The FCC

Get Coordinated!

Filing Your Application?
Get your coordinates!

Geographic Coordinates

Do not use the FCC "co-ordinate locator. " That will tell you the co-ordinates of the center of your town. This can be helpful for checking the general radio environment of your area, but the availability of a license at your location is a whole 'nother issue. Do not enter those co-ordinates as if they are yours, or your application will be rejected! You need the co-ordinates of your proposed antenna site.

This website will give you much more accurate geographic coordinates than using the FCC site.

[http://www.geocode.com/scripts/eagle/eagle.pl?cmd=td_i]

(If that does not work, go to www.geocode.com Then go to "test drive eagle geocoding" it will get you to the same place)

Enter the street address of your proposed site and it will give you the coordinates in both decimal degrees and degrees/minutes/seconds, using the NAD-27 standard required by the FCC.

You need to copy down the degree minute seconds co-ordinates. These coordinates can then be entered in the FCC Channel Finder to determine if a frequency is available for this location.

Using the FCC's Channel Finder

The FCC's Channel Finder is at [www.fcc.gov/mmb/asd/lpfm/lpfm_channel_finder.html]

What if my frequency and site are not available?

If there is a frequency available at your proposed antenna location-congratulations!

Now scroll down the page and have the channel finder draw you a "Tiger Census" map of the predicted coverage. This process can give you a sense of what parts of your area have open frequencies.

It is important to remember that these maps are very approximate in nature. The program will draw a circle that is exactly 5.6 kilometers in radius around that point. This is the radius within which just about any radio receiver, in any reception condition, should be able to pick up your station. Some receivers (especially the radios in cars, home stereo systems, and radios with external antennas) will pick the station up to two, three or four times further than this "predicted coverage." Some (like Walkmans, and some clock radios) may not even pick you up at the outer edges of your "predicted coverage.

A word about antenna height Obviously, the height of the location that you build your transmitter on is important. If you have a choice, get the antenna up as high as possible. It should be noted that while not optimal, perfectly adequate coverage can be gotten from a twenty or thirty foot antenna located on a residential rooftop, all other things being equal. Depending on the antenna you choose, It can look less obtrusive than even a standard TV reception aerial. A word about location Also keep in mind: While it is best and cheapest to have your studio and transmitter at the same site, nothing needs to be at the transmitter site except for the transmitter, electric power, the antenna, and some sort of receiver for broadcast audio- either via telephone lines or by radio link. This will add to your costs, but we are currently researching options that are as cheap as $500-$1000 for accomplishing this goal. This way, your studio can be at the most convenient location, and your transmitter can be a relatively unobtrusive appliance in someone's attic. Your average hundred watt transmitter is a little bigger than a breadbox, and can be stuck on a shelf near a regular electrical outlet.

Try to find a location near one of those "good co-ordinates," then repeat the process of checking that place with the geocode site and then the channel finder. This can actually be quite fun when you get the hang of it, like throwing darts at a map to find where your radio station can be.

We are happy to help you do this over the phone or to double check your work.

Filling in the Tech Box on a form 318

Once you have found the correct site for your transmitter, you will be ready to fill out the "Tech Box" on your application. Get a copy of the form 318 here. http://www.fcc.gov/Forms/Form318/318.pdf

Remember that you can no longer file on paper for a low power FM license. You must file at this location: [http://
svartifoss.fcc.gov:8080/prod/cdbs/forms/prod/cdbs_ef.htm]

You can also determine your elevation using the following website: [http://www.topozone.com]

Enter the same geographic coordinates, and this site will generate on screen the correct U.S.G.S. topographical map for the location entered.

The maps on this site are very detailed graphically, so they may take some time to download based on how fast your internet connection is.

At the top left of the map page are several scales - select 1:25,000, which will give you the most resolution.

At the top right, there are three choices for size - select Large.

What will then appear on your screen will be the section of the map with your exact location, in the largest magnification.

The maps include major geographic features, such as mountains, lakes, rivers, hills, etc. and major man-made features such as airports, hospitals, cemeteries, parks, railroad lines, and significant buildings, streets and highways. At this scale, most of these features should be legible. Natural areas are green; developed areas are pink; water features are blue; and new buildings or constructions are generally shown in purple.

If you look closely, you will also see a series of brown contour lines that snake across the maps in irregular but roughly parallel patterns. These lines follow the features of the terrain, and they indicate changes in elevation every 10 or 20 feet, depending on the map. Where the elevation rises steeply they will be close together, and where the ground is flatter, they will be spaced farther apart.

Questions Five and Six

If you follow any one of these lines, at some point you will see the line broken by a number that is a multiple of 10. This number indicates the ground elevation, or height above mean sea level, for that contour. With a good pair of eyes (or a large screen monitor) you should be able to find your address and match it up with the nearest contour line. If you are between contour lines, you should interpolate as bast you can. If it is all too blurry, you may have better luck with a printed map, which should be available at a public library.

The answer you get here will be for question 5 in the tech box: "antenna location site elevation above mean sea level." For the answer to question 6, Add the height of your building and then add the height of any pole, tower or other antenna support that will go on the roof.

A tried and true standard is a 36 foot telescoping antenna mast from radio shack- total cost of a do-it-yourself mast installation between $200 and $400. Convert the feet into meters. Do not use the HAAT calculator on the FCC webpage- this is a whole different thing.

Question Seven

The answer to question 7 depends upon what kind of antenna you want to use. You must give this quantity to the nearest meter. Roughly speaking, it is either:

a) 1 meter higher than the answer to question 6 if you are going to use a 5/8 ground plane antenna- About $110, vertically polarized, good for car reception- but you will have to lower your amplifier power to about 50 watts

b) 1 meter lower if you use a simple dipole. You can use the full 100 watts, and the antenna has no gain. You will probably want it horizontally polarized. It will probably not carry as far with the car receivers as the 5/8 groundplane. It has the advantage of being located a bit below the top of the pole, so if lightning strikes, the surge is more likely to travel down to ground through the mast, rather than through your transmitter. Costs about $100

c) more ambitiously, you can get two circularly polarized antennas. These cost about $400 apiece., plus some more in weird hardware and connectors and such. This is the best kind of antenna, especially for city conditions. It may need a more sturdy tower than just a pole. You will be able to use the full hundred watts. If you use this type of antenna, your answer to question 7, height of antenna radiation center above ground level, should be about 2 meters lower than the top of your tower, or halfway between the connection points of the two antennas, which must be one wavelength apart (about 11 feet). A good budget for this sort of antenna is probably $2000-$2500

The Fantastic New
Engineering Powers of Prometheus

Prometheus has developed software that has given us fantastic new powers to search a metropolitan area for sites that have available frequencies. this software will be able to look at previously unscrutinized nooks and crannies of your town. Our new searching capabilities will not be on par with those of a broadcast engineer, but they are much better than just using the FCC channel finder.

First try the procedure that we describe in http://www.prometheus.tao.ca/fcc.shtml If you don't find anything, contact us to pore over your neck of the woods if you can't find a channel for yourself.

[Take Action] [About Prometheus] [Background and Resources]
[FCC News and Rules] [Links] [Press Center] [Prometheus Home]
Contact us at:
Prometheus Radio Project
P.O. Box 42158
Philadelphia PA 19101
info@prometheusradio.org
(215)727-9620