With the SMC Gateway attached to one radio, the gateway will by default send messages out from the default channel on the radio. But, using the gateway’s relay outputs connected to the radio GPIO pins, you are able to change channels on the radio and thus can send messages over different channels.

Here’s a sample of how to create a flow that lets you send a test message to channel 1/group 1 and channel 2/group 1. The delay is to allow the radio time to process the channel change before we send the message.