§ 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.

   (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 § 15.209(a) is
   not required. In addition, radiated emissions which fall in the
   restricted bands, as defined in § 15.205(a), must also comply with the
   radiated emission limits specified in § 15.209(a) (see § 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.

   (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 power spectral density
   conducted from the intentional radiator to the antenna due to the
   digital modulation operation of the hybrid system, with the frequency
   hopping operation turned off, shall not be greater than 8 dBm in any 3
   kHz band during any time interval of continuous transmission.

   Note to paragraph (f): The transition provisions found in § 15.37(h)
   will apply to hybrid devices beginning June 2, 2015.

   (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.

   (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 § 1.1307(b)(1) of this chapter.

   [ 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;  72 FR 5632 , Feb. 7, 2007;  79 FR 24578 , May 1, 2014]

   return arrow Back to Top