Thursday, June 9, 2016

FCC Providing AM Daytime Contour Maps

Not sure it's been mentioned on the forums before, but the FCC's AM broadcast query now includes links showing a daytime groundwave contour map for each station in the database. These, super-imposed over either a Bing-based map or USGS map or Google Earth. Links for pure KML coordinates are also provided for those wanting to map their own.

Only daytime groundwave contours are provided, out to the 2.0 mV/m and 0.5 mV/m contours.

Go to the AM Query page:

Type in a call sign, like KFI (640 KHz, Los Angeles), hit enter, and on the next page shown, click on the station call sign of interest.

The facility record of KFI:

Look for the following links at the bottom of the daytime record:

      Daytime Groundwave 0.5 mV/m Service (and 2.0 mV/m) contours on Bing map
      Daytime Groundwave 0.5 mV/m Service (and 2.0 mV/m) contours on Open Street or USGS Maps
      KML / Google Earth (0.5 mV/m Daytime Groundwave Service and 2.0 mV/m contours)
      Text file for KML-capable browsers

Click on one of the map links and a contour map will be shown.

This is a nice innovation by the FCC. Hopefully, skywave plots will be implemented next.

FCC's contour map for KFI-640


Wisconsin Frank said...

I doubt the FCC will be providing nighttime skywave coverage maps for AM stations as most don't have one, at least officially. The only stations that have a recognized and protected nighttime service contour are the old clear channel stations. At night on the regional channels, the service contour is "limited" by the amount of interference that is caused co-channel. Although new stations have to protect existing stations, there is no requirement for existing stations to protect new stations at night. This can result in some seriously degraded nighttime coverages. I can't remember the frequencies or call signs, but there is a station on the east coast that has a 5kW station pointing it's nighttime pattern right down the throat of the newer station. The nighttime limited contour turned out to be almost 50mV/m! I'm sure a critical listener could hear the older station under the audio of the new station.

I used to work for the FCC in Washington DC in the AM branch and processed applications all day. I also worked for a consulting firm for a while and then came back to the FCC field office in St. Paul MN where I spent nearly 30 years. I have been an avid AM listener since high school and there are few nights when I don't tune in WLS or some other clear channel station.


Hi Wisconsin Frank,

Interesting comments, thank you for contributing. Yes, you are probably right, the FCC will likely not publish nighttime skywave maps any time soon, if ever. My maps are mainly meant for the AM DXer, to see what the possibilities might be. I bet your work at the FCC was interesting.