Garage Door Openers: A Short History – Part II “RFI (Radio Frequency Interference)”

Garage Door Openers: A Short History – Part II “RFI (Radio Frequency Interference)”

Note – this is the 2nd installment in this series. To read the first and last, click on these links:

Garage Door Openers: A Short History – Part I
Garage Door Openers: A Short History – Part III Technology That Means Something


Northwest Door & Operators Association

Just recently we got back from the Northwest Door Association’s 2013 Regional Trade Show in Portland.  It is fun to keep up on the latest innovations in the Garage Door business but I like going there for the educational classes.  When I take a class on things I have been working on for years I love to find those little “nuggets” of information that make the classes pay for themselves.

One class I took was taught by our local representative from Linear Corporation.   Mike is quite a character and he made it fun.  It was titled:  RADIO FREQUENCY ISSUES.  Linear Corporation was a pioneer in the area of radio sets for Garage Doors and is still a leader in the industry.  In the past many of the big Garage Door Operator manufactures used radio controls made by Linear but now make their own.

In order to comply with FCC (Federal Communications Commission) rules and regulations Garage Door radios are to have limited power and therefore limited range.  They are on the bottom of the food chain in the world of licensed radio controls and the transmitters, or remotes, are not allow to give interference to any other devices.  Every time the FCC decides to change the rules for what radio frequencies allowed, the Garage Door Manufacturers are scrambling to try to solve the problems.

Garage Door Operator receivers can’t respond to more than one signal at a time and are often blocked by devices that emit signals on or near the same frequencies as their remotes.  What that means to you is that when you have to get closer and closer to your Garage Door before the remote will work it may not be a problem with your Garage Door Opener but an interference problem.

Before I start looking for RFI (Radio Frequency Interference) I always check the battery on the remote.  Even if you recently replaced it it’s worth a try.  I can’t tell you how many batteries I have found that have just come from the store and are dead, so check it anyway.

One of the big indicators of RFI is if several activation devices are having the same problem at the same time.  Remotes, Keypads and Home Link buttons built into the cars all work by transmitting radio signals.  If the operator still works by the wall control button but not remotely it is usually a failure of the radio receiver or radio interference.

The next thing I do is to check the antenna that hangs down from the motor head.  It is attached to the radio receiver.  More than one customer has decided to cut off this funny looking loose wire and suddenly has no range on their transmitters.  Just hanging straight down is usually the best scenario and not the way people curl them up like little piggy tails.

I also like to check connections on all the wiring to the Garage Door Opener to be sure that they have not corroded over time.  You would be amazed at how many corrosive chemicals there are in garages from fertilizers, insecticides, herbicides, paints and paint thinners etc.

Radio receivers do go bad but before you spend the money to buy a new circuit board which usually includes the receiver components look to see if there are any obvious sources of RFI.

The Door Works RFIThere are any numbers of things that can interfere with your Garage Door radios.  It’s a good thing we can hear only a limited range of audio frequencies (20Hz to 20,000Hz) because if we did hear everything in the radio frequency range we would be going crazy because the list of things that emit radio noise is getting longer and longer every year. These are only a few that commonly interfere with garage door openers:

  • Nearby airports
  • Television or Radio transmission towers – the ones on Queen Anne hill are notorious for sucking the life out of Garage Door Opener range.
  • Military Installations and ships cruising up and down the sound and ship canal
  • Power Lines
  • Cell Phone towers
  • Appliances within 10’ – 15’ of the receiver whether they are running or not.  Mike found a microwave in a garage door that wasn’t even plugged in that gave off enough interference to keep the operator from working.
  • Plug in transformers like the ones used for security systems, sprinkler controls, and cordless power tool chargers.
  • Wireless doorbells
  • Computers
  • Wireless networks/Wi-Fi
  • Fax Machines
  • Copiers
  • Cordless Phones
  • Yard light timers and motion detectors
  • Christmas tree lights.  Since people started decorating with LED (Light Emitting Diode) Christmas lights the calls in December complaining about reduced range on Remotes have gone up dramatically.
  • Any number of small appliances.  Searching online I found one of the most common culprits were cheap clock radios.
  • Air Conditioning or heating system thermostats
  • Florescent lighting fixtures
  • Halogen lighting fixtures
  • Ham Radio transmitters. One customer complained that between 4:00 – 6:00 pm each day her garage door wouldn’t work.  It took a few trips out and her asking around the neighbors to find out one of them was on his Ham radio at that time each day.
  • Car battery chargers
  • Motor Homes have all kinds of things that interfere.

Occasionally the RFI is coming into the garage by way of the house wiring because many houses have the circuit breaker boxes near the Garage Door Openers.

There are several things that can be done to figure out what and where the interference is coming from.  One way is trial and error, or simply moving suspect devices or turning them off one by one.  On most of the newer Garage Door Openers there is a little LED light next to the learn button on the back of the opener.  If you watch that little light while you push the button on your remote you will see it flash.  The flash is because it is hearing the radio signal from your transmitter (remote).  Sometimes there will be some flickering on that learn button light even when you aren’t pushing the button on your remote, that is because it is ‘hearing’ other radio frequency sounds.  These little indicator lights can sometimes be helpful in figuring out the problem when the interfering device has been turned off.

Linear has a handheld ‘Field Tester’ that can help you audibly hear the interference on the 318MHz frequency that they use.  It can be used by walking around the garage with it like Captain Kirk scanning a hostile planet.  Usually the closer you get to the source the louder the hissing gets.  When our field tester is on we can hear the sirens of fire trucks anywhere within a mile or so.  I haven’t got a field tester for the other common frequencies (300MHz, 310MHz, 390MHz and 228MHz) but I am looking for one.

Once you determine where the RFI is coming from the next challenge is to find the right fix for it.

Obviously if it is from an appliance that you can do without is to disconnect it.  If it is from a neighbor’s source you can’t just eliminate him.

There are filters that can be purchased that can reduce or eliminate RFI that is coming through power lines or telephone lines.  Some improvement can even come from common surge protectors.

Changing remote controls can sometimes make a big difference.  Some of the higher quality remotes operate on a narrower band and get around some of the RFI background noise.

Changing to radios that operate on different frequencies can sometimes help.  However there may still be RFI on the new frequency.  A coaxial antenna can be placed away from the RFI source with a shielded cable that runs to the operator might do the trick but not always because it may just get you closer to the interference source.

The best solution may come from newer technology from the major manufactures.  These are radio sets that transmit and receive on two or three different frequencies simultaneously.  The first to activate the door is acknowledged and the other frequencies are ignored.  It is less likely that radio frequency interference is coming across all three frequencies at once.

We will look at some of the innovations in Garage Door Openers in Part 3 of the history of Garage Door Operators.

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