Sec.  15.247   Operation within the bands 902–928 MHz, 2400–2483.5 MHz, and
5725–5850 MHz.

   (a) Operation under the provisions of this Section is limited to frequency
   hopping and digitally modulated intentional radiators that comply with the
   following provisions:

   (1) Frequency hopping systems shall have hopping channel carrier frequencies
   separated by a minimum of 25 kHz or the 20 dB bandwidth of the hopping
   channel, whichever is greater. Alternatively, frequency hopping systems
   operating in the 2400–2483.5 MHz band may have hopping channel carrier
   frequencies that are separated by 25 kHz or two-thirds of the 20 dB
   bandwidth of the hopping channel, whichever is greater, provided the systems
   operate with an output power no greater than 125 mW. The system shall hop to
   channel frequencies that are selected at the system hopping rate from a
   pseudo randomly ordered list of hopping frequencies. Each frequency must be
   used equally on the average by each transmitter. The system receivers shall
   have input bandwidths that match the hopping channel bandwidths of their
   corresponding transmitters and shall shift frequencies in synchronization
   with the transmitted signals.

   (i) For frequency hopping systems operating in the 902–928 MHz band: if the
   20 dB bandwidth of the hopping channel is less than 250 kHz, the system
   shall use at least 50 hopping frequencies and the average time of occupancy
   on any frequency shall not be greater than 0.4 seconds within a 20 second
   period; if the 20 dB bandwidth of the hopping channel is 250 kHz or greater,
   the system shall use at least 25 hopping frequencies and the average time of
   occupancy on any frequency shall not be greater than 0.4 seconds within a 10
   second period. The maximum allowed 20 dB bandwidth of the hopping channel is
   500 kHz.

   (ii) Frequency hopping systems operating in the 5725–5850 MHz band shall use
   at least 75 hopping frequencies. The maximum 20 dB bandwidth of the hopping
   channel is 1 MHz. The average time of occupancy on any frequency shall not
   be greater than 0.4 seconds within a 30 second period.

   (iii) Frequency hopping systems in the 2400–2483.5 MHz band shall use at
   least 15 channels. The average time of occupancy on any channel shall not be
   greater than 0.4 seconds within a period of 0.4 seconds multiplied by the
   number of hopping channels employed. Frequency hopping systems may avoid or
   suppress transmissions on a particular hopping frequency provided that a
   minimum of 15 channels are used.

   (2) Systems using digital modulation techniques may operate in the 902–928
   MHz, 2400–2483.5 MHz, and 5725–5850 MHz bands. The minimum 6 dB bandwidth
   shall be at least 500 kHz.

   (b) The maximum peak conducted output power of the intentional radiator
   shall not exceed the following:

   (1) For frequency hopping systems operating in the 2400–2483.5 MHz band
   employing at least 75 non-overlapping hopping channels, and all frequency
   hopping systems in the 5725–5850 MHz band: 1 watt. For all other frequency
   hopping systems in the 2400–2483.5 MHz band: 0.125 watts.

   (2) For frequency hopping systems operating in the 902–928 MHz band: 1 watt
   for systems employing at least 50 hopping channels; and, 0.25 watts for
   systems employing less than 50 hopping channels, but at least 25 hopping
   channels, as permitted under paragraph (a)(1)(i) of this section.

   (3) For systems using digital modulation in the 902–928 MHz, 2400–2483.5
   MHz, and 5725–5850 MHz bands: 1 Watt. As an alternative to a peak power
   measurement, compliance with the one Watt limit can be based on a
   measurement of the maximum conducted output power. Maximum Conducted Output
   Power is defined as the total transmit power delivered to all antennas and
   antenna elements averaged across all symbols in the signaling alphabet when
   the transmitter is operating at its maximum power control level. Power must
   be summed across all antennas and antenna elements. The average must not
   include any time intervals during which the transmitter is off or is
   transmitting at a reduced power level. If multiple modes of operation are
   possible (e.g., alternative modulation methods), the maximum conducted
   output power is the highest total transmit power occurring in any mode.

   (4) The conducted output power limit specified in paragraph (b) of this
   section is based on the use of antennas with directional gains that do not
   exceed 6 dBi. Except as shown in paragraph (c) of this section, if
   transmitting antennas of directional gain greater than 6 dBi are used, the
   conducted output power from the intentional radiator shall be reduced below
   the stated values in paragraphs (b)(1), (b)(2), and (b)(3) of this section,
   as appropriate, by the amount in dB that the directional gain of the antenna
   exceeds 6 dBi.

   (i) Systems operating in the 2400–2483.5 MHz band that are used exclusively
   for fixed, point-to-point operations may employ transmitting antennas with
   directional gain greater than 6 dBi provided the maximum peak output power
   of the intentional radiator is reduced by 1 dB for every 3 dB that the
   directional gain of the antenna exceeds 6 dBi.

   (ii) Systems operating in the 5725–5850 MHz band that are used exclusively
   for fixed, point-to-point operations may employ transmitting antennas with
   directional gain greater than 6 dBi without any corresponding reduction in
   transmitter peak output power.

   (iii) Fixed, point-to-point operation, as used in paragraphs (b)(3)(i) and
   (b)(3)(ii) of this section, excludes the use of point-to-multipoint systems,
   omnidirectional applications, and multiple co-located intentional radiators
   transmitting the same information. The operator of the spread spectrum
   intentional radiator or, if the equipment is professionally installed, the
   installer is responsible for ensuring that the system is used exclusively
   for fixed, point-to-point operations. The instruction manual furnished with
   the intentional radiator shall contain language in the installation
   instructions informing the operator and the installer of this
   responsibility.

   (5) Systems operating under the provisions of this section shall be operated
   in a manner that ensures that the public is not exposed to radio frequency
   energy levels in excess of the Commission's guidelines. See  Sec. 1.1307(b)(1) of
   this chapter.

   (c) Operation with directional antenna gains greater than 6 dBi.

   (1) Fixed point-to-point operation:

   (i) Systems operating in the 2400–2483.5 MHz band that are used exclusively
   for fixed, point-to-point operations may employ transmitting antennas with
   directional gain greater than 6 dBi provided the maximum conducted output
   power of the intentional radiator is reduced by 1 dB for every 3 dB that the
   directional gain of the antenna exceeds 6 dBi.

   (ii) Systems operating in the 5725–5850 MHz band that are used exclusively
   for fixed, point-to-point operations may employ transmitting antennas with
   directional gain greater than 6 dBi without any corresponding reduction in
   transmitter conducted output power.

   (iii) Fixed, point-to-point operation, as used in paragraphs (c)(1)(i) and
   (c)(1)(ii) of this section, excludes the use of point-to-multipoint systems,
   omnidirectional applications, and multiple co-located intentional radiators
   transmitting the same information. The operator of the spread spectrum or
   digitally modulated intentional radiator or, if the equipment is
   professionally installed, the installer is responsible for ensuring that the
   system is used exclusively for fixed, point-to-point operations. The
   instruction manual furnished with the intentional radiator shall contain
   language in the installation instructions informing the operator and the
   installer of this responsibility.

   (2) In addition to the provisions in paragraphs (b)(1), (b)(3), (b)(4) and
   (c)(1)(i) of this section, transmitters operating in the 2400–2483.5 MHz
   band that emit multiple directional beams, simultaneously or sequentially,
   for the purpose of directing signals to individual receivers or to groups of
   receivers provided the emissions comply with the following:

   (i) Different information must be transmitted to each receiver.

   (ii) If the transmitter employs an antenna system that emits multiple
   directional beams but does not do emit multiple directional beams
   simultaneously, the total output power conducted to the array or arrays that
   comprise the device, i.e., the sum of the power supplied to all antennas,
   antenna elements, staves, etc. and summed across all carriers or frequency
   channels, shall not exceed the limit specified in paragraph (b)(1) or (b)(3)
   of this section, as applicable. However, the total conducted output power
   shall be reduced by 1 dB below the specified limits for each 3 dB that the
   directional gain of the antenna/antenna array exceeds 6 dBi. The directional
   antenna gain shall be computed as follows:

   (A) The directional gain shall be calculated as the sum of 10 log (number of
   array elements or staves) plus the directional gain of the element or stave
   having the highest gain.

   (B) A lower value for the directional gain than that calculated in paragraph
   (c)(2)(ii)(A) of this section will be accepted if sufficient evidence is
   presented, e.g., due to shading of the array or coherence loss in the
   beamforming.

   (iii) If a transmitter employs an antenna that operates simultaneously on
   multiple directional beams using the same or different frequency channels,
   the power supplied to each emission beam is subject to the power limit
   specified in paragraph (c)(2)(ii) of this section. If transmitted beams
   overlap, the power shall be reduced to ensure that their aggregate power
   does not exceed the limit specified in paragraph (c)(2)(ii) of this section.
   In addition, the aggregate power transmitted simultaneously on all beams
   shall not exceed the limit specified in paragraph (c)(2)(ii) of this section
   by more than 8 dB.

   (iv) Transmitters that emit a single directional beam shall operate under
   the provisions of paragraph (c)(1) of this section.

   (d) In any 100 kHz bandwidth outside the frequency band in which the spread
   spectrum or digitally modulated intentional radiator is operating, the radio
   frequency power that is produced by the intentional radiator shall be at
   least 20 dB below that in the 100 kHz bandwidth within the band that
   contains the highest level of the desired power, based on either an RF
   conducted or a radiated measurement, provided the transmitter demonstrates
   compliance with the peak conducted power limits. If the transmitter complies
   with the conducted power limits based on the use of RMS averaging over a
   time interval, as permitted under paragraph (b)(3) of this section, the
   attenuation required under this paragraph shall be 30 dB instead of 20 dB.
   Attenuation below the general limits specified in  Sec. 15.209(a) is not
   required. In addition, radiated emissions which fall in the restricted
   bands, as defined in  Sec. 15.205(a), must also comply with the radiated emission
   limits specified in  Sec. 15.209(a) (see  Sec. 15.205(c)).

   (e) For digitally modulated systems, the power spectral density conducted
   from the intentional radiator to the antenna shall not be greater than 8 dBm
   in any 3 kHz band during any time interval of continuous transmission. This
   power spectral density shall be determined in accordance with the provisions
   of paragraph (b) of this section. The same method of determining the
   conducted output power shall be used to determine the power spectral
   density.

   (i) Systems operating under the provisions of this section shall be operated
   in a manner that ensures that the public is not exposed to radio frequency
   energy levels in excess of the Commission's guidelines. See  Sec. 1.1307(b)(1) of
   this chapter.

   (f) For the purposes of this section, hybrid systems are those that employ a
   combination of both frequency hopping and digital modulation techniques. The
   frequency hopping operation of the hybrid system, with the direct sequence
   or digital modulation operation turned off, shall have an average time of
   occupancy on any frequency not to exceed 0.4 seconds within a time period in
   seconds equal to the number of hopping frequencies employed multiplied by
   0.4. The digital modulation operation of the hybrid system, with the
   frequency hopping operation turned off, shall comply with the power density
   requirements of paragraph (d) of this section.

   (g) Frequency hopping spread spectrum systems are not required to employ all
   available hopping channels during each transmission. However, the system,
   consisting of both the transmitter and the receiver, must be designed to
   comply with all of the regulations in this section should the transmitter be
   presented with a continuous data (or information) stream. In addition, a
   system employing short transmission bursts must comply with the definition
   of a frequency hopping system and must distribute its transmissions over the
   minimum number of hopping channels specified in this section.

   (h) The incorporation of intelligence within a frequency hopping spread
   spectrum system that permits the system to recognize other users within the
   spectrum band so that it individually and independently chooses and adapts
   its hopsets to avoid hopping on occupied channels is permitted. The
   coordination of frequency hopping systems in any other manner for the
   express purpose of avoiding the simultaneous occupancy of individual hopping
   frequencies by multiple transmitters is not permitted.

   Note: Spread spectrum systems are sharing these bands on a noninterference
   basis with systems supporting critical Government requirements that have
   been allocated the usage of these bands, secondary only to ISM equipment
   operated under the provisions of part 18 of this chapter. Many of these
   Government systems are airborne radiolocation systems that emit a high EIRP
   which can cause interference to other users. Also, investigations of the
   effect of spread spectrum interference to U. S. Government operations in the
   902–928 MHz band may require a future decrease in the power limits allowed
   for spread spectrum operation.

   [ 54 FR 17714 , Apr. 25, 1989, as amended at  55 FR 28762 , July 13, 1990;  62 FR 26242 , May 13, 1997;  65 FR 57561 , Sept. 25, 2000;  67 FR 42734 , June 25,
   2002;  69 FR 54035 , Sept. 7, 2004]