Check the maximum signal spec on your transceivers. Usually something up to +10 dBm is considered a safe level. So if your TX power is say + 50 dBm this would imply that switch isolation of at least 40 dB would be required, so you could look for something like 50 dBm isolation just to be extra safe. Please check out my math yourself. I think ARRL uses the figure of +10 dBm as the maximum level they put into a transceiver when they do their testing. Some folks with multiple transceivers and antennas use patch panels which have good isolation, and make accidental mishaps nearly impossible. In commercial installations patch panels are often utilized. Rick KL7CW