Total posts : 45366
Video modulators, as used by cable companies, are available from several sources, and also contain the accompanying audio modulation section. Their power can be set from 0 to 10-Watts, and they work perfectly well into an antenna.
I would then purchase a video black signal generator, I got a Tenma type from MCM, and simply transmit black on the video section.
Another thing to check is whether any wireless mic manufacturers have systems that operate in the range… you could use the transmitter section with a pad for inputting line-level audio.
Be sure to scan your local band to pick the least used channel for your station.