General Information About
FM and TV Service Contour Maps

Map Display

  • Use the FM or TV Query to retrieve maps. At the FM Query or TV Query search form, enter your search parameters, and select the longer, detailed Query output. When the records are retrieved, look under each record for a series of links. Click on the "Service Area Map" link to retrieve the map page.

  • These maps display the service contour for the FM or TV station that is generally protected from interference caused by other stations under the present FCC rules. However, interference-free reception is not guaranteed at all locations within this contour. Local conditions (for example buildings, terrain, receiver quality, type of receive antenna used) can influence reception of a radio signal.

    Service does not stop at this contour line. In most cases, FM or TV stations can be received at locations well beyond the location of the mapped contour, with interference-free reception becoming less likely at greater distances. As a result, most stations actually provide serve to a substantially greater area than depicted by this contour. However, reception in in areas outside of this service contour is not protected from interference caused by other authorized stations.

  • Contour distances less than 1.5 km: The smallest curve on the FCC's FM and TV propagation curves calculates the contour location at a distance of 1.5 km. For distances which are predicted to be less than 1.5 km using the propagation curves, the curves program uses the free space equation to calculate the distance to the contour. Near 1.5 km, these two methods do not agree: the free space equation calculates a larger distance to the contour than does the FCC's propagation curves. This shows up as an apparent discontinuity or jump in the contour at certain azimuths.

    To minimize the visual effect of this discontinuity on the maps, distances calculated by the free space equation that are in excess of 1.5 km have been set to 1.5 km. This phenomenon will be seen most often on maps for lower-power directional FM or TV translator stations.

  • Terrain affects FM and TV signals: Land features can affect the shape of an FM or TV station's service area. For example, a mountain may truncate service in some directions, reducing the service contour. Or a valley may cause a bulge in the contour because the terrain is lower in that direction, allowing the signal to extend further. FM and TV stations will often locate on a tall tower or mountaintop to reduce the effects of intervening terrain.

  • Maps vary in scale to allow both large and small contours to be displayed with clarity. Maps will not be provided based on one display scale only.

    Use of maps

  • FM and TV Service Contour maps are provided for general use. No restriction is placed on the use of these maps. Any use is at the user's sole risk.

  • The FCC does not guarantee the accuracy of the generated maps. Maps may not correspond to data used by applicants or the staff to evaluate applications.

    Map Generation and Retention

  • We regret that we cannot provide source code or assistance to persons or groups looking to generate their own maps. Nor can we honor requests for special maps or additional service or interfering contours, or computations of area or population within these contours.

  • AM service contour maps are not available, and we have no time frame for providing such maps.

  • Maps are generated from data extracted from the Media Bureau's Consolidated Database System (CDBS). The accuracy of the maps is in part dependent on the accuracy of the data contained in that database.

    Data errors in the FM records may be brought to the attention of Dale Bickel,

    Data errors in the TV records may be brought to the attention of Hossein Hashemzadeh,

  • Maps will not be generated for archived CDBS records. However, maps for current records that later become archived will be retained, at least for the present. Maps for such recently archived records may be removed at some future date without prior notice if circumstances warrant.

  • Map images are generated using the Census Bureau's Tiger Map server ( We thank the Census Bureau for its continued maintenance of this valuable resource.

    Map Image Sources

  • Map files are saved in the following directory:

    Corresponding map scales/legends are saved in the following directory:

    FTP may be used to retrieve map or map scale files.

    A browser can be used to open these directories directory via

    THIS IS A VERY LARGE DIRECTORY (2 GB) and getting a list of files will take some time. Pay attention to the capital letters in these links.

  • Each map consists of two files, the map image itself and a scale image. File names and links are constructed as follows:

    Map Image Service + Application ID number + ".gif"
    Legend or Scale Service + "L" + Application ID number + ".gif"

    where the services correspond to

    FM   TV
    FMFM stationsTVTelevision (analog)
    FXTranslatorTXTranslator / LPTV
    FLLow Power FMCAClass A TV
    FBFM boosterTBTV booster
    FSFM auxiliaryTSTV auxiliary
    DTDigital TV
    DSDigital STA
    DXDigital auxiliary facility