Garage Door Opener Mystery

1) Area 51 is expanding.

2) Can you here me now?......... Can you here me now?

3) I thought there was talk of some large solar flares. Is the dead zone gone now?

Will see in the morning if the problem is still there.

Hi

I heard half of amazing story this morning.

A man bought or were given a pair of sunglasses by a street vendor. He somehow got suspicious and eventually broke the pair to see what is inside.

It had a solar charger, battery and a small chip. Someone told him the chip was similar to the ones used by the satellite tracking systems. Apparently the syndicate could trace the whereabouts of the car.

It would be easy for a chip to record the pushbutton signals verify code hopping techniques because of the multiple tries and open the car with another signal via the chip at a later stage.

Did you buy a pair of imitation xxxxx recently?

Is there a sonic motion detector or pest repeller operating nearby. If the garage door was open during the problem, that might be the source of the "jamming".

I would suggest that the vechiles next to yours were jamming you processor with a signal that stop you from using the remote. I beleve most systems have a processor that turns off the remotes after several hits by an unkown signal. This then is reset after the vechile is started with a key.

So, the best CR4 can come up with is solar flare, fake eye glasses, sonic motion detector or a bug repeller.

We closed the garage door with the button on the wall. It made no difference to the problem. It is an automotive machine shop. I have been working there for over 30 years and there or ANYWHERE else, I have NEVER seen jamming done like that.

Once we moved far enough away from the center of occurrence, our vehicles parked side by side within two feet of each other had NO PROBLEMS. The clickers worked fine. No matter how many times Jason clicked his, mine still worked.

Your car is in the center of a parking lot. NOTHING around you for 50 feet in any direction, and you walk up to your car and the clicker will NOT operate. You open the car, start it, push the buttons. Nothing. Move the car a few feet and then the opener/clicker works. Move the car back where it was, doesn't work. Do you look around for fake sunglasses? A solar flare? A bug repeller?

It was confined to a small area, just several hundred square feet where they would not work.

Everything works okay again today. Why didn't it work yesterday. We never changed anything.

I don't know if jammers can be directional, I would suppose so. There is a restaurant next to us, an auto parts store across the street and an auto repair shop on the other side of us about 70 feet away.

There is a cell tower behind us 100 feet. No jamming near the cell tower. 85 feet from the cell tower the jamming started and continued for about 50 feet.

I THOUGHT an engineer's forum would be a good place to ask what could cause it.(jamming of certain radio freqs) I don't know if car door openers and garage door openers operate on the same band. But I though someone on here would know. I guessed wrong, didn't I.

I have come to notice that I can post as Guest and get more answers than posting under my name.

Time for me to leave this board, let the "good ol' boys" have it all to themselves.

ADMIN, delete my account. This place isn't friendly to people who don't fit in with "the good ol' boys".

Thank you.

No body is picking on you, your problem is somewhat germane and unusual.

Were you expecting a specific answer so quickly??

Howdy, MrChevy! (assuming that your account still exists in here!)

The bit about insect/rodent repellers, etc. was a genuine answer. Sometimes there are extremely busy signal areas. They occur next to Cellular repeaters, broadcasting towers, signal generators, and high tension lines of either variety. Normal broadcasting signals can become lost or garbled in these areas. Look up and around. Have any new broadcasting or repeater antennae been installed near your garage lately?

Try a triangulation experiment. Draw straight lines from your opener's receiver to the corners of your 'dead' box, and extend them out to see if they encompass a building. Then investigate what there is about that building that might be causing the difficulty.

Mark

Rotag1 is on the right track. The problem is likely due to multipath, that is: the clicker signal being reflected two or more times off of adjacent structures like the cell tower, and arriving at the door opener receiver out of phase cancelling out one another. The mystery parking lot area is just sometimes known as a dead zone.

Sometimes this type of problem can be resolved by moving (reorienting) the receiver antenna (often a short piece of insulated wire).

Yes, but what has changed since the clicker worked correctly? And now is working again, something is changing. Does any one know what frequencies these transmitters use? What other devices use the same, or similar frequencies? Any ideas?

MrChevy: Your Door Opener situation reminds me of my simular case.

I have a 2 car garage with seperate openers( the older one doesn't have the safety beam across the bottom of the doorway, but the newer one does.)

The first problem I discovered, the newer opener unit, the door would be open when I came to the garage. Thinking My Wife or myself, left it open, until I watced it close while a Taxi Cab keyed his microphone to talk, while he is coming around my corner.

Checked with the Supplier of the Door Opener; I was told:" This IS Quite Common, Go home and see if my model has a channel select switch, If it does, switch it, this changes the Channel Frequency." I did this, and we didn't have this problem again,BUT I could now operate my garage door from a further distance up the street.

About 100 feet further than the 150 foot Maximum I could depend on before. The story didn't stop there. The street light on our corner was originally mounted on a wooden pole. The crews came and changed our Street Lights all to the Newer Metal Poles, with Photo cell operated Mercury Vapor Light. Now I have to watch where I operate by Door Opener from. I have walked the sidewalk with the Car Opener in my hand, & if I am positioned so that 30 ft light mast is between me and the Door opener unit in the garage, the door won't open until I am closer to the Garage (the length of my Lot 125 feet, the street lamp is on the Property Line about 15 feet from the corner, in line with the doors of my garage). So now we wait that extra 10 feet, coming around the corner, before we push the door opener. Your Interested Friend, Retired TroubleShooter, Carl.

Hi Guys,

RF is indeed a little "Black Magic" especial for those not intimently involved in the state of the art. You already have some very good comments as to why this ocured.

Here is a though.. If it should happen again, have a new battery for your clickers handy. Distance, reflections, and all the other afore mentioned things could be the problem, but if your clickers have low batteries that might just the thing that caused the problem. Also, if the batteries were low and you keep using the clickers the batteries will get yet weaker and the problem exagerated. Giving the batteries a rest overnight will let them recover a bit and low and behold the next day the problem is gone. It may come back again soon. Just give new batteries a try. Its cheap and may just eliminate the issue. You don't want to make a carrier of this.

The current generation of garage door transmitters are in the 300-400 MHz range. The latest technology allows the transmitter and receiver to randomly reset the frequencies that will be used in the future every time the transmitter correctly matches the receiver frequency and causes the door to move ( either open or close) this prevents anyone from observing your frequency when you transmit, and coming back later and transmitting on that frequency to gain access to tour building. The better ones choose a string of future frequencies, in case you hit the button before you are within range. if not for that feature, your remote would now have the wrong frequency to open the door. To combat this the systems will go through a select list of frequencies till it hits the correct one that the receiver is expecting.

If the battery is removed from the transmitter, a capacitor is used to remember the frequency that it is supposed to use next. If the battery is out too long, the cap can loose the frequency, and then it will have to go through a search to relearn what it is expected to already know.

The garage door opener people were a little reluctant to give out the information on how the receiver and transmitter are able to recognize each other once the frequencies are not in sync. If something was near operating in the 300-400 MHz range, your receiver might have interpreted that signal as an event, and then needed to re sync to be able to match up again.

I don't know why your transmitter did not work your door. but there are many possibilities that could cause it. But if it does not reoccur, it will be hard to diagnose.

If I were a determined crook, I might want to create a radio broadcaster that would transmit across the 30-400 MHz frequencies. A 25 or 50 watt transmitter would probably open a lot of doors. If this is your business, you might want to think about a better security for yourself.

There are a large number of low power RF devices in use today, I don't know the legal frequencies in the USA, but it may not be relevant as many illegal devices are in use. Radio controlled toys, security systems, walkie-talkies, cameras etc. somebody may have been using one in your area. 300-400MHz sounds as if it may be in the "white space" between analogue TV channels. Somebody may have been testing a new system in your area or a TV crew may have been doing a remote and temporarily using that frequency or one that could cause inter-modulation problems on yours. The possibilities are numerous. Localised RF problems often exist due to reflections from buildings so I would suspect a combination of a temporary transmission combined with reflections from the buildings and terrain to cause the problem.

My son has come across a similar problem a couple of times in his job of roadside repair & recovery, he is convinced that this was caused by the presence of a police CCTV van. He was able to fix the problem by towing the vehicles a couple of hundred yards away from the police van.

This would tie in with previous suggestions about interfering signals assuming that the CCTV was being transmitted.

Getting back to the OP. What kind of power does it take to block a keyfob transmitter from reaching the receiver if the receiver in the vehicle is only inches from the keyfob transmitter?

That has me curious. Everybody is talking about the garage door opener (which is at his shop, not a garage). And yes, everything working fine the next morning. So, forgetting the garage door opener for a bit, what about the vehicles?

Most poster's on here must own a car/pickup that has a keyfob door opener. Sitting inside your car/pickup, you are within inches of the door opener receiver. How much interference does it take to block the receiver from receiving the transmitters signal when they are only inches apart?

As the OP said, move the vehicles just a foot and their keyfobs worked fine, moved them back and nothing worked again.

Hi, Guest (and also Qcddoc2012)

The direct answer to your question,

"What kind of power does it take to block a key fob transmitter from reaching the receiver if the receiver in the vehicle is only inches from the key fob transmitter?"

is

"either a signal that is

• already occupying the receiver's expected reception pattern to the exclusion of any new incoming signal (possibly as interference), that must be
• located either directly at the point of non-communication or
• passing through it in a direct line to the receiver location;

or

• a similarly occupied/located signal source that is activated by the sending device
• when used in the described location."

Or, something that must be explained by esoteric physics, which I find distasteful, or at least frustrating, to counter.

Mark

Thank you Qcddoc2012. It is VERY refreshing to see someone reply who grasps what was asked by the OP.

Question: What kind of money (a guess) minimum would it take to purchase/make something to accomplish that blockage within a 75 foot circle?

I read a small amount about many things and am curious: Listening through the grape vine or otherwise, a guess on how many of these attacks (because I know that is what they are, seems others on here have a hard time grasping that fact) are taking place now in the USA if the answer you can give is not restricted.

And it IS getting worse everyday, whether anyone on this website wants to believe it or not.

Thank you again for such clear answers. There are so many on here in the different threads who can't seem to grasp what is being asked by the OP (original poster) so many times. They take a guess at what the OP meant and then post their dumba$$ answers. I guess life is just a nonlethal game to them and no one gets hurt. And the people who put themselves in harms way, and those like you, protect their "right" to be that foolish.

Hi, Qcddoc2012!

My goodness, what a tirade in response to a postulation that you ended up agreeing with anyway (see notes below)... which kind of makes your opening statement "You have no idea what you are talking about concerning the physics, mathematics or the electronics of jamming technology." open to question as to its motives.

I have promised in the past after doing so to not again go full-bore in a devastating response to opening lines such as this, because I was made to realize by our CR4 fellows that a correction can be made gently, even in the case where it is I who feel slighted by the remark. So I will just make the following observation: We don't generally use that kind of language in here with our fellow engineers, preferring instead to disagree with alternate proofs or even to just agree to disagree in good humour. There's no profit in it, and it's (at least potentially) erroneous mind-reading to belittle the observations you might read in here in that way. You are well educated and without a shadow of a doubt a definite asset in these discussions; but in this instance at least, you might even agree that a well-versed ham radio operator can offer the somewhat less-than-PhD-but-still-cogent observations needed in the discussion in order to sensibly arrive at good conjectures for the anomaly. The various others' slants on the possibilities makes for even better enjoyment in the discussion, and in strange ways sometimes clicks in the mind of a participant in a way that presents a valid solution. I offer that we can enjoy this discussion together on that level and wish to do so with you.

And in that vein, with regard to the remainder of your response:

You seemed to agree with my exact premise that local and focused interference can do the job when you wrote, "Unless their is some jackoff with a parabolic dish sending out a CW white noise signal at a minimum of 10W within 200 meters of the RF dead zone area just as a joke, then there is no explanation for this type of RF blackout" !

I haven't taken your credentials for granted, (or for anything else, for that matter ). And I appreciate that you have some really interesting input as well as valid ideas on the topic.

I would also again like to point out: from your own description, "I have speculated about and proposed theories to account for the phenomenon", that you have corrected my final point about "something that must be explained by esoteric physics, which I find distasteful, or at least frustrating, to counter." by at least indicating that your theories may not totally reside in the realm of esoterica. If I offended you by that statement, I apologize. It was not my intent to do so, but except for the more matter-of-fact magneticism observations he made, poor old Tesla is currently out of empirical flavour with me (although I am in as much awe as anyone else of the Tesla of story and glory); so I have a modicum of skepticism when his name gets used in reference.

Mark

I can't believe you called 911 over a key fob working intermittently.

Maybe he should have checked the batteries first. Mr. Chevy.... your "clicker" is a F.O.R.D.

Radio interference.

key fobs work on the 433 mhz band and this frequencie in th uk was used by the police.

try moving the vehicle a short distance.