The U.S. Army AN/TRN-30 non-directional radio beacon set transmits a homing signal that is detected by airborne direction finding sets installed in selected aircraft. The system was first fielded in 1971. There are approximately 160 aging Radio Beacon sets that must be sustained for another 15 years, until they are planned to be replaced by GPS based systems. Neither original manufacturer of the equipment is still in existence. Currently, the depot-level overhaul work of both systems is being performed by Tobyhanna Army Depot.

The benefits of using the EMPF for the re-design/upgrade of this equipment include use of its component engineering and SMT manufacturing expertise to replace obsolete through-hole SN54xx small-scale integrated logic parts used in the existing Radio Beacon sets. Also, the high power operation of the Beacon will require extensive thermal analysis which can then be verified in-house by HALT, HAST and thermal cycling tests.

The radio beacon set provides an AM radio frequency signal on any one of 964 channels in the frequency ranges from 200 kHz to 535.5 kHz and 1605 to 1750.5 kHz. The radio frequency output is modulated by a 1020 Hz tone, which is automatically keyed to form Morse Code characters in four-letter groups. The radio beacon set is used in one of two modes, pathfinder, tactical/semi-fixed. In pathfinder mode, the transmitter, battery and antenna are back-packed until a suitable location for a temporary airfield is found. In tactical/semi-fixed mode, the amplifier-coupler is delivered by helicopter to a semi-permanent airfield site where it is powered by a generator and broadcasts at 60-180 watts to a range of 50-100 nautical miles using a 30 or 60 foot antenna.

There have been many equipment functional failures related to a combination of material, process, and design issues. The Operation Readiness (OR) rating of the radio beacon sets is now in jeopardy of falling below an acceptable level. Also, the current state of supporting documentation (drawings, specifications, inspection and test criteria, etc.) exacerbates the difficulty in troubleshooting and repair of the units as they are serviced. A strategic goal of CECOM is to maximize the readiness of this equipment by improving its reliability, availability, and maintainability, while also reducing the total ownership costs.

EMPF engineers attended a Beacon value engineering workshop with personnel from CECOM, Tobyhanna Army Depot, and Fort Rucker. The resulting ideas were categorized in the following areas:

(V1): Transmitter, Radio Assembly T-1199 / TRN-30(V)
1. Variometer component failures
2. Rotary switch failures
3. High voltage arcing of wires within V1 chassis
4. Morse Code, (26) position, alpha selection switches/ obsolete part
5. Seals and gaskets (to prevent water leakage) on V1 chassis hardware
6. DC drive gear-case motor failures / obsolete part
7. Motor drive-shaft coupler alignment failures
8. Negative 8 volt DC regulator / obsolete part
9. Wire harnesses / pinched wires

(V2): Amplifier Coupler Assembly AM-6417/TRN-30(V)
1. Helix/wiper/servo inductor assembly in antenna coupler unit
2. DC drive gear-case motor failures / obsolete part
3. Motor driveshaft couplers
4. Transformers in the RF amplifier assemblies: failures / obsolete part

The outside mechanical housings (chassis) of the radio transmitter and amplifier-coupler units will remain essentially unchanged. This will ensure form, fit, and functional equivalency between the current and upgraded beacons. Also, compatibility will be maintained with all existing beacon accessories such as cables, connectors, antennas, power sources, transport cases, etc.

The benefits to the warfighter will be improved availability, reliability and maintainability. Use of current technology will reduce both weight and cost. The ability to accept GPS co-ordinates into the Beacon will be designed-in as a future potential improvement.

Functional areas that are likely candidates for upgrading were identified. Modern COTS modules for the power supplies, linear RF amplifiers, and stepper motor drive systems were implemented. For the sake of expediency and cost effectiveness, both short and long term, some of the existing, unique components and subassemblies may be retained as is, or repair and refurbishment procedures will be developed and documented.

An embedded general purpose microcontroller with subroutines and algorithms implemented in firmware, will replace practically all of the discrete, low power logic (currently located on the eight (8) PCB assemblies). This will result in considerable space savings within the V1 chassis thus permitting a re-dressing of the high voltage cables for proper spacing (and elimination of the wire arcing problem). The problem of the obsolete, out-of-production -8 volt regulator IC was solved by use of +5, -5 and +12 volt supplies only.

Another critical design direction will be the replacement of the failure prone mechanical “tuning” servo system that has motion and alignment problems associated with the selection of switched filters. High-voltage vacuum dielectric relays will be used in their place, and activated under control of the microcomputer. This will resolve the single biggest complaint with the existing design.

In 1969, it was common to use mechanical, non-illuminated switches for both alpha and numeric entry and display. These switch assemblies were bulky and typically required a diode matrix to decode their setting. The 27 position alpha displays used to set the 4-letter Morse Code message are no longer manufactured. The EMPF re-design / up-grade will use 7-segment red LED alpha 4 character displays to show the message. The value of the message will be stored in non-volatile memory so that if power is interrupted, the previous message can be automatically restored.

The existing Beacon design employs switched LC filters in both the transmitter and amplifier-coupler. These filters convert the square wave generated by the digital logic into a sinusoid suitable for broadcast from the antenna. There are 5 filters in the transmitter and 4 in the amplifier coupler. Problems with the servo motor and associated gearing and linkage comprise one of the more common failure modes of the Beacon. The re-design/upgrade eliminates the need for these moving parts by using a linear RF amplifier in place of the Class-S switching amplifier design. This approach eliminates the need for many electronic and mechanical components. Thus, the new Beacon will be more rugged, reliable, lighter and more affordable.

The re-designed Beacon will have far fewer printed circuit boards and fewer total electronic components. Instead of soldering wire directly to E-terminals, board connectors will be used. There will be fewer total wires and more room to make gentler turns with them. The standards and procedures of IPC/WHMA-A-620 Requirements and Acceptance of Cable/Wire Harness Assemblies will be used in the construction of the re-designed Beacon.

In conclusion, the Navy’s Center of Excellence is engaged in a re-engineering effort of aging electronic gear to extend its life, improve reliability, and make it maintainable for 15-20 more years. Field testing at Fort Rucker this coming summer will verify the success of our efforts.