Sec.  15.251   Operation within the bands 2.9-3.26 GHz, 3.267-3.332 GHz,
3.339-3.3458 GHz, and 3.358-3.6 GHz.

   

   (a) Operation under the provisions of this section is limited to
   automatic vehicle identification systems (AVIS) which use swept
   frequency techniques for the purpose of automatically identifying
   transportation vehicles.

   (b) The field strength anywhere within the frequency range swept by
   the signal shall not exceed 3000 microvolts/meter/MHz at 3 meters in
   any direction. Further, an AVIS, when in its operating position, shall
   not produce a field strength greater than 400 microvolts/meter/MHz at
   3 meters in any direction within ±10 degrees of the horizontal plane.
   In addition to the provisions of Sec. 15.205, the field strength of
   radiated emissions outside the frequency range swept by the signal
   shall be limited to a maximum of 100 microvolts/meter/MHz at 3 meters,
   measured from 30 MHz to 20 GHz for the complete system. The emission
   limits in this paragraph are based on measurement instrumentation
   employing an average detector. The provisions in Sec. 15.35 for limiting
   peak emissions apply.

   (c) The minimum sweep repetition rate of the signal shall not be lower
   than 4000 sweeps per second, and the maximum sweep repetition rate of
   the signal shall not exceed 50,000 sweeps per second.

   (d) An AVIS shall employ a horn antenna or other comparable
   directional antenna for signal emission.

   (e) Provision shall be made so that signal emission from the AVIS
   shall occur only when the vehicle to be identified is within the
   radiated field of the system.

   (f) In addition to the labelling requirements in Sec. 15.19(a), the label
   attached to the AVIS transmitter shall contain a third statement
   regarding operational conditions, as follows:

    *  *  * and, (3) during use this device (the antenna) may not be
   pointed within ±** degrees of the horizontal plane.

   The double asterisks in condition three (**) shall be replaced by the
   responsible party with the angular pointing restriction necessary to
   meet the horizontal emission limit specified in paragraph (b).

   (g) In addition to the information required in subpart J of part 2,
   the application for certification shall contain:

   (1) Measurements of field strength per MHz along with the intermediate
   frequency of the spectrum analyzer or equivalent measuring receiver;

   (2) The angular separation between the direction at which maximum
   field strength occurs and the direction at which the field strength is
   reduced to 400 microvolts/meter/MHz at 3 meters;

   (3) A photograph of the spectrum analyzer display showing the entire
   swept frequency signal and a calibrated scale for the vertical and
   horizontal axes; the spectrum analyzer settings that were used shall
   be labelled on the photograph; and,

   (4) The results of the frequency search for spurious and sideband
   emissions from 30 MHz to 20 GHz, exclusive of the swept frequency
   band, with the measuring instrument as close as possible to the unit
   under test.

   [ 54 FR 17714 , Apr. 25, 1989;  54 FR 32340 , Aug. 7, 1989]