Network Analyzer measurements problems

Hi there

we are working at our Rf labratory with a 8720ES VNA. recently, we have problem in measurements. This device dosen't recognize its ports. in other hand, its monitor shows some signals, but if we connect the cabels, there is no effect in monitor signal. please help us


Thanks a lot

I don't know your VNA model.
However it could be:

1. the RF power is switched off
2. you are displaying the memory instead the traces
3. you set the instrument to get the inputs from the auxiliary ports (4 pair that normally have to be connected toghther by rigid coaxial cables: check also these connections).
4. The IF coaxial cable that connect IF IN with IF OUT has been removed

Did you try to recall a previously saved state ? Did you try to use the preset button to restore the factory defaults ?
It could also be the input bridge of the instrument has damaged due to excess input power, even if it seems strange that both channels are not working.

Ports might be burned..