For curiousity I visited the Prometheus website, which helps people apply for LPFM licenses, and their sophisticated search tool told me that 92.9 mHz is available in my location and even presented a contour map showing the coverage area that would be achieved. What caught my attention was mention that the outer ring of the circle showed the "60dBu Contour."
Inspired, I next visited radio-locator and looked at coverage maps for several stations, noting that three rings are shown, including "local (60dBu)", "distant (50dBu)" and "fringe (40dBu)."
"Hey," I thought. "My TECSUN reads dBu, as does the "Compliance Appliance radio from I.S.S."
That's why today I will be drawing contour maps for all my Part 15 stations showing the local, distant and fringe rings.
A bit of labor for Labor Day.