It's possible, but the command phrases that are generated using the range feature are necessary so that the speech engine can match what you're saying to a specific predefined phrase.
While you can use dictation without generating command phrase variations, the speech engine will have to guess at what you're saying without any frame of reference, meaning it could be "set frequency 105.5" but equally "set frequency potato horseradish sea anemone".
If you want to try dictation, use a wildcard suffix in the command name("set frequency *"), and the "{CMD_AFTER}" token to get the dictation result, which will include anything recognized after "set frequency".