Tuesday, August 17, 2010

Radio Station Databases 101

Let's explore the details of some of the governmental mediumwave station databases available to us. Much information is there for the taking if you can extract it. But where do we find it? And how do we do that?


Although the FCC's AM Query provides a usable output of AM radio station information, the entire story is not told. Much technical information is left out, particularly field strength, tower, and other engineering data, information which can be found by digging deeper into the actual FCC database files. AM Query is simply a mechanism that extracts predetermined data from the real database, hidden in numerous files in the cellars of the FCC web site. These files are found in the FCC's Consolidated Database System (CDBS) electronic filing system. This database contains some very interesting and useful data.

CDBS file index via http site
CDBS file index via ftp site

I wanted more information than the FCC's AM Query could deliver. CDBS files document in detail the AM, FM, and TV (including digital) services, right down to measured signal strengths and distance between towers. Being an old programming hand for many years, some time ago the idea occurred to me to write a program which would use these files as input and provide a varied display of interesting and useful station data. My Radio Data MW program was born, and has become a sort of sideline hobby for me ever since. If I ever get it to a distributable state, I may one day publish it.

For the enthusiast or budding programmer wanting to extract information out of these files, where does he or she begin? Actually, once unzipped, all of these files are simple text files which can be opened in any text editor. My choice for a text editor in recent years has been Notepad++. It is an excellent freeware editor, useful not only for text files but also programming and scripting.

Okay, now that we have our text editor/viewer, how and where does one begin to gather information on mediumwave stations? From the CDBS database, here are the FCC files which must necessarily be examined. The pertinent information in each file is described. Be careful to note that these FCC files cover all services: AM, FM, and TV, including Traveler's Information Services.

The facility file, (facility.dat)
This is the key file for unlocking all the others. There is one record here for each facility (station). The facility ID number within each record will eventually lead you to the rest. Keep it handy.

Information found in this file:

* The station's facility ID
* The station's service community city, state, and country
* The station's call sign
* The station's frequency
* The station's current licensing status
* The station's digital status (IBOC or not)

The engineering index file, (am_eng_data.dat)
Multiple records usually exist for each facility. The application ID in each record points you to the station's antenna system record in am_ant_sys.dat. Keep this handy too.

Information found in this file:

* Cross reference back to facility ID
* The station's class (A, B, C, D, or unknown)
* The FCC application ID (an identifying number)

The application file, (application.dat)
This file contains a historical list of all applications filed by every station in the FCC database. It is a huge file, some 60MB.

Information found in this file:

* Cross reference back to facility ID
* The FCC application ID with cross reference to the more commonly known application resource number (BL-19990713DC)
* A secondary call sign reference (can be an old or new call sign)
* A secondary frequency reference (can be an old or new frequency)

The antenna system file, (am_ant_sys.dat)
Multiple records usually exist for each facility. An individual record exists for each service a station is authorized to use (Unlimited, Daytime, Nighttime, Critical Hours), and multiples of these may even exist. In this file we get to the heart of the station's information.

Information found in this file:

* Cross reference back to application ID
* The station's antenna system ID
* Number of augmentations to the signal pattern
* Hours of operation (its service: Unlimited, Daytime, Nighttime, Critical Hours)
* The station's latitude (tower site coordinates)
* The station's longitude (tower site coordinates)
* The station's power for this service
* RMS signal strengths at 1 kilometer in three varieties
* The station's domestic licensing status
* Number of towers
* Antenna mode (DA2, ND1, etc.)
* Indicator showing if record is current or archived (important)

With a station's latitude and longitude, using proper programming it is possible to calculate its distance and bearing from your home location. It is also possible to calculate the sunrise and sunset times at the distant transmitter. Using the station power and/or measured signal strengths at 1 kilometer, and knowing the distance you are from the transmitter, the path loss and a rough relative received signal strength can be calculated for daytime reception of stations within a few hundred miles of your home location. Of course nighttime, with its enhanced signal propagation and atmospheric conditions, would preclude any calculated value.

The towers file, (am_towers.dat)
In short, this file contains everything you need to calculate a station antenna's broadcast pattern. You can also plot tower positioning. A record exists for each tower in a station's tower array.

Information found in this file:

* Cross reference back to antenna system ID
* Antenna system resource number (ASRN - FAA number)
* Tower height, measured in various ways
* Top load switch (tower type: 0, 1, 2, 3, etc.)
* Signal field strengths
* Relative tower positioning
* Tower spacing
* Tower phasing

AM broadcast station signal pattern graphs are calculated through a rather complicated formula. A description of this and other formulas can be found at:

Directional Antenna Systems
Modification of directional antenna data

An excellent treatise on using these formulas can be found at:

A Modern Method Of Predicting AM Tower Vertical Radiation

The augmentations file, (am_augs.dat)
This file documents the augmentations to the station's signal pattern. Multiple records can exist for each facility if augmentations are used. Radio station signal patterns are sometimes further modified at the tower site by what are called "augmentations". Augmentations are modifications to the standard broadcast signal pattern, usually to further null the signal strength in a certain direction to bring it into FCC "signal contour" compliance.

Information found in this file:

* Cross reference back to antenna system ID
* Azimuth of augmentation
* Span (in degrees) of augmentation
* Radiation strength of augmentation

Using this information, we can further refine a generated graph of the station's signal pattern.

The facility index, (fac_party.dat)
This file is a simple cross reference of facility ID to owner information in the party.dat file.

Information found in this file:

* Cross reference back to facility ID
* Index forward to party ID (for owner information)

The owner information file, (party.dat)
A huge file of all kinds of owner information.

Information found in this file:

* Owner names and addresses indexed by party ID

And finally, to decode what all the above files mean, be sure to examine:

Code Table
Engineering Data Description (PDF)


Counting Licensed Stations

Have you ever seen the official FCC licensed station count? Lately the count has been 4786. The FCC uses the facility.dat file to determine this number. In this file, each facility has one line of information. There is a field in each line indicating the station's licensing status. Simply by totaling the number of LICEN (licensed) and LICSL (licensed but silent) entries gives you the licensed count. Total the LICSL entries by themselves, and you have a count of the number of licensed but silent stations.

Counting Digital (IBOC) Stations

Again, the the facility.dat file is used. A single character field in each record contains the letter "H" or "D" if a station is digital. Currently no "D", or purely digital mediumwave stations exist, they are all hybrid ("H") IBOC. Non-digital stations show a blank field. Count the number of "H"s, and you have the IBOC count.

Gathering It All

Combine the facility.dat file information with the engineering data index file information (am_eng_data.dat) and you know the station's class and most recent application ID. Look for this application ID in the antenna system file (am_ant_sys.dat) and you will have the station's position coordinates, hours of operation, and a host of other information. Cross reference the facility ID to the party.dat file and find the owner information. And finally, inspect the am_towers.dat file using the station's antenna system ID for the detailed field strength and tower information. Use the tower information and theoretical field strengths to calculate the antenna broadcast pattern.

Simple, it is not. It is overwhelming at first. The FCC's file layout is not friendly. But a tremendous wealth of information is available to the enthusiast or programmer who wants to work at it.


The FCC database has information on Mexican stations. Use it with caution. The two neighbor countries on our borders, Mexico and Canada, must file with the FCC for every station that wishes to broadcast. We do the same for them. Much of the data within is hopelessly outdated, especially the data for Canada, as Canada continually loses many of its mediumwave stations to the FM service.

The published link for official Mexican government mediumwave data is:


It is a PDF document of all supposed currently licensed and on the air mediumwave stations. All I have ever been able to get out of this link is a "503 - Service Temporarily Unavailable" response.

The next best bet comes from the official Mexican telecommunications site, Cofetel. The only government list I have found available, also in PDF form, is the Infraestructura de Estaciones de Radio AM list. Though the URL address is dated 2008, the actual PDF retrieved is dated 31-Dic-2009, or December 31, 2009, so hopefully the information is somewhat current.

Unfortunately, this station information lacks transmitter latitude and longitude coordinates, and a host of other needed technical information. It might be possible to correlate the Mexican stations with the FCC's database to get this. I haven't put forth the effort yet.


Canada has a nice AM Query of their own, but like the FCC's AM Query, the entire story is not told and much technical information is left out. But we are in luck. It turns out that Canada's AM Query searches a deeper database just like the FCC does, so much of the information is available, though hidden.

The Industry Canada engineering database houses it, with links shown just below.

Industry Canada engineering page
Industry Canada engineering database (

Rather than simple text files, Canada has chosen a dBase file format (.DBF) for its files. Download and unzip and you will have them. Though the records are somewhat textual in nature, they are more like XCEL records and a text editor cannot be used to view them. You must use a specialized viewer in order to look inside.

CDBF for Windows by WhiteTown Software, which used to be available as a shareware DBF viewer/editor/converter, seems now to be purchase only. A demo is available but usable only for a short time. A better choice now is Exportizer, totally free. It also supports conversion of the DBF file to other formats.

Once again we have our text editor/viewer, how and where does one gather information on Canadian mediumwave stations? From the Industry Canada database files, here are the ones which should be examined.

Information found in this file:

General AM station data, like the FCC's facility.dat file.

Information found in this file:

Tower info, like the FCC's am_ant_sys.dat and am_towers.dat files.

Information found in this file:

Description of codes used.

Information found in this file:

Country codes

Information found in this file:

Owner information

Information found in this file:

Signal pattern augmentations, like the FCC's am_augs.dat file.


Combining the Industry Canada information with the FCC's, we now have two countries with a wealth of information about their mediumwave service. If the missing information from Mexico's PDF file can be extracted from the FCC's database (namely the latitude and longitude coordinates of the stations), we can then create a single, comprehensive file with all the station data we need.

See also: Canadian/Mexican AM Station Search

Another country of interest but outside the North American realm is Australia. Under a separate post, Australian Mediumwave Database, I show where to find detailed technical information on Australian mediumwave stations.

The current build of Radio Data MW.


Bigroo said...

Great Site, can you please give the website of where to find Radio Data MW program?

Radio-Timetraveller said...

Thanks Bigroo.

Unfortunately the program isn't available yet, as it is still under development.

I hope to make it available in the next year.

I'll be reporting more on it in this blog.

Bill (Radio-Timetraveller)