§  2.1511   Measurements of radiated emissions.

   The Commission's Rules require that the peak efficetive radiated power
   (PERP) of a Class A, B or S EPIRB not be less than 75 mW under certain
   specified conditions. The PERP of an EPIRB transmitter is determined by
   comparing its level to a reference PERP generated by a standard
   quarter-wave monopole antenna located on a one wavelength minimum
   diameter metal ground plane. The Rules also require that all spurious
   and harmonic emissions be attenuated by a specified amount with respect
   to the reference PERP. In addition, there is a limit on the PERP of
   radiated emissions with the switch in the test mode. These measurements
   are to be made in accordance with the following procedure.

   (a) General set-up instructions. Measurements of radiated
   electromagnetic emissions (EME) are to be performed on the 30 meter
   open field test site described in § 2.1503(a) of this part and on one of
   the pair of frequencies listed in § 2.1507 of this part. A receiver,
   tuned dipole antennas and a calibrated signal generator as described in
   § 2.1505 of this part are required. The EPIRB should be powered by its
   own internal battery with its standard antenna attached and deployed.

   (b) Set-up for radiated EME tests.

   Step (1) Place a 121.5 MHz quarter-wave vertical antenna element at the
   center of the ground plane and connect the output of the calibrated
   signal generator to the antenna.

   Step (2) Mount the tuned dipole antenna on the antenna mast, tune the
   elements to 121.5 MHz and connect the antenna to the receiver.

   Step (3) After an appropriate warm up, turn the receiver to the
   frequency of the test unit, set the detector to peak mode and the
   bandwidth to 100 kHz.

   (Note: It is sometimes helpful to monitor the receiver audio output
   with a speaker. The EPIRB signal may be identified by its distinctive
   modulation.)

   (c) Radiated EME tests.

   Fundamental emissions-peak effective radiated power

   Step (1) Turn on the signal generator and adjust the output to 75 mW at
   121.5 MHz.

   Step (2) Vary the antenna height from one to four meters in both
   vertical and horizontal polarization. Record the highest receiver
   reading in dBm as the reference level.

   Step (3) Disconnect the signal generator and replace the quarter-wave
   vertical element on the ground plane with the EPIRB under test. The
   EPIRB is to be positioned directly on the surface of and in the center
   of the metal ground plane.

   Step (4) Activate the EPIRB.

   Step (5) Vary the receive antenna height from one to four meters in
   both vertical and horizontal polarization. Record the highest receiver
   reading in dBm and the instrument settings, antenna height and
   direction for maximum radiation, antenna polarization and conversion
   factors, if any, associated with that reading.

   Step (6) Repeat Step 5 with the EPIRB switch in the test position.
   Return the switch to the normal operation position.

   Step (7) Rotate the EPIRB 30 degrees and repeat Steps 5 and 6. Repeat
   this step for all successive 30 degrees segments of a full, 360 degree
   rotation of the EPIRB.

   Step (8) Repeat § 2.1511(b) and Steps 1 through 7 for 243 MHz.

   Step (9) Compute the peak effective radiated power for the maximum
   level of each measured emission using the following formula:
   [MATH:  :MATH]

   where:

   dBm[meas]is the measured receiver reading in dBm, and

   dBm[ref]is the reference receiver reading found in step 2 of
   § 2.1511(c).

   Step (10) Record the PERP in mW. The FCC limit for minimum power in the
   normal operation mode (i.e., with the EPIRB switch in the normal
   operating position) is 75 mW. The FCC limit for maximum power in the
   test mode is 0.0001 mW.

   Spurious emissions

   Step (11) Reset the signal generator to operate at 121.5 MHz.

   Step (12) For each spurious and harmonic emission to be measured,
   retune the receive antenna to the appropriate frequency and repeat
   Steps 5 and 7.

   Step (13) Determine the FCC limit on power for spurious emissions on
   the frequency of each measured emission as follows:

   The rules require that spurious emissions be attenuated at least 30
   decibels below the transmit power level. Therefore, the maximum
   received power limit for a spurious emission can be calculated from the
   formula:

   dBm[spur]= dBm[meas]+AF[121.5]−AF[spurfreq]−30

   where:

   dBm[meas]= measured receiver reading (Section 2.1511(c), step 5).

   AF[121.5]= tuned dipole antenna factor at 121.5 MHz.

   AF[spurfreq]= tuned dipole antenna factor at spurious freq.

   Step (14) Record in dB below the fundamental emissions the level of all
   spurious and harmonic emissions within 10 dB of the FCC limits.