Sec. 15.33  Frequency range of radiated measurements.

    (a) For an intentional radiator, the spectrum shall be investigated 
from the lowest radio frequency signal generated in the device, without 
going below 9 kHz, up to at least the frequency shown in this paragraph:
    (1) If the intentional radiator operates below 10 GHz: to the tenth 
harmonic of the highest fundamental frequency or to 40 GHz, whichever is 
lower.

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    (2) If the intentional radiator operates at or above 10 GHz and 
below 30 GHz: to the fifth harmonic of the highest fundamental frequency 
or to 100 GHz, whichever is lower.
    (3) If the intentional radiator operates at or above 30 GHz: to the 
fifth harmonic of the highest fundamental frequency or to 200 GHz, 
whichever is lower.
    (4) If the intentional radiator contains a digital device, 
regardless of whether this digital device controls the functions of the 
intentional radiator or the digital device is used for additional 
control or function purposes other than to enable the operation of the 
intentional radiator, the frequency range shall be investigated up to 
the range specified in paragraphs (a)(1) through (a)(3) of this section 
or the range applicable to the digital device, as shown in paragraph 
(b)(1) of this section, whichever is the higher frequency range of 
investigation.
    (b) For unintentional radiators:
    (1) Except as otherwise indicated in paragraphs (b)(2) or (b)(3) of 
this section, for an unintentional radiator, including a digital device, 
the spectrum shall be investigated from the lowest radio frequency 
signal generated or used in the device, without going below the lowest 
frequency for which a radiated emission limit is specified, up to the 
frequency shown in the following table:

                                                                        
------------------------------------------------------------------------
Highest frequency generated or used in the                              
 device or on which the device operates or       Upper frequency of     
                tunes (MHz)                    measurement range (MHz)  
------------------------------------------------------------------------
Below 1.705...............................  30.                         
1.705-108.................................  1000.                       
108-500...................................  2000.                       
500-1000..................................  5000.                       
Above 1000................................  5th harmonic of the highest 
                                             frequency or 40 GHz,       
                                             whichever is lower.        
------------------------------------------------------------------------

    (2) A unintentional radiator, excluding a digital device, in which 
the highest frequency generated in the device, the highest frequency 
used in the device and the highest frequency on which the device 
operates or tunes are less than 30 MHz and which, in accordance with 
Sec. 15.109, is required to comply with standards on the level of 
radiated emissions within the frequency range 9 kHz to 30 MHz, such as a 
CB receiver or a device designed to conduct its radio frequency 
emissions via connecting wires or cables, e.g., a carrier current system 
not intended to radiate, shall be investigated from the lowest radio 
frequency generated or used in the device, without going below 9 kHz (25 
MHz for CB receivers), up to the frequency shown in the following table. 
If the unintentional radiator contains a digital device, the upper 
frequency to be investigated shall be that shown in the table below or 
in the table in paragraph (b)(1) of this section, as based on both the 
highest frequency generated and the highest frequency used in the 
digital device, whichever range is higher.

                                                                        
------------------------------------------------------------------------
                                                                Upper   
                                                              frequency 
  Highest frequency generated or used in the device or on         of    
          which the device operates or tunes (MHz)           measurement
                                                             range (MHz)
------------------------------------------------------------------------
Below 1.705................................................           30
1.705-10...................................................          400
10-30......................................................          500
------------------------------------------------------------------------

    (3) Except for a CB receiver, a receiver employing superheterodyne 
techniques shall be investigated from 30 MHz up to at least the second 
harmonic of the highest local oscillator frequency generated in the 
device. If such receiver is controlled by a digital device, the 
frequency range shall be investigated up to the higher of the second 
harmonic of the highest local oscillator frequency generated in the 
device or the upper frequency of the measurement range specified for the 
digital device in paragraph (b)(1) of this section.
    (c) The above specified frequency ranges of measurements apply to 
the measurement of radiated emissions and, in the case of receivers, the 
measurement to demonstrate compliance with the antenna conduction limits 
specified in Sec. 15.111. The frequency range of measurements for AC 
power line conducted limits is specified in Secs. 15.107 and 15.207 and 
applies to all equipment subject to those regulations. In some cases, 
depending on the frequency(ies) generated and used by the equipment, 
only signals conducted onto the AC power lines are required to be 
measured.
    (d) Particular attention should be paid to harmonics and 
subharmonics of the fundamental frequency as well as

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to those frequencies removed from the fundamental by multiples of the 
oscillator frequency. Radiation at the frequencies of multiplier states 
should also be checked.
[ 54 FR 17714 , Apr. 25, 1989, as amended at  61 FR 14502 , Apr. 2, 1996