Boeing B737 - Fault Diagnosis and LED Indicators; Power Output and Frequency Tests

B737
MAINTENANCE MANUAL
EFFECTIVITY
Post ELT STC ST03081AT
23-24-00
PAGE 205
JAN 02/07
(10)
Audio Modulation
NOTE: The power output is approximately 37 dBm © 5 Watts. Ensure adequate attenuation is
inserted in-line between the ELT’s 406.025 MHz output and the input to the spectrum
analyzer to protect the analyzer’s input circuitry.
(a)
Connect the equipment as shown below:
(b)
Set the Spectrum Analyzer as follows:
1) Center Freq: 406.025 MHz
2) Span: 1 MHz
3) Resolution Bandwidth: 1 MHz
4) Vertical Display: 10dB/Div
5) Sweep: Auto
6) Peak/Avg: Peak
7) Reference Level: 30dBm
8) Time/Div: 20ms
9) Max Hold: On
10) Attenuator (as required) on Input
(c) Turn the ELT on and wait approximately 50 seconds for the 406.025 MHz transmitter
to turn on (transmitter sends out first signal at 50 seconds then every 50 seconds
thereafter). Determine the power output from the stored waveform.
(d) The 406.025 MHz power output should be 37dBm +/- 2 dBm (3.16 W min to 7.94 W
max).
(11)
Measure the 406.025 MHz Frequency
(a) Ensure that adequate attenuation rated for 406.025 MHz, 37 dBm and 5 Watts is
installed between the ELT’s 406.025 MHz output and the input to the frequency
counter to prevent damaging the frequency counter’s input circuitry.
(b)
Set up equipment as shown below: