Here is a manual antenna switch for Soft66LC4. The RF input port of the device is connected either to a main antenna or to a dummy load to be grounded.
The main antenna is also connected to IC-7410 all the time, so you must remember to change the switch position before transmitting.
One problem is that the LO of Soft66LC4 is always audible indepedent of the switch position.
A 1kHz tone from Soft66LC4 with its LO at 7020kHz is visible at the upper half of the waterfall showing the audio signal from IC-7410. The switch is momentarily changed to the ground position, the period of which you can observe at the lower half of the waterfall, but the strength of the tone does not change regardless of the switch position.