Sec. 73.701  Definitions.

    The following definitions apply to terminology employed in this 
subpart:
    (a) International broadcasting stations. A broadcasting station 
employing frequencies allocated to the broadcasting service between 
5,950 and 26,100 kHz, the transmissions of which are intended to be 
received directly by the general public in foreign countries. (A station 
may be authorized more than one transmitter.) There are both government 
and non-government international broadcasting stations; only the latter 
are licensed by the Commission and are subject to the rules of this 
subpart.
    (b) Transmitter-hour. One frequency used on one transmitter for one 
hour.
    (c) Frequency-hour. One frequency used for one hour regardless of 
the number of transmitters over which it is simultaneously broadcast by 
a station during that hour.
    (d) Multiple operation. Broadcasting by a station on one frequency 
over two or more transmitters simultaneously. If a station uses the same 
frequency simultaneously on each of two (three, etc.) transmitters for 
an hour, it uses one frequency-hour and two (three, etc.) transmitter-
hours.
    (e) Day. Any twenty-four hour period beginning 0100 g.m.t. and 
ending 0100 g.m.t.
    (f) Sunspot number. The 12-month running average of the number of 
sunspots for any month as indicated in the

[[Page 245]]

U.S. Department of Commerce Telecommunications Research and Engineering 
Report No. 13--available from the Superintendent of Documents, 
Washington, DC 20402. The sunspot number varies in an approximate 11-
year cycle.
    (g) March season. That portion of any year commencing 0100 g.m.t. on 
the first Sunday in March and ending at 0100 g.m.t. on the first Sunday 
in May.
    (h) May season. That portion of any year commencing at 0100 G.M.T. 
on the first Sunday in May and ending at 0100 g.m.t. on the first Sunday 
in September.
    (i) September season. That portion of any year commencing at 0100 
g.m.t. on the first Sunday in September and ending at 0100 g.m.t. on the 
first Sunday in November.
    (j) November season. That portion of any year commencing at 0100 
g.m.t. on the first Sunday in November and ending at 0100 g.m.t. on the 
first Sunday in March.
    (k) Seasonal schedule. An assignment, for a season, of a frequency 
or frequencies, and other technical parameters, to be used by a station 
for transmission to particular zones or areas of reception during 
specified hours.
    (l) Reference month. That month of a season which is used for 
determining predicted propagation characteristics for the season. The 
reference month is January, April, July, or October, as related to the 
season in which it occurs.
    (m) Maximum usable frequency (MUF). The highest frequency which is 
returned by ionospheric radio propagation to the surface of the earth 
for a particular path and time of day for 50 percent of the days of the 
reference month.
    (n) Optimum working frequency (FOT). The highest frequency which is 
returned by ionospheric radio propagation to the surface of the earth 
for a particular path and time of day for 90 percent of the days of the 
reference month.

    Note: The international abbreviation for optimum working frequency, 
FOT, is formed with the initial letters of the French words for 
``optimum working frequency'' which are ``frequence optimum de 
travail.''

    (o) Zone of reception. Any geographic zone indicated in Sec. 73.703 
in which the reception of particular programs is specifically intended 
and in which broadcast coverage is contemplated.
    (p) Area of reception. Any geographic area smaller than a zone of 
reception in which the reception of particular programs is specifically 
intended and in which broadcast coverage is contemplated, such areas 
being indicated by countries or parts of countries.
    (q) Delivered median field strength, or field strength. The field 
strength incident upon the zone or area of reception expressed in 
microvolts per meter, or decibels above one microvolt per meter, which 
is exceeded by the hourly median value for 50 percent of the days of the 
reference month.
    (r) Carrier power. The average power supplied to the antenna 
transmission line by a transmitter during one radio frequency cycle 
under conditions of no modulation.

[ 38 FR 18892 , July 16, 1973]