Hello, I am measuring an a PCB in the over to see insertion loss behavior.
I plugged 1.85 sma connectors on both ends of the trace and started measuring s-params up to 130C.
at first test it ran good i took out the smas and plugged in another PCB and ran test again up to 130C.
on the 4th test I got S-param show me there is open circuit although everything got cooled down and I recalibrated the VNA between each test.
I got into conclusion that the heat ruins the dielectic material in the connector but later I found out there is no dielectic material in the1.85 connector.
What is happening in this situation?
Thanks.

 

The PCB, connector, and fixture all expand differently. At 130 °C, a small shift can reduce or completely lose center-pin contact.

 

few questions:
1. what is the name of this air dielectic connector ? its not sma.
2.how much time i need to wait before recalbrating ,after vna cable hold 125C