§  74.644   Minimum path lengths for fixed links.

   (a) The distance between end points of a fixed link must equal or
   exceed the value set forth in the table below or the EIRP must be
   reduced in accordance with the equation set forth below.
   Frequency band
   (MHz) Minimum path length
   (km)
         Below 1,990        n/a
         1,990–7,125         17
         12,200–13,250        5
         Above 17,700       n/a

   (b) For paths shorter than those specified in the Table, the EIRP shall
   not exceed the value derived from the following equation.

   EIRP = MAXEIRP−40 log(A/B) dBW

   Where:

   EIRP = The new maximum EIRP (equivalent isotropically radiated power)
   in dBW.

   MAXEIRP = Maximum EIRP as set forth in the Table in § 74.636 of this
   part.

   A = Minimum path length from the Table above for the frequency band in
   kilometers.

   B = The actual path length in kilometers.

   Note 1 to paragraph(b): For transmitters using Automatic Transmitter
   Power Control, EIRP corresponds to the maximum transmitter power
   available, not the coordinated transmit power or the nominal transmit
   power.

   Note 2 to paragraph(b): Stations licensed based on an application filed
   before April 16, 2003, in the 2450–2483.5 MHz band, for EIRP values
   exceeding those specified above, may continue to operate indefinitely
   in accordance with the terms of their current authorizations, subject
   to periodic renewal.

   (c) Upon an appropriate technical showing, applicants and licensees
   unable to meet the minimum path length requirement may be granted an
   exception to these requirements.

   Note: Links authorized prior to April 1, 1987, are excluded from this
   requirement, except that, effective April 1, 1992, the Commission will
   require compliance with the criteria where an existing link would
   otherwise preclude establishment of a new link.

   [ 52 FR 7143 , Mar. 9, 1987, as amended at  68 FR 12771 , Mar. 17, 2003]