Are there still clear channel stations in the U.S? I thought they dropped
that years ago.

scott


"Peter H." wrote in message
...


I always have wanted to know how much power are stations allowed to
operate.


This is specified by international treaties. For North America, this would
be
the North America Regional Broadcast Agreement (signed 1939, effective
1941),
and the subsequent U.S.-Mexico Broadcast Agreement and U.S.-Canada
Broadcast
Agreement.

For Class I-A stations, only, the wording was stated to be "at least
50,000
watts" because Mexico was already using in excess of 50,000 watts.

For all other Class I-B and Class II-B stations the wording was stated to
be
"50,000 watts".

However, Mexico subsequently authorized 100,000 watts, during daytime
only, for
stations not otherwise entitled by treaty to use more than 50,000 watts.

In fact, for some stations which were limited by treaty to 10,000 watts,
Mexico
also allows 100,000 watts, during daytime only.

The much later "Rio" treaty further modified the rules, and allowed for
the
first time Mexican and Canadian operations on U.S. clear channels, as well
as
unrestricted operation of U.S. stations on Mexican clears.

(The earlier NARBA treaty had already authorized U.S. operations on
Canadian
clears, provided the stations were more than 650 miles from the
U.S.-Canadian
border).


I remember while living in Mexico, listening to XEWA 540AM, they used to
operate at 150,000 watts day and night, but now they are less than that,
probably 5000 watts or something.


XEWA was not the original Class I-A occupant of 540.

By 1941's NARBA, 540 was given to Canada as a Class I-A.

By the mid-1950s U.S.-Mexico agreement, 540 was added to Mexico's Class
I-A
list, and that frequency was assigned to San Luis Potosi, at 150,000
watts.

IIRC, XEWA is still operating with 150,000 watts.

Certainly, it is "notified" and authorized to do so.



XEW 900 is well known, they use 250,000 watts and say they cover most of
North
America.


NARBA also gave the U.S. night time priority on 800 and 900 in Alaska,
although
one of those stations has been changed to a U.S. clear channel on account
of
excessive interference from Canada.

Insofar as the U.S.-Mexican treaty, the U.S. includes all states and
territories, so Hawaii, Alaska and P.R. are included, even though these
states
and territories really can't interfere with Mexico's "notified"
operations.

However, Canada, not being contiguous with Mexico, used all Mexican clears
for
whatever purpose it wanted. It's just that Canada could not "notify" any
Class
I stations on those frequencies.

Additionally, the U.S.-Mexican treaty prohibited the U.S. from operating
any
station on Mexican clears at night, and also prevented any day operations
greater than 1 kW. Unless specifically excepted by treaty, which covered
the
50,000 watt DA-1 operations in Cleveland (1220) and New York (1050), and
the
5,000 watt operation in Alaska (800 and 900).



American stations use at most 50,000 watts and they are forced to lower
their
power at night, while at the same time, one station, I think is in Mexico
City,
goes from 5,000 to 150,000 at nights.


U.S., Canada and The Bahamas have a 50,000 watt limit.

Unless a specific station is "notified" for lower power at night, the same
power may be used night as well as day.

Class I-A and I-B (now Class A) stations are permitted a flat 50,000 watts
(more for Mexico, under the conditions described above).

That is, unless the Class A is "grandfathered" at a lower power, say,
10,000
watts.

There is only one U.S. Class A station which is so grandfathered.

There is one Canadian stations which is so grandfathered (1550).

There are three Mexican stations which are so grandfathered (1000, 1190
and
1550).



Any explanation would be appreciated and one question, Is there any pros
and
cons of running that much power?


Lots of power was needed to cover "underserved" areas in decades past.

Lots of power is now needed in order to overcome all the man-made
interference
from the gazillions of switching power supplies used in computers and
entertainment appliances.

With "Rio" stations which were formerly limited to 5,000 watts were
allowed to
increase to 50,000 watts.

Practically speaking, this only applies to "historical" Class III-A
stations
(KJR, KMJ, KKOL, KXTA, etcetera, etcetera, etcetera) as these Class III-A
stations received better protection then Class III stations of inferior
priority (Class III-B, e.g.).



How about other countries, whats the most power a station can have?


In Europe, there is/was a 1,400,000 watt station.

But, because of unauthorized use by other countries (Cypress and Israel,
IIRC)
the 1,400,000 watts is largely wasted at night.