Tektronix WVR7200 Installation And Safety Manual page 26

Basic Installation Procedure
For Monitoring Composite
Signals
Figure 3: Option CPS
Line Termination
20
Connect your sources to the CMPST A or CMPST B loop-through inputs on
the rear-panel.
Your instrument uses passive loop-through, analog reference and composite video
inputs. Accordingly, the loop-through inputs must be terminated externally.
It is important that this external termination meets accuracy and return loss
requirements.
If the instrument is installed to monitor an operating link, the destination receiver
and the connecting cable serve as the termination. This monitoring connection
checks the performance of the entire path. The return loss of the instrument is
sufficiently high that, in most cases, the destination receiver sets the system return
loss.
In cases where the instrument is placed at the end of a link, a BNC termination
must be installed on one side of the loop-through input. The termination must
be 75 Ω and DC coupled (good return loss extends to DC). An appropriate
termination is Tektronix part number 011-0102-00; this is a 75 Ω, End-of-Line
termination.
Return loss from composite signals must be >40 dB from DC to 6 MHz.
WVR7200 Installation and Safety Instructions