The PTP 820i with RFU-A 1+1 Hot Standby with Spatial Diversity (Standard) is the "standard" receive space diversity configuration.
There are two antennas at each end of the link: the transmitters share the top antenna, and the receivers each have their own antenna (main receiver at the top, and diversity receiver at the bottom).
For the 1+1 Hot Standby with Spatial Diversity (Standard), the RFU-A Installation Guide states,
"On the rear side, disconnect the left connector from both chassis.
Connect the cable from the bottom chassis to the left connector in the upper chassis.
Attach the loose cable on the bottom to the chassis using a zip tie."
What on earth is going on here?
What are those two RF cables?
Why is the upper RF cable left to dangle in the pleasant telecomm shack's air conditioned breeze?
Please see the excerpts from the RFU-A Installation Guide below:
Please see the slide below:
Note the following:
1. The top branching drawer is a 1+1 branching drawer, whereas the bottom branching drawer is a 1+0 branching drawer.
Do you see the difference?
The 1+1 drawer has RF switches, but the 1+0 drawer does not.
2. When you move the upper cable and zip tie it to the chassis, you are disconnecting the Rx RF switch port.
I've noted the RFU-A transceiver ports Tx and Rx in red; the two left-most ports (upper and lower) are Rx ports.
3. When you move the lower cable and connect it to the upper left port, you are connecting the Diversity Antenna to the Diversity Receiver.
I hope this helps!