Sec. 18.305  Field strength limits.

    (a) ISM equipment operating on a frequency specified in Sec. 18.301 
is permitted

[[Page 689]]

unlimited radiated energy in the band specified for that frequency.
    (b) The field strength levels of emissions which lie outside the 
bands specified in Sec. 18.301, unless otherwise indicated, shall not 
exceed the following:

-------------------------------------------------------------------------------
---------------------------------
                                                           RF Power generated b
y  Field strength limit  Distance
             Equipment               Operating frequency     equipment (watts) 
          (uV/m)         (meters)
-------------------------------------------------------------------------------
---------------------------------
Any type unless otherwise           Any ISM frequency....  Below 500...........
.  25..................       300
 specified (miscellaneous).                                500 or more.........
.  25 x SQRT(power/500)    \1\300
                                    Any non-ISM frequency  Below 500...........
.  15..................       300
                                                           500 or more.........
.  15 x SQRT(power/500)    \1\300
Industrial heaters and RF           On or below 5,725 MHz  Any.................
.  10..................     1,600
 stabilized arc welders.            Above 5,725 MHz......  Any.................
.  (\2\)...............     (\2\)
Medical diathermy.................  Any ISM frequency....  Any.................
.  25..................       300
                                    Any non-ISM frequency  Any.................
.  15..................       300
Ultrasonic........................  Below 490 kHz........  Below 500...........
.  2,400/F(kHz)........       300
                                                           500 or more.........
.  2,400/F(kHz) x          \3\300
                                                                               
    SQRT(power/500).             
                                    490 to 1,600 kHz.....  Any.................
.  24,000/F(kHz).......        30
                                    Above 1,600 kHz......  Any.................
.  15..................        30
Induction cooking ranges..........  Below 90 kHz.........  Any.................
.  1,500...............     \4\30
                                    On or above 90 kHz...  Any.................
.  300.................     \4\30
-------------------------------------------------------------------------------
---------------------------------
\1\ Field strength may not exceed 10 V/m at 1600 meters. Consumer equi
pment operating below 1000 MHz is
  not permitted the increase in field strength otherwise permitted here for pow
er over 500 watts.               
\2\ Reduced to the greatest extent possible.                                   
                                 
\3\ Field strength may not exceed 10 V/m at 1600 meters. Consumer equi
pment is not permitted the       
  increase in field strength otherwise permitted here for over 500 watts.      
                                 
\4\ Induction cooking ranges manufactured prior to February 1, 1980, shall be s
ubject to the field strength     
  limits for miscellaneous ISM equipment.                                      
                                 

    (c) The field strength limits for RF lighting devices shall be the 
following:

------------------------------------------------------------------------
                                            Field strength limit at 30  
             Frequency (MHz)                   meters (V/m)    
------------------------------------------------------------------------
Non-consumer equipment:                                                 
    30-88...............................                30              
    88-216..............................                50              
    216-1000............................                70              
Consumer equipment:                                                     
    30-88...............................                10              
    88-216..............................                15              
    216-1000............................                20              
------------------------------------------------------------------------

                                  Notes

    1. The tighter limit shall apply at the boundary between two 
frequency ranges.
    2. Testing for compliance with these limits may be made at closer 
distances, provided a sufficient number of measurements are taken to 
plot the radiation pattern, to determine the major lobes of radiation, 
and to determine the expected field strength level at 30, 300, or 1600 
meters. Alternatively, if measurements are made at only one closer fixed 
distance, then the permissible field strength limits shall be adjusted 
using 1/d as an attenuation factor.
[ 50 FR 36070 , Sept. 5, 1985, as amended at  51 FR 17970 , May 16, 1986;  52 FR 43197 , Nov. 10, 1987]