the stability of my VNA over time.  The VNA already warms up, at least 3hours. The following is my setup-parameter.
1. 15dBm source power
2.1.5KHz resolution BW
3.Span 60MHz, center at 2.06GHz
4.6401 sweep points
5.Full 2 port Cal

What i did :
connect two VNA port together with Bullet Adapter. And storage S21 (the data) to memory, show the memory-data. At the beginning, the difference between memory and data is around -80dB. 2hour later,  the difference increases to -50 or -55dB(even -45dB), meaning VNA drift a lot. 

But I repeated the same process, but connect two VNA port together with 45dB attenuator. And storage S21 (the data) to memory, show the memory-data. At the beginning, the difference between memory and data is around -110dB. 2hour later,  the difference increases to around -90dB.

I was wondering, is this formal? Why VNA drift a lot with Bullet Adapter compared with 45dB attenuator test?


Thanks in advance.  

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