R&S FSH-Z2 VSWR bridge strange frequency response?

[Marcel]

Hello,

I have 2 R&S return loss bridges type numbers FSH-Z2 and a ZRB-2.
The directivity of the FSH-Z2 bridge has a strange frequency response comparerd to the ZBR-2.
Both bridges are terminated with a R&S Z-30 reference load.

The attached photo speak for themselves.

Is there optionally a solution or is this normal voor this type of bridge? (FSH-Z2)

Regards,
Marcel

[Marcel]

The photo of my previous posting is a screenshot of the FSH-Z2 and this is a photo of a screenshot from the RS ZRB-2 bridge.

[KJDS]

The spec of the FSH-Z2 is typ 30dB from 20MHz to 3GHz, therefore it's what I'd expect.