Modern aircraft use a number of different types of electronic devices to support their operations. One such group is the various antennas that are used on board, including communication antennas, UHF antennas, NAV antennas, GPS antennas, marker beacon antennas, and emergency locator transmitter antennas. These antennas come in many different shapes and sizes, but they are often installed in similar ways. As such, much of the information we share in this blog can be useful for understanding the installation of antennas of all types. However, it is important to note that the following procedures are presented as examples only. One should always follow the specific manufacturer’s instructions when installing any antenna as an incorrect installation could cause equipment failure.
One common form of antenna is the typical rigid variety, and its installation process often involves these steps:
1. First, a template is placed on the fore-and-aft centerline at the desired location. This template will form a guide for drilling the mounting holes and correct diameter hole for the transmission line cable in the fuselage skin.
2. Next, a reinforcing doubler is installed to reinforce the aircraft skin so that it can properly support the new part.
3. Finally, the antenna itself is installed on the fuselage, and one should make sure that the mounting bolts are tightened firmly against the reinforcing doubler, and that the mast is drawn tight against the gasket. If a gasket is not used, a sealant such as zinc chromate paste can be used to seal the mast and the fuselage.
The mounting bases of antennas vary in shape and size, but the aforementioned procedure is typical of mast-type antenna installations.
Transmission Lines and Other Attachments
Most antennas are not isolated electronics, but rather are connected directly to an associated transmitter or receiver via a transmission line. Also known as a coax, transmission lines are shielded wires that are tasked with transferring energy from the antenna to its associated parts with minimal energy loss. While devices like transponders, DME, and other pulse type transceivers require transmission lines that are precise in length, other instruments may be more open to variation. For those that require a specific length, this value is usually the “critical length” of the transmission line, meaning that it is the maximum length at which there is minimal attenuation (energy or signal loss) of the transmitted or received signal.
To provide the proper impedance matching the most efficient power transfer, a balun may also be used in some antenna installations. A balun is a dipole antenna installation that is formed in the transmission line connection to the antenna.
Lastly, as with any form of cable or wiring, transmission lines must be installed using a form of connector. In this case, most transmission lines come within an installation kit that includes coax connectors. In some cases, the connectors may be pre-attached to the transmission lines, but an aircraft technician can also install these connectors on the coax when necessary. When installing coaxial cables, the cables are usually secured along their entire length at intervals of approximately two feet. To assure optimum operation, coaxial cables should not be routed or tied to other wire bundles. Additionally, when bending the coaxial cable, it is important that the bend is at least ten times the size of the cable diameter so that it is not damaged. Regardless, it is crucial in all cases to follow the equipment manufacturer’s instructions.
From using GPS to indicate the aircraft’s location to communicating with air traffic control, the various antennas on aircraft play an important role in fostering a safe and smooth flight. If you are an aircraft owner or operator in need of bearings, fasteners, IT hardware parts, or other aircraft components, NSN Catalog is ready to support you with your fulfillment needs. As a leading distributor of aircraft components that have been tested for their durability and authenticity, you can rely on our inventory of over 2 billion offerings. Begin procuring the parts you need from our team of market experts when you submit a Request for Quote (RFQ) form on any item(s) of interest. With representatives on standby 24/7x365, you can expect a custom solution to your parts needs in 15 minutes or less!
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