Talk:Clear channel

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This article gets a bunch of things wrong. For starters, a "clear channel" is by definition a station which does not share its channel with any other. The old I-Bs were never "clear channel" stations, nor were the I-Ns, and this status was completely eliminated by the "Rio accord". The long list of stations ought to be labeled something like "List of stations in North America which are called out as being of class A under the ITU Region II Mediumwave Coordination Agreement of 1981" or some such.

There are important differences between class A stations and class B stations, even though the clear channels as such no longer exist. Specifically:

• Class A stations must operate with at least 10 kW, and are restricted to specific locations and frequencies set out under Rio and previous international agreements. CBE and CBN are the last 10-kW class-A's.
• Class A stations, unlike all others, have a protected nighttime skywave ("secondary") service area.
• Class A stations, unlike all others, are entitled to protection from daytime skywave interference to their groundwave ("primary") service area (mostly a factor on the high end of the band, 1500 to 1560 kHz).
• Class A stations must meet a higher minimum antenna-system efficiency than class B stations.
• Once a station has lost class A status, it can never regain it. By contrast, a class B station may relinquish nighttime authority (thereby becoming a class D) and then later be returned to class B upon grant of an application to resume night operation. This has happened, in the case of WOWO, which was demoted from A to B in order that WLIB might be promoted from D to B. (With WOWO protected as an A, WLIB could not operate at night; as a B, WOWO no longer has a protected secondary service area, so WLIB need only protect WOWO's groundwave.)
• Class A stations have generally not been subject to the "ratcheting" rules which require modifications to AM station facilities to reduce interference by at least 10%.

Class A includes all of the stations formerly designated as class I-A, I-B, or I-N. Class B includes the former classes II (secondary assignments on I-B channels) and III (regional channels, limited to 5 kW nominal power), except II-D and III-D which became class D. Class C is the former class IV (graveyard channels).

The breakdown of the clear channels began in the 1960s, when the FCC began assigning class II-B stations in the West on Eastern class I-A channels; in one case (KOB Albuquerque versus WABC on 770) the matter went all the way to the Supreme Court (and was decided in the FCC's and KOB's favor). In a last-gasp attempt to preserve their relevance, several of the I-A stations asked the FCC to increase the power limit from 50 kW to 750 kW. This was eventually turned down when even many of the I-A stations came out against it.

Protection of foreign class-A stations is still much stronger than protection of domestic class-A stations, in all three countries. This is an artifact of the requirement in NARBA that all stations on another country's I-A channel protect the entire border of the assigned country.

Oh, and nearly all of the callsigns in that big long list are wrong as well. Tain't no such thing as "-AM".

18.26.0.18 05:45, 25 Jan 2005 (UTC)

[edit] Data source

The data in the updated version of the table comes from the FCC's Consolidated Database System (CDBS). The following SQL query was used to extract the relevant information from the public CDBS dumps:

 select distinct fac_callsign as "Call",
                 fac_frequency as "Freq.",
                 comm_city as "City",
                 station_class as "Cl.",
                 region_2_class as "R2",
                 old_station_class as "Old"
     from facility join am_eng_data using (facility_id)
     where station_class = 'A' and 
           fac_country in ('US', 'CA', 'MX')
     order by fac_frequency, fac_callsign

I then filtered the data for known errors and silent stations, and added ZNS1 back in (since The Bahamas counts as "North American"). 121a0012 19:04, May 30, 2005 (UTC)