How to calculate the amount of differential cable delay between a four port directional antenna and a single port Omni directional antenna in TCAS II?

I want to select the amount of differential cable delay between the top (4-port directional) antenna and the bottom (1-port Omni-directional) antenna in the TCAS II RBP-7G connector pin.

In the ACSS TCAS II installation manual, there are four options can be selected in the RBP-7G pin, which is only one-time configurable during the installation. They had given 0-51 nsecs, 51-120 nsecs, 120-200 nsecs, 200-350 nsecs.

I know how to calculate differential cable delay between two cables, which is done by subtracting the cable delays of the two cables. But my question is how to calculate differential cable delay between a 4-port (4 cables) top directional antenna and a single port (one cable) Omni directional antenna.

Is it right to calculate the difference between each of the directional port to the Omni directional port (or) we can just sum all the delays of the directional ports and then subtract the total delay of the directional antenna with the Omni directional antenna delay.

• While this is installed on an aircraft, seems like it would be a better question for Electrical Engineering. Commented Oct 10, 2023 at 18:59