This program can be used to generate circles which will be overlaid on a map of the United States or a portion thereof. You may chose single or multiple radii from a particular latitude and longitude location, in degrees/minutes/seconds or decimal degrees. With some preliminary work on your part, these can be used to:

• Approximate the protected service and interfering contours for an FM or TV station.
• Show areas which meet the minimum spacing criteria for FM stations, e.g., for allotment studies for FM commercial stations prior to filing a petition for rulemaking.
• Find the location of the blanketing interfering contour (see Section 73.318).

• Plot the locations of AM, FM, and TV stations (or those of other services) with respect to a given set of coordinates.

• Show streets in the vicinity of a station's transmitter site, e.g., within 3.2 km (two miles) of an AM directional station (see Section 73.1692).

• Show the location of your home with respect to the protected service contour of favorite FM or TV stations.

Examples of the map outputs are shown below. The generated maps may be saved as GIF files for future reference (see the Tiger Map Facts by the Census Bureau on how to do this).

It must be noted at the outset that this program will not generate actual service or interfering contours for radio stations. Actual signal strength contours for FM or TV stations are affected by the terrain in a given direction, as well as the irectional pattern (where used) of the broadcast station. Nevertheless, by using circles in lieu of contours, a particular contour of interest may be approximately located. The circle data will be close to the nondirectional contour data over flat terrain, but may be less so in mountainous terrain. Also, actual coverage will usually be less than predicted here if a directional antenna is in use. Please keep these facts in mind when reviewing the map plots generated by this program.

Two items are necessary for this program to work properly: (1) a browser capable of showing frames, and (2) patience. This program employs the Census Bureau's Tiger Mapping Service to generate the map backgrounds. Because the Tiger Map servers are very busy, and due to the large size of the files sent over (over 360 points per circle), it will usually take some minutes to generate a map. This can be reduced (and reliability improved) by using this program during hours when the Tiger Map servers are least busy. As you might expect, this consists mostly of the night and weekend hours. Tests of this program to date show that performance drops off significantly after about 12 Noon Eastern Time, and improves again after about 7 PM Eastern time. Please be advised that this condition is outside the FCC's control. The best advice we can give is to avoid afternoon use of this program as much as possible.

We suggest that you look at the information available at the Census Bureau's Tiger Mapping Service (particularly the FAQ page), so as to get an idea of the capabilities and limitations of this program. Please note that not all options available for the Tiger maps have been implemented in the FCC's map-point-creation program. After sending the initial data, you will have the option of modifying the data to include additional stations or to resize the map. The initial circles will be scaled to fit the map; for additional circles, particularly those at different coordinates, you will probably need to select a new map height/width in degrees.

Before using this program, please confirm the cache on your browser is set to verify documents every time. If your browser is set differently, you may have difficulty using the Map Options to change the initial map.

• For Netscape 3.0, the cache options may be changed by going to
  Options | Network Preferences | Cache => Verify Documents: Every Time.

• For Netscape 4.0, the cache options may be changed by going to
  Edit | Preferences | Advanced (click on the "+") | Cache | Document in cache is compared to document on the network: => Every Time

• For Internet Explorer 4.0, the cache options may be changed by going to
  View | Options | Advanced. Under "Temporary Internet Files", select "Settings" . On the "General"| Check for newer version of stored pages => Every visit to the page

• For Internet Explorer 5.0, the cache options may be changed by going to
  Tools | Internet Options . On the "General" tab, and under "Temporary Internet Files", select "Settings", then | Check for newer version of stored pages => Every visit to the page

Resources you may want to refer to before creating a map include:

• FM Query for the ERP and HAAT of FM stations;

• TV Query for the ERP and HAAT of NTSC (non-digital) TV stations;

• FM and TV Propagations Curves Calculations, to get the radial distance given an ERP and a HAAT for an FM or NTSC TV station;

• FM Station Classes for reference ERPs and HAATs for the various FM station classes;

• Minimum Spacing Requirements for FM Stations;

• Find Community Coordinates program;

• The US Gazetteer, at the Census Bureau at http://www.census.gov/cgi-bin/gazetteer can be used to find coordinates for individual locations, such as your community. The Map Browser at http://tiger.census.gov/cgi-bin/mapbrowse-tbl can then be used to further narrow the coordinates of a particular point such as your home. (Note: this map retrieval method was not used here because the retrieved map cannot easily be resized as needed.) Please be aware that the FCC does not warrant the accuracy of the Census Bureau's data, although as of this time we are not aware of anomalies in that data.

Comments and suggestions may be directed to Dale Bickel, dale.bickel@fcc.gov.