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Apr 08, 2003, 11:01 PM
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Adding Elevator Launch Preset to JR631 (Poor Man's DLG Transmitter)

Dear List,

I finally abandoned my efforts to add Flaperon, Flapervator, and Launch Preset to my old analog radio, in favor of something less time-consuming.

The JR631 is a relatively inexpensive 6-channel low-end computer radio, but it includes flaperon capability, with flaps on a two-position switch, perfect for camber control of an aileron DLG, like an XP-3, Enigma, or Taboo XL. Problem is, it lacks a launch preset capability, so one needs to use a forward CG to get a pitchup on launch, at the cost of both weight and launch height (since the pitchup is more gradual).

Fortunately, it's very easy to add an elevator preset button (and rudder preset, if you think you need it). It takes three components in series; a momentary normally open subminuature pushbutton, a 5k resistor, and a 100k audio-taper pot. This circuit is wired in parallel with the "up" side of the elevator pot. (See attached photo--please excuse my reaching the limit of my camera's macro capability. The close up is blurry, but the back's on the radio now, and I'm not up to pulling it off. The blur is a close-up of the wires connected to the bottom two terminals of the elevator stick pot.) I moved the gear switch inboard, as shown, and put the pushbutton in the gear position, just right for a right handed thrower.

The function is simple. When the button is depressed, the 5k-to-105k resistance is added in parallel to the 2.5k of the "up" half of the stick pot, resulting in up elevator udjustable to roughly the same range as the up trim control. When the preset button is released, the preset is completely out of circuit, and the radio behaves as designed.

Hope this helps someone else who doesn't want to pop $130 on a new RD8000 just yet. (I will next season.)

Peace to all,

Last edited by marctrudeau; Apr 08, 2003 at 11:17 PM.
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Apr 10, 2003, 09:48 AM
Gambler-AG DLG Designer
Allan Wright's Avatar
Great tip! Thanks Marc.

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