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 &177;10 degrees of the

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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 &177;** 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]