AM Antenna Tuning Units (ATU's)

LBA medium wave AM Antenna Tuning Units (ATU) and Line Tuning Units (LTU) are impedance matching units designed to match the transmitter to the impedance of the transmission line or the antenna system. Our Antenna Tuning Units are available for both series-fed and Tunipole antenna systems Tunipole™ antenna systems to powers in excess of 500 kW.

Closely related to Antenna Tuning Units are AM multiplexers (diplexers, triplexers, and quadraplexers) used to combine multiple transmitters into a single antenna. These combine ATU’s with RF filters. You can find more on LBA AM RF multiplexers here. Antenna Tuning Units are also major subsystems of AM directional antenna systems . More on LBA AM directional antennas here.

LBA AM transmitter to antenna matching systems are available to meet performance requirements of IBOC and DRM digital systems, or to any customer broadband requirement. Existing antenna tuning systems can frequently be upgraded for digital operation through the addition of properly designed phase matching units.

Every antenna tuning unit (sometimes called Antenna Coupling Units) must be designed to conform to the particulars of the AM antenna and transmission system. We work closely with you to determine the specific requirements of your system.

Some of these design considerations include: transmitter power, frequency, bandwidth, antenna impedance, safety margins, stability, operating environment, enclosures, and personnel RF safety. Thus, you can see that a 1000 watt ATU may be quite straightforward and its small enclosure easy to install, whilst a 500 KW ATU may involve not only electrical design, but architectural, structural, and shielding considerations as well – to say nothing of taming high voltages!

Most AM broadcast ATU systems are designed for a single medium wave transmitter frequency. However, LBA has designed and furnished frequency agile Antenna Tuning Units for use across the 0.5 – 1.7 MHz band, as in our transportable AM antenna systems. We have also designed and built other specialized Antenna Tuning Units, such as the dual frequency ATU used in NAVTEX navigation antenna systems.

Generally ATU’s, regardless of power, are made of Pi-networks, T-networks, or L-networks. T-networks are almost universally used in systems to 25 KW or so for their versatility and economy. At higher powers, many engineering economy and component practicality considerations come into play, so the designs of these ATUs become more complex. Conservative design with Hi-Q components allows highly efficient, broadband, reliable operation under a wide range of environmental conditions, at rated power to 125% modulation or more.

Antenna Tuning Units to 100 KW are normally furnished in weatherproof enclosures or open panel, walk-in and custom cabinet arrangements.

LBA Antenna Tuning Units for higher power, or which include complex filter or switching systems, are typically designed as modular systems for field installation in customer provided buildings, or LBA modular buildings. This unique modular approach allows complete assembly and testing in LBA’s plant, easy customer installation planning, and very fast on-site commissioning.

We can supply our custom prefabricated buildings for high power ATU systems. These buildings use a rapid installation system that permits them to be fully knocked down for containerized shipment. They are foam insulated, incorporate RF shielding, can be furnished with full electrical systems to any local standard, and can include heating/air conditioning systems. Use of these buildings greatly shortens on-site commissioning. The building is set up and the Antenna Tuning System modules installed and tested at the LBA plant. The entire system is then marked and documented for fast assembly at the customer site before being containerized for shipment.

A variety of accessories and options can be furnished for our ATU systems, or to upgrade or repair your existing system. These include mica and vacuum capacitors, high power components, RF inductors and coils, RF ammeters, tower insulators, lighting transformers, lighting chokes and cabinets.

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Accepted