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.


Dave Dybas said...

I saw mentioned on another site that AM MW patterns were created on Google Maps using a software program called "Radio Data MW". The other site linked then pointed to Radio-Timetraveller for additional info.

Do you know about this "Radio Data MW" software ? I'm trying to get my hands on something that will do AM MW pattern plots....something cheaper than V-Soft....which is way beyond my pocket book.

I'd like to be able to use the software to see if some AM stations could expand their signal, as other co-channel stations turn in their licenses.


Hi Dave,

Radio Data MW is my program and I use it to create the pattern maps and for general FCC database testing. It is not a free-form pattern generator using varying input, but instead uses the FCC database to generate current patterns, among a lot of other things. I wrote it over a 6 year period from about 2009-2015. It is not published, but a just private effort. It does not have a general ability to tweak data like power level or tower configuration.


Dave Dybas said...

Hi Bill,

Thanks for the response. I've worked a bit with the CDBS and have created my own SQL query program that I use to screen Cell Sites for proximity to AM stations, and to determine if the Cell Tower height falls into the FCC Part 1.30002 AM Compliance specs for the cell industry.

I'm just a little guy looking for a cheap alternative to V-Soft .... :)

Thanks again.