DEVELOPMENT OF LOCALIZER AND GLIDE SLOPE CLEARANCE TRANSMITTERS.
WILCOX ELECTRIC CO INC KANSAS CITY MO
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The report describes the design, development, and testing of prototype units of localizer and glide slope clearance transmitters for the Federal Aviation Administration. Where possible, subassemblies are interchangeable within and between transmitters. VHF signals are generated by a voltage-controlled crystal oscillator and doubler. An existing design power amplifier, with a unique low level modulation technique and over-current protection, was used. In the glide slope clearance transmitter, a tripler, with helical resonator bandpass filter, is used to obtain the required uhf signal. A constant impedance power divider is used to adjust output power level in the glide slope unit, but this is not practical for the localizer unit, so a technique of potentiometric scaling of ac and dc analogs of modulation and carrier levels was developed. Initially, due to the specified stability of plus or minus 100 Hz, it was necessary to use a phase-lock afc circuit, but relaxation of the specification to plus or minus 500 Hz allowed the use of the more simple discriminator. An extremely linear modulation detector is used to monitor percent of modulation. In addition to final performance testing, a feasibility test of afc lock-in of the clearance signals with modulated reference signal was conducted. It was found that the input signal level range permissable to give proper afc operation was considerably smaller than for the unmodulated carrier signal. Reliability analysis shows that both transmitters exceed the specified MTBF of 5,000 hours 8,693 hours for the localizer unit and 11,928 hours for the glide slope unit. Author
- Air Navigation and Guidance
- Radio Communications