Many coaxial relays have a too low isolation between the ports during the change-over. If the power amplifier (in a transmit-receive system) is switched too early, this may lead to damage or destruction of the input transistor in the preamplifier or converter.
With a sequence controller, this trouble can be avoided. The sequence controller provides a control signal for the coaxial relay and it switches the voltage supply for the power amplifier. There is a time delay between the two signals to guarantee safe switching.
Control circuit for transmit-receive systems which use power amplifiers and coaxial relays