§  2.1515   Spectral measurements.

   (a) Set-up. Spectral measurements are to be performed in a shielded
   room.

   Step (1) Place the EPIRB directly on a metal ground plane, such as the
   shielded room floor. The EPIRB should be powered by its own internal
   battery with its standard antenna attached and deployed.

   Step (2) Place a suitable receiving antenna at a convenient distance
   from the EPIRB and connect it to the input of the spectrum analyzer to
   observe the radiated signal from the EPIRB. A signal generator and
   frequency counter capable of operating at 121.5 and 243 MHz are also
   required for these tests.

   (b) Occupied bandwidth test.

   Step (1) Activate the EPIRB and observe the fundamental frequency on a
   spectrum analyzer. Adjust location of receiving antenna and spectrum
   analyzer controls to obtain a suitable signal level (i.e., a level
   which will not overload the spectrum analyzer, but is far enough above
   the noise floor to allow determination of whether or not the sidebands
   are attenuated by at least the amount required in the rules).

   Step (2) Set spectrum analyzer controls as follows:

   I.F. bandwidth: 10 kHz

   Video filter: OFF or as wide as possible

   Scan time: 100 ms./div.

   Amplitude scale: 10 dB/div.

   Scan width: 20 Hz/div.

   Center frequency: 121.5 MHz

   Step (3) Record the signal level in dbm.

   Step (4) Calculate the mean power reference level by adding 10
   log[10](D), where D is the modulation duty cycle determined in section
   2.1513(d) of this part, to the recorded signal level.

   Step (5) Set spectrum analyzer controls as follows:

   I.F. bandwidth: 100 Hz

   Video filter: OFF or as wide as possible

   Scan time: 10 sec./div.

   Amplitude scale: 10 dB/div.

   Scan width: 20 kHz/div.

   Step (6) Check the modulation sidebands for compliance with the
   required attenuation below the mean power reference level specified in
   § 80.211 of the rules.

   Step (7) Record how the test was performed, instrument settings and the
   occupied bandwidth in kHz and the 3 dB bandwidth of the carrier in Hz.
   (See § 2.1517 of this part).

   Step (8) Repeat Steps 1 through 7 for the signal at 243 MHz.

   (c) Signal enhancement test. The setup specified in § 2.1515(a) is to be
   used in this method of measuring signal enhancement. Other methods may
   be used if shown to give results equivalent to or more accurate than
   this method.

   Step (1) Activate the EPIRB and locate the carrier frequency at 121.5
   MHz on the spectrum analyzer. Adjust location of receiving antenna and
   spectrum analyzer controls to obtain a suitable signal level (i.e., a
   level which will not overload the analyzer, but is far enough above the
   noise floor to allow sidebands at least 40 dB below the carrier to be
   viewed).

   Step (2) Set the spectrum analyzer controls as follows:

   I.F. bandwidth: 10 kHz

   Video filter: OFF or as wide as possible

   Scan time: 100 ms./div.

   Amplitude scale: 5 dB/div.

   Scan width: 10 kHz/div.

   Center frequency: 121.5 MHz

   Step (3) Record the amplitude in dBm.

   Step (4) Calculate the total power output by adding 10 log(D), where D
   is the modulation duty cycle determined in § 2.1513(d) of this part, to
   the recorded signal level.

   Step (5) Set the spectrum analyzer controls as follows:

   I.F. bandwidth: 60 Hz or less

   Video filter: OFF or as wide as possible

   Scan time: 10 sec./div.

   Amplitude scale: 5 dB/div.

   Scan width: 20 Hz/div.

   Center frequency: 121.5 MHz

   Step (6) Measure and record the carrier power dBm as displayed on the
   spectrum analyzer.

   Step (7) Calculate the ratio of carrier power to total power from Steps
   4 and 6 using the following formula:
   [ec03jn91.004.gif]

   View or download PDF

   dB[C]= carrier power in step 6

   dB[T]= total power in step 4

   Step (8) Record instrument settings, sample calculation and the percent
   of power within ±30 Hz at 121.5 MHz or ±60 Hz at 243 MHz of the carrier
   frequency.

   Step (9) Repeat the above measurement Steps 1 through 8 for 243 MHz.
   For the higher frequency, the I.F. bandwidth in step 5 must be 120 Hz
   or less.

   (d) Carrier frequency test. The setup specified in § 2.1515(a) is to be
   used in measuring the carrier frequency.

   Step (1) Activate the EPIRB and locate the 121.5 MHz signal on the
   spectrum analyzer. Adjust location of receiving antenna and spectrum
   analyzer controls to obtain a suitable signal level.

   Step (2) Set the spectrum analyzer controls as follows:

   I.F. bandwidth: 100 Hz

   Video filter: OFF or as wide as possible

   Scan time: 10 sec./div.

   Amplitude scale: 10 dB/div.

   Scan width: 20 Hz/div.

   Center frequency: 121.5 MHz

   Step (3) Combine the output of the signal generator with the EPIRB
   signal at the input to the spectrum analyzer.

   Step (4) Adjust amplitude and frequency of signal generator output to
   determine center of carrier frequency component.

   Step (5) Measure signal generator frequency with frequency counter with
   accuracy of 5 PPM or better and record as carrier frequency.

   Step (6) If applicable, change the type of modulation of the EPIRB and
   record the shift in carrier frequency as observed on the spectrum
   analyzer display.

   Step (7) Repeat the above measurement Steps 1 through 6 for 243 MHz.

   [ 56 FR 11683 , Mar. 20, 1991;  60 FR 47302 , Sept. 12, 1995]

Data Recording/Reporting Requirements