§  2.1503   Test environment.

   (a) Measurement sites. Radiated emission tests for peak effective
   radiated power (PERP), spurious emissions and power in the test mode
   are to be performed on an open field test site as shown in Figure 1.
   The site is to be located on level ground with an obstruction-free, 60
   m by 52 m, elliptical area. The site is to be equipped with an antenna
   mast capable of adjustment from 1 to 4 m. The center of a metal ground
   plane at least one wavelength in diameter at 121.5 MHz (2.47 m) is to
   be located 30 m from the receiving antenna. The ground plane is to have
   provisions for mounting removable quarter-wave verticle elements to
   produce a monopole antenna at both 121.5 and 243 MHz with the VSWR of
   less than 1.5.

   Note: It is desirable that the level of radiated ambient EME at the
   test site be at least 6 dB below the FCC limits applicable to the
   EPIRB. It is, of course, not always possible to meet this condition. If
   the ambient field strength at some frequencies within the specified
   measurement ranges is too high, it is recommended that one or more of
   the following corrective steps be employed:

   (1) Perform measurements in critical frequency bands during hours when
   broadcast and other radio stations are off-the-air and ambients from
   industrial equipment are lower.

   (2) Insofar as is possible, orient the axis of an open area test site
   to discriminate against strong ambient signals.

   (3) Vary the bandwidth of the measuring instrument to separate ambient
   EME from emissions from the EPIRB.

   (b) Temperature. Except as otherwise noted, the ambient temperature
   during testing is to be within the range of 4 to 35 °C (40 to 95 °F).