Sec. 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

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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 
Sec. 2.1503(a) of this part and on one of the pair of frequencies listed 
in Sec. 2.1507 of this part. A receiver, tuned dipole antennas and a 
calibrated signal generator as described in Sec. 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 Sec. 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:
[GRAPHIC] [TIFF OMITTED] TC03JN91.001

where:

dBmmeas is the measured receiver reading in dBm, and
dBmref is the reference receiver reading found in step 2 of 
Sec. 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:

dBmspur = 
dBmmeas+AF121.5-AFspurfreq-30

where:

dBmmeas = measured receiver reading (Section 2.1511(c), step 
5).
AF121.5 = tuned dipole antenna factor at 121.5 MHz.
AFspurfreq = 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.

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