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Cable Specs & Antennas

Cable Specs & Antennas #

To find its way to its destination and communicate with air traffic control and/or other aircraft, an airplane uses a variety of radio frequencies and cable specs are a part of it. The onboard radio equipment uses several sizes and types of antennas, each one created for a specific frequency band, to accomplish this successfully and cable specs help explain how all of it operates. Each of these antennas has unique frequency and application properties, as well as positioning on the aircraft. There are requirements for even the connection between the antenna and the avionics. A spherical coaxial cable and several connectors are often used for the connection. Purchasing high-quality cables will ensure that communications are clear and that cable losses are kept to a minimum, this enhances security.

Antenna Cables #

The antenna and aircraft radio are connected by a specialized connection with cable specs in mind. The radio and antenna must be compatible with the circular coaxial (coax) cable since it has unique properties for the frequencies employed (electrically and mechanically). It must not pick up signals like ignition pulses from the engine(s) or strobes or attenuate the signals too much and radiate within the aircraft.

RG-58 or Better #

Coax RG-58A cable is typically utilized for this, but not necessarily for this situation. The signal qualities at 100 MHz and above are not the best in the world, however this cable is thin (simple to handle and inexpensive). Please choose the cable specs RG-58C/U mill standard, or even better, the Aircell 5 or the golden RG-400, if you do need to use such a cable. Even though the cable impedance is 50 ohm, it has far less loss than RG-58A does. If you choose the RG-58 kind, only use it for incredibly short runs. Just a few feet, maximum. Only low power transmissions and frequencies below 30 MHz are practical for using RG-58A.

Impedance and cable signal loss at particular frequencies and lengths are characteristics of coaxial cable. The characteristic impedance of standard coaxial cable used at aircraft frequencies (VHF and UHF) relies on the dimensions of both conductors, and cable loss is influenced by the size of the conductor in relation to the type of dielectric used (dielectric is the material isolating the two conductors inside the cable, which can be air or some kind of foam).

A Good Antenna Cable #

Saving money on the connection that connects your radio and antenna usually means sacrificing clear communication over long distances, whether you are broadcasting or receiving. Do make the purchase of a high-quality cable. The LMR-400, AIRCOM plus, or CLF-400 are the models that would be advised. In between these cables, an RG-58C/U mill specification, and Aircell 5, RG-213/U would be an affordable substitute.

Top- notch Cables #

These cables are the best because they have almost no signal loss at VHF/UHF frequencies and can be used for your transponder with equal performance on UHF (950-1050 MHz). They are about 10 mm thick (RG-58 and Aircell 5 are 5 mm diameter), have a sturdy connector, and do not bend as easily as the thin types. Use the RG-58A to try that. Ever ponder why ATC could occasionally declare: “No radar contact”? In general, a thicker cable will result in less signal loss while transmitting or receiving.

Keep the antenna wires apart from other cables while putting them in the aircraft. As a result, there is less chance that RF power will be transmitted through other aircraft wiring and that the intercom system will pick up or hear strobe pulses. Additionally, avoid kinking the wire and fitting it too firmly into the fuselage’s structural corners. Over time, the performance of the cable will decline as a result of these kinks since they might cause splits in the braided shield and outer jacket. Keep in mind to check the cable of your choice’s minimum bend radius criteria.

Balun #

This will not produce a perfect match because the coax cable from the cable specs is asymmetrical and the dipole antenna (VOR) is symmetrical. When these two are connected, the coax cable will function as an antenna, receiving or radiating signals rather than blocking them. Both inside and outside the aircraft. A transformer, known as a “balun,” must be employed to solve this issue. “Balun “is also short for balanced-unbalanced.

Sometimes the antenna comes with this balun according to cable specs. However, you can save about $60 if you purchase one without the balun. You may create your own balun using high-quality coax, such as Aircell 5 or RG-400 cable, for that amount of money. The antenna and balun should be connected to the VOR receiver using the same connection. You’ll even have enough money left over to buy yourself a beer!

Building a Balun (Pawsey Stub) #

With an RG-58C/U cable and tuned for 113 MHz (the middle of the NAV band), the balun’s computed length is 45 cm, or 17.7 inches. Details can be found in the formula through cable specs inspection. You must shield this balun from the elements with insulation tape, heat shrink tubing, and some weather- and UV-proof sealant in order to make it sturdy. Make sure to adjust the calculation if you use a cable with a different velocity factor. Replace the .68 in the formula with the velocity factor of Aircell 5, for instance, and you’re ready to go.

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