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 by Bob Aberle |
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Moving along the menu, press MODE and you come to "REVERSE." This function will let you reverse any servo's direction. Press SELECT to choose the channel function you want to reverse (1 to 6), and then press + or - to select the "NOR" (normal) or "REV" (reverse) servo direction. Press MODE again, and the "D/R" (Dual Rate) function comes up. The menu keeps going in one direction, as in a loop. If you miss an item, keep pressing MODE until it appears again. Dual rate control applies only to channels 1 (aileron or rudder when flying with three channels) and 2 (elevator). The LCD screen will show CH 1 or CH 2, which you choose by pressing SELECT. Then you will see 100%, meaning that the control is set for "full," or maximum throw. Use the data-input - switch to reduce the control to something less than full. Now that AIL/ELEV D/R switch at the upper right comes into play. With it in the down position, you want your aileron or rudder and your elevator at full throw, or 100%. Move that switch to the upper position, and the reduced throw that you just set (something less than 100%) will appear. Keep in mind that the AIL/ELEV D/R switch affects the two channels at the same time on this transmitter; you can't separate the aileron and elevator functions. Dual rate control can be helpful on faster models. At takeoff and landing speeds you have the controls set at full, or 100%. During the flight, you can flip the D/R switch to the up position and the controls will be reduced somewhat, making the airplane easier to fly at high speeds. When pressing the SELECT switch while in this same D/R function, after D/R you will come to an added feature called exponential rate control. When you get to this function you will see a plus and minus sign and 0% on the LCD screen. If you then press the minus switch, you will see a negative number such as 5, 8, 10, 15, etc. These negative numbers make the initial servo movement less than normal. What happens is that the control response is slower or "softer" around the neutral position. By selecting that negative number, you can tailor the feel to suit you and your model. I realize that this sounds slightly complicated at first, but you will learn as you gain experience with the system. Keep in mind that with the T6EXA you can have dual rate and exponential rate together or you can have dual rate or exponential rate separately. The next menu item (press MODE) is EPA. This is available on all six channels. It is especially nice to have EPA on the throttle channel when using a fueled engine; it makes high and low carburetor adjustments so easy. With EPA you can set the servo control throw to the exact amount of control required. You can even set the elevator for more up than down or more right aileron than left. This is probably the best feature in a computer-radio system. It is the control function you will use the most. As you go through the menu and make control adjustments, your inputs are saved automatically in the computer each time you move on to the next menu item or if you turn the power off. Afterward, any time you call up that particular model memory position, the control inputs you made will be right there for you (stored in the computer memory). The next menu item is important because it involves the trim function. Each of the four main channels has a separate trim switch. On this transmitter the trim is the more modern digital variety. The purpose of trim is to allow you to set your model for straight and level flight with your hands off of the control sticks. You "rocker" the trim switches left or right or up and down to achieve level flight characteristics. Once you have a model adjusted for level flight, you can call up the "TRIM" menu item. It will allow you to select any one of the four channels that provide trim (aileron, elevator, rudder, or throttle). For each function the LCD screen will provide a numerical trim position. This is strictly for reference purposes. Remember that whatever trim you use on a particular model to achieve level flight will be stored in the computer and will remain until you make changes. On this particular transmitter, the fifth and sixth channel functions do not have trim. Also, on the CH 3 throttle function the trim only operates when the control stick is down close to minimum throttle. This is so you can set your fueled engine carburetor for the lowest possible idle speed yet not stall the engine. Frank Granelli will go into this feature. The remaining menu items cover certain mixing functions. There is a programmable mixing ("P.MIX") circuit that will let you combine any two control functions. I like to use this for coupled aileron and rudder on some models. When you apply ailerons to bank the model, the rudder will respond to that single command. Several wing-mix ("W.MIX") functions can provide such things as elevon control ("EL") that will mix aileron and elevator for flying wings or delta-wing models. The flaperon ("FP") function makes both ailerons drop down for flap-type control. A V-tail ("V") mixing function provides a rudder and elevator effect, as on a Scale Beechcraft Bonanza. I won't get into these mixer functions in any detail because you probably won't be using them right away. Quite a few computer-driven RC transmitters include multimodel-type programming; they offer menus specifically for fixed-wing aircraft, for helicopters, and in some cases for sailplanes. This makes for some difficult menu searching. Also, the switches are marked three ways, making identification difficult. I chose the T6EXA radio because it has one menu and is intended exclusively for fixed-wing aircraft. Many of these computer RC transmitters draw upward of 200 mA of current. It is still common to see 600 mAh-capacity Ni-Cd batteries supplied with these systems, but in today's hobby market we are seeing NiMH batteries in the same AA size with capacities up to 1100 mAh and more. Batteries such as these are available from suppliers such as Batteries America and SR Batteries. They even provide the mating connectors for your particular brand of transmitter. If you want more capacity with which to operate your transmitter for longer periods of time, these higher-capacity replacement packs are the way to go. Just remember from my "Battery Basics" article (in the October 2003 Model Aviation) that you must charge these batteries at the rate of C/10 (capacity divided by 10). An 1100 mAh battery would have to be charged overnight at 110 mA. To obtain that kind of current you will need a variable output charger, such as the Ace R/C Digital Dual Variable Charger. A number of computer transmitters currently on the market employ a synthesizer: a circuit that allows you to dial up any one of the 50 channels available for flying model aircraft. You can purchase the Hitec Eclipse transmitter with Hitec's Spectra synthesized module. This module plugs into the rear of the transmitter case. To change channels, you unplug the module and rotate two tiny dials to obtain any channel from 11 to 60. The Eclipse is also one of the transmitters that lets you select high or low FM deviation. That means you can operate any FM RC receiver on the market with this transmitter (regardless of the deviation or the channel number).
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