The OB van is well equipped with the studio equipment and also the uplink FM transmitter for sending TV signals direct to the concerned satellites for global relay. The van is coupled with a parabolic dish mounted on its roof and capable of sending microwave signals to the satellite for global coverage of the event. Composite video signal is produced in the studio and amplified using voltage pre amplifiers there itself. These amplified signals are sent to the transmitter complex which is a few km away from the studio. High power transmissions may disturb the monitors by overloading, or a high building, a hillock or a suitable location may not be available to set up a high tower ,hence loss in the coaxial cable is more, hence there is a delay.
Hope this helps.