Operating Conditions 



The if/am amplifier modules were operated with an input signal level of 

 1000 microvolts and a carrier frequency of 500(±3) kHz, modulated 30 percent with 

 a 1000-Hz tone. The supply voltages to the modules were held at +27 Vdc and 

 -27 Vdc by two regulated power supplies. The modules were adjusted for 1 milli- 

 watt of output power across a 600-ohm balanced load and the volume control wa* 

 locked to prevent alteration as a result of vibration. 



Performance Measurements 



Performance measurements were recorded for each of the 27 treatments 

 that were applied to the test specimens. These measurements consisted of the 

 voltage at three test jacks, output power, and distortion. Prior to each run, a set 

 of initial readings was taken at room ambient condition for each of the three test 

 specimens. 



Test Conditions 



A three-factor, three-level, full-factorial test which consisted of 27 com- 

 binations of temperature, humidity, and vibration was applied six different times 

 to each test specimen. Each of the 27 treatments was allowed to stabilize for 1 

 hour to expedite the complete test. Stabilization was verified by monitoring wet- 

 and dry-bulb charts and by monitoring the internal temperature of each module with 

 thermocouples. After the elapse of an hour, performance measurements were re- 

 corded for each specific treatment. In the interest of repeatability, the tempera- 

 tures and humidity levels were programmed from two cams. The 27 treatments 

 along with levels of the three environments are shown in table 1. 



