Travelling radio station

Here is another item I found in the Riverside Daily Press. This 1927 article talks about radio station 6XBR, the "travelling broadcast station of Warner Brothers" (see the truck pictured above), which was to visit Riverside and broadcast live from the sight of a motion picture production (featuring Patsy Ruth Miller and others). In my research, I've come across references to other early radio broadcasts from Hollywood. I wonder if any records exist of such programs? And if the programs themselves still exist ? I wonder if Louise Brooks ever appeared on radio in the 1920's or early 1930's? Any radio buffs out there familiar with these earliest days of radio ?