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FCC Part 15 Radio Frequency Devices
Section 15.247

The Federal Communications Commission (FCC) is the authority in the United States of America that creates and enforces the use of airwaves throughout the entire radio frequency spectrum. This group of documents contains the entirety of the FCC Part 15 regulations that concern unlicensed radio frequency devices. As with all government documents, this material is in the public domain and may be freely copied so long as the content is not changed. This copy is provided as a convenience for RF Cafe visitors. 

Click here for the Table of Contents.

 
[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.247]
[Page 818-822]
 
                       TITLE 47--TELECOMMUNICATION
 
              CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
 
PART 15_RADIO FREQUENCY DEVICES--Table of Contents
 
                     Subpart C_Intentional Radiators
 
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
[[Page 819]]
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.
[[Page 820]]
    (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.
    (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
[[Page 821]]
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.
    (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.
    (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
[[Page 822]]
energy levels in excess of the Commission's guidelines. See Sec. 
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]



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