This information and style is no longer current, but here for informational purposes.

More explanations:

Frequency / Channel

In the US, stations are assigned to frequencies by the FCC. The stations are separated by 200 kHz, and end with an odd number. Our FM broadcast band extends from 87.9 to 107.9 MHz. 87.9 is not assigned, except to a few experimental stations. Is isn't assigned because of the proximity to TV channel 6's audio carrier, which falls at 87.75 MHz, and can be received on many FM radios. Other parts of the world have different FM bands. In Japan, for example, the FM band ranges from 76-92 MHz. Some countries also space their stations differently. In Hungary you might find a station on 86.2 MHz! For AM, stations are assigned by the FCC and are all 10 kHz apart. Our AM band runs from 540 to 1700 kHz. Some countries, including Canada, assign stations to 530 kHz. In the rest of the world, AM stations are spaced 9 kHz apart.

Call Sign

The call sign of a station is assigned by the FCC. Like frequencies, a station can request a specific call sign, if it is available. Generally,  stations west of the Mississippi River begin with K- call signs, and stations east of the River begin with W- call signs. Some very old stations, like KYW in Philadelphia, were allowed to keep their old calls after the east/west standardization began.

City of License

The city of license is determined by the station when it submits an application. A city nearby the transmitter is picked usually. Of course, as with WOWC-FM, licensed to Jasper, a station may serve another market, in this case Birmingham. A station must pick a city within it's protected contour as it's city of license. I don't know why.

Power

FM stations in the US are limited to a maximum of 100,000 watts. AM stations are limited to 50,000 watts. Television is a little more complex. Channels 2-6 are limited to 100,000 watts, 7-13 are limited to 316,000 watts, and 14-69 are limited to 5,000,000 watts! Stations with unusually high antennas are often restricted to lesser power levels. FM translators are limited to 250 watts. I am not sure what the limit is on TV translators. A few FM stations are granted "grandfather status", which means they are allowed to operate at higher power levels than current FCC standards allow. WBCT in Grand Rapids, MI has 300,000 grandfathered watts! Even with only an antenna at 500 or so foot HAAT, they still have quite a coverage area.

HAAT

Height Above Average terrain differs from height AMSL, or above sea level. HAAT more accurately reflects the overall "height advantage" an antenna has over surrounding terrain.  So while an antenna may be 1,500 feet up on a tower, it could still have a HAAT of perhaps only 600 feet, if the surrounding terrain is very hilly and the tower is in a valley.

Format / Network

There are countless ways to identify a station. You might hear a "soft rock" station or a "lite hits" station. They probably sound the same! I've tried to standardize the format names a little. Click here for information regarding radio station formats. In addition to the "Big 4" television networks (ABC, CBS, NBC and Fox), there are number of smaller networks. Some have general audience programming, like UPN, The WB and PaxNet. Others, like America One, The Box and Trinity Broadcast Network cater to a specific group or taste. Then there's public television.

RDS

Radio Data Service is a data stream within the FM carrier. It has the capability to transmit all kinds of information, like station call sign, song names and even radio coupons. Check out the RDS Forum for more information.

AM Stereo

Some (not enough in my opinion) AM stations broadcast in stereo. They use the Motorola C-QUAM system, which was recently adopted as the official AM stereo method by the FCC, after years of letting us languish with a bunch of non compatible standards. AM stereo actually sounds quite good! Many late model car stereos can decode AM stereo. Only one (now discontinued) portable radio was recently for sale, the Sony SRF-42 Walkman. It was kind of cheap, but was AMAX certified, meaning it met certain requirements or decent sound. If you look, you might find one at a local Radio Shack for only US$30. AM stereo is much more popular in some Asian countries like Japan. It is also quite popular in Australia.

TV SAP / Stereo

Television stations can broadcast a stereo signal using a method called MTS (Multi-Channel Stereo) sound. A second channel of audio can be carried as well. SAP (Second Audio Program) is the name of this second channel. It is monaural and relatively lo-fi. Our local public television stations use a SAP channel to carry descriptive video service audio (DVS usually fills any quiet parts of a program's audio with a voice describing the scene or motions of actors on screen) and audio for The Alabama Radio Reading Service for the Blind. Some stations, like WBRC in Birmingham carry weather reports. In other parts of the country, where a second language is widely spoken, the SAP is used for dubbed audio. WBRC recently aired an episode of Cops where the SAP was used for Spanish language dubs. Many cable companies provide SAP channels for networks like HBO, Cinemax and Cartoon Network, who provide extensive Spanish language programming.