The premise of an automatic gate opener is to allow someone in and out of property through a gate without getting out of a vehicle. A sensor on the gate detects an approaching vehicle, the gate opens in anticipation, then closes when it senses the vehicle has passed through. With a few small alterations, you can extend the gate opener's range.
Locate the sensor's electrical box, which usually will be on one of two poles on either side of the gate. Open up the box carefully.
Examine the inside of the electrical box and locate the range adjustment board. It will be connected to the rest of the gate sensor with a black and yellow wire.
Look for the potentiometer on the range adjustment board. This is a dial directly on the board.
Turn the dial clockwise as far as it will go. This will increase the gate opener's range to the maximum supported by the hardware. The distance depends on the model.
Test the gate with the new settings. Dial the potentiometer down if the range is now too high. Find the distance that is suitable for the situation.
Replace the cover of the electrical box.
With the new range, anything that trips the motion sensor will cause the gate to open. Consider this when adjusting the range.