Garage Door Opener Radio Interference (and fix)

Our garage openers are both Linear LDO50 which uses 318MHz frequency for the receiver, and are about 12 years old. The security type is “MegaCode”.

We live directly across from a major airport, and not far from a smaller airport, so we typically get a LOT of radio interference with our garage openers. I can often see the receive indicator on the openers glowing solid red, or blinking rapidly for several seconds at a time. This causes the door to open slightly and then stop, and this repeats several times. Some days I just had to get out of the car and use a key to get in through a side door. The wall buttons for the openers always work, so I know there is no physical issue with the openers.

So I decided to try adding a new receiver that uses “Security+ 2.0” and 3 simultaneous frequencies (310/315/390MHz) since it is unlikely that all 3 will be getting interference at the same moment.

I bought the Liftmaster 850LM receiver that can control up to 3 openers. I also bought the compatible Liftmaster 892LT two-button remote controls.
NOTE: The remotes are able to use three different modes, and you must choose which one you will use.

1. I first set each remote control to use Security+ 2.0 instead of just 315Mhz or 390MHz.
Remote control

2. I plugged-in the receiver and pressed the Learn button for Channel 1 until the yellow LED turned on. I then pressed the left button of the first remote control to associate it with Channel 1 of the receiver. I repeated the process for the second remote. (Channel 1 can support up to 50 different remote controls! Channel 2 & 3 can each support up to 20 remote controls.) I then did the same for Channel 2, this time using the 2nd button on the remote.

3. I attached the receiver to the angle iron that holds the first garage door opener motor. I plugged in the power adapter and tied up the slack in the wires.
1st unit wiring

4. I used common telephone cable to do the wiring. I only needed 2 wires to each opener, so I cut off the remaining wires. I chose at random to use Blue and White. I chose to use Blue as the “common” and white for the other. No electricity is passing through these wires, it is simply providing “continuity”. That is, when the receiver gets an authorized signal, it essentially closes a switch that connects the two wires. The garage opener senses that the two wires have touched and opens or closes the door.
Receiver wiring
Closeup of receiver wiring

5. I stripped the ends of the wires and attached a short piece of cable from CH1 of the receiver to the Pushbutton and Common terminals on the first opener. I stapled the cable to the ceiling using curved staples for wires.
Closeup of opener wiring

6. I did the same steps to connect CH2 of the receiver to the common and pushbutton terminals of the second opener, this time using a 20ft piece of cable.
2nd unit wiring

That’s all there is to it. I tested each button on each remote and the doors opened and closed as expected.

I then erased the memory of the built-in receiver in both Linear units, and gave one of the new remotes to my wife, and took the older remotes, removed the batteries, and stored them in a box. Time will tell if this solution works well.

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