The Navy's very low-frequency, AN/FRT-95A 250-kW radio broadcast transmitters were difficult to maintain and seriously outdated. They contained obsolete components and required complex adjustments to keep them operating. The major problems that had to be resolved were their: control consoles contained hundreds of switch/indicators and thousands of unlabeled wires; 15 different designs of custom circuit card assemblies; use of mil-spec parts; and the ac power distribution equipment was populated with obsolete components including the main circuit breaker and surge suppressors. Additionally their technical manuals were of very poor quality and the original manufacturer of the control system had gone out of business.
Our engineers developed and fielded an entirely new control system built around a commercial, off-the-shelf programmable logic controller (PLC) and a touch-screen operator interface. Hi-Q worked with the solid-state amplifier manufacturer to develop an Ethernet interface for PLC control and monitoring of the power amplifiers, and wrote all of the embedded firmware for that interface. Hi-Q also configured, procured, and fielded a replacement ac power distribution unit, new ac power cable, and new cable tray installation. The resulting upgraded AN/FRT-95A transmitters feature:
- A single control cabinet that replaced three racks.
- Three custom circuit cards replaced the original 15 custom circuit cards that handle all of the RF signal processing, arc detection and protection.
- A single touch-screen interface that replaced 82 switches and 102 indicators.
- No maintenance alignments or adjustments - eliminated 100 trimpots.
- Comprehensive, on-line and off-line built-in-test of all control, monitoring, and fault protection circuits.
- Enhanced fault protection, including ground-fault protection for the amplifier output wiring.
- Fully automatic antenna tuning, loading, and power level control. Press the "ON" button and the system automatically tunes and matches the antenna, and then reaches the required radiated power, from any arbitrary turn-on condition without operator intervention.
- Graceful degradation - fully automatic reconfiguration of amplifiers to maintain the required radiated power in the event of an amplifier failure.
- A common control system architecture with the AN/FRT-72C transmitter, a 100kW version of the 95A.
- Fully redundant and fault tolerant fiber optic interfaces for all control communications between the Transmitter Control Console and the Antenna Matching System Control Console reducing intra-building single point failures and induced noise in the system's metering.
- Higher capacity and redundant ac surge suppression, higher ampacity ac power wiring, higher interrupting capacity power distribution equipment, true 50/60 Hz dual-rating for international use.