Sec. 21.42  Certain modifications not requiring prior authorization.

    (a) Equipment in an authorized radio station may be replaced without 
prior authorization or notification if:
    (1) The replacement equipment is identical (i.e., same manufacturer 
and model number) with the replacement equipment; or
    (2) The replacement transmitter, transmitting antenna, transmission 
line loss and/or devices between the transmitter and antenna, or 
combinations of the above, do not change the EIRP of a station in any 
direction.
    (b) Licensees of fixed stations in the Multipoint Distribution 
Service may make the facility changes listed in paragraph (c) of this 
section without obtaining prior Commission authorization, if:
    (1) The Multipoint Distribution Service licensee serves a copy of 
the notification described in paragraph (b)(3) of this section on those 
who were served under Sec. 21.902, and
    (2) The cumulative effect of all facility changes made within any 60 
day period does not exceed the appropriate values prescribed by 
paragraph (c) of this section, and
    (3) The Commission is notified of changes made to facilities by the 
submission of a completed FCC Form 494, or for the Multipoint 
Distribution Service, and MDS long-form application, as applicable, 
within thirty days after the changes are made.
    (4) In the Multipoint Distribution Service, the modified facility 
would not produce a power flux density at the protected service area 
boundary that exceeds -73 dBW/m\2\, pursuant to Secs. 21.902 and 21.939.
    (c) Modifications that may be made without prior authorization under 
paragraph (b) of this section are:
    (1) Change or modification of a transmitter, when:
    (i) The replacement or modified transmitter is type-accepted (or 
type-notified) for use under this part and is installed without 
modification from the type-accepted (or type notified) configuration;
    (ii) The type of modulation is not changed;
    (iii) The frequency stability is equal to or better than the 
previously authorized frequency stability; and
    (iv) The necessary bandwidth and the output power do not exceed the 
previously authorized values.
    (2) Addition or deletion of a transmitter for protection without 
changing the authorized power output (e.g. hot standby transmitters);
    (3) Change to an antenna when the new antenna conforms with 
Sec. 21.906 and the EIRP resulting from the new antenna does not exceed 
that resulting from the previously authorized antenna by more than one 
dB in any direction.
    (4) Any technical changes that would decrease the effective radiated 
power.
    (5) Change to the height of an antenna, when:
    (i) The new height (measured at the center-of-radiation) is within 
&177;1.5 meters (5 feet) of the previously authorized height; and
    (ii) The overall height of the antenna structure is not increased as 
a result of the antenna extending above the height of the previously 
authorized structure, except when the new height of the antenna 
structure is 6.1 meters (20 feet) or less (above ground or man-made 
structure, as appropriate) after the change is made.
    (6) Decreases in the overall height of an antenna structure, 
provided that, when notice to the FAA of proposed construction was 
required by part 17 of this chapter for the antenna structure at the 
previously authorized height, the applicant must comply with the 
provisions of Sec. 21.15 (d) and (e).
    (7) Changes to the transmission line and other devices between the 
transmitter and the antenna when the effective radiated power of the 
station is not increased by more than one dB.
    (d) Licensees may correct erroneous information on a license which 
does not involve a major change (i.e., a change that would be classified 
as a

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major amendment as defined by Sec. 21.23) without obtaining prior 
Commission approval by filing a completed FCC Form 494, or for the 
Multipoint Distribution Service licensees, by filing the MDS long-form 
application.
[ 52 FR 37781 , Oct. 9, 1987, as amended at  58 FR 44894 , Aug. 25, 1993;  60 FR 36552 , July 17, 1995;  60 FR 57366 , Nov. 15, 1995;  61 FR 4364 , Feb. 6, 
1996;  61 FR 26674 , May 28, 1996]