Sec.  18.305   Field strength limits.

   (a) ISM equipment operating on a frequency specified in  Sec. 18.301 is permitted
   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.........
.  25xSQRT(power/500)..    \1\300
                                    Any non-ISM frequency  Below 500...........
.  15..................       300
                                                           500 or more.........
.  15xSQRT(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 mV/m at 1600 meters. Consumer equipment op
erating below 1000 MHz is not
  permitted the increase in field strength otherwise permitted here for power o
ver 500 watts.
\2\ Reduced to the greatest extent possible.
\3\ Field strength may not exceed 10 mV/m at 1600 meters. Consumer equipment 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 meters
           Frequency (MHz)                          (mV/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]