Technical Practices for LBA Technology AM Tuning Products – Application Note 20

LBA Technology, Inc. endeavors to fabricate AM tuning system products that are well balanced between state of the art technology and the most cost effective value to the customer. In most cases, products are customized to specific customer requirements. Unless agreed otherwise, products are fabricated in general accordance with the LBA standards set out below, adapted in the best judgment of LBA to the functional requirements of the product. Customer input is always welcome in the specification process.

Specification Summary:

Frequency: Apply from 530 – 1710 kHz

Power: Typically apply up to 100,000 watts

Load impedances: Customer furnished, if not, LBA best estimate

Input Impedance: 50 ohms (50 ohms also assumed for phasor – ATU cabling in directional systems)

Coaxial connectors: Flex foam coaxial cable interfaces are assumed. Cables to and including 7/8” will terminate to an LBA clamp. Above 7/8” to 3” will terminate to a 1 5/8” EIA flange/ clamp combination, and above 3” to a 3 1/8” EIA flange. Type N interfaces for sample cables. All cable terminations and cables are by others.

Control systems: Cabinets have safety interlocks on operator access doors and panels above 1 KW. Directional systems have remote-capable switching between day and night modes, and main and auxiliary transmitters. Control system typically uses 24 volts DC, and phasor/ATU contactors use 110 volts AC. Controllers normally mount external to phasors in customer racks. Control cables by others.

RF Current meters: Plug-in thermocouple meters, toroid meters are available options.

Lightning protectionAdjustable arc gap at output of ATU's and static drain choke for series towers.

Connection to ground system: Copper strap termination provided (2” to 5KW, 4” to 100 KW).

Tower lighting isolation: Where specified internal to cabinets, a 3 wire lighting choke rated to 120 volts AC, 20 amps will be supplied with cable access through a hollow output insulator stud.


General: The mechanical layout of RF components will comply with LBA standard construction practices. Long leads and unnecessary coupling between components will be avoided.

Typical component voltage and current design factors applicable to LBA-designed systems are set out in LBA Application Note 11: Vacuum and Mica Capacitor Inductor Ratings. For LBA designs, sufficient adjustment range will be normally provided in components to accommodate load impedances +/-20%. Customer furnished designs will be fabricated in accordance with customer specifications without liability to LBA for ultimate performance.

Inductors: RF Inductors will be arranged as practical to minimize mutual coupling. Where feasible, inductors will be spaced at least one radius from the cabinet. Inductors and interconectors under 80 amps are normally copper. Silver or tin plate is used on contact surfaces of non-plated conductors. Silver or tin plate is available as an option.

Capacitors: Mica capacitors will be employed unless otherwise specified, or unless vacuum capacitors are required to meet  LBA's specified design parameters.

Dielectric Materials: High arc resistant and dielectric strength suitable for 3.5 times design carrier voltage at 125% modulation.

Enclosures: Phasors will be housed in a LBA standard floor mounted indoor cabinet, typically, with off-white paint and blue trim.

Tower-base located assemblies such as ATU's, diplexers, and filters are in weather resistant aluminum cabinets for outdoor mounting. Mountings are by others. Cabinet are unfinished aluminu with exterior paint in off-white with blue trim as an available option.

Cabinets are typically provided with lift-off doors with quick release fasteners. Locks are an available option.

Screened cabinet air vents provide convective flow for component cooling.

Environmental: Temperature: -10°C to +45°C outdoor, +10°C to +30°C indoor at 95% relative humidity.

Documentation: Schematics, interconnection diagram (if required), and parts list to be included with shipment.

Services: Equipment is factory tested to assure compliance with basic performance requirements. Final tuning and operational adjustments are by others. Field services, custom tuning, and special testing are available options.

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About LBA

LBA Group companies serve technical infrastructure needs related to the broadcast, wireless, electromagnetic compatibility and safety sectors worldwide. We provide consulting, training and other telecommunications industry services. We also produce and market hardware for radio transmission, RF shielding, safety and testing.