Garage door opener antenna problem.

[markls8]

Is there a way to attach a lead to the in-garage receiver antenna so that it can be moved about 9 feet so as to pass through a brick wall? My range is very poor and the installer says he can't do anything about the poor signal penetration through a brick wall.

I figure I may be able to fashion some kind of lead of calculable impedance which will allow the antenna to hang outside. Otherwise I will have to run some heavy-duty wires to move the entire unit to the outside. I think the system is 40 MHz. It's not the car TX - the system works great on another door I tried it on.

Any suggestions, even for experimenting, would be appreciated. I know I'm not "supposed" to monkey with this, but the setup was somewhat costly and is next to useless (have to be right in front of it) as it is. I'm in a somewhat rural location.
Thanks and best regards - Brian.

 

[VEBill]

I don't that many GD Openers would be 40 MHz. Most are UHF, around 310-390 MHz.

If I were in your shoes, then I'd first double-check the receiver circuit for proper power line isolation (does it use a proper power transformer?). If it isn't isolated with a transformer, then it probably has a safety-rated series capacitor on the antenna wire. All this is just to be very careful if you're planning to interface an external antenna.

Once you're safe, then simply install a BNC connector onto the unit, trim the dangling wire antenna and connect it to the new jack. Then run some coax cable outside to the new antenna. The new antenna might be a simple colinear dipole in a plastic tube.

Be prepared to be disappointed. The world of GD Openers often includes cheap superregenerative receivers and other such nonsense. There's many reasons why something like an external antenna that should help, might not work at all...

Better advice is that you might try looking for an external GD Opener receiver module that can be wired into the external contacts. This would be more of a common, off-the-shelf, solution and would avoid the risk of disappointment.

 

[Comcokid]

Try this simple method: Take a length of coax (50 or 75 Ohm). Strip back the shield at each end several inches leaving only the center conductor (idealy 1/4 wavelength at the operating frequency). Place one stripped end parallel to your garage door opener antenna about an inch away. Run the other end out of your garage.

This method works well when you have a wireless device inside a metal building or other self-shielding building where path loss through the wall is substantial. I don't know if it will really help in your garage situation. It does have the advantage in that the garage opener does not need modification.

 

[markls8]

Thanks for the suggestions. I'll do some simple experimenting once the thermometer rises to more reasonable temperatures.
Curiosity question: could I not measure the antenna length and determine the frequency by calculation, assuming it's 1/4 wave, roughly? It's not listed anywhere in the literature.
Thanks - Brian.

 

[VEBill]

The assumption that the antenna is 1/4 wavelength may not be correct (but who knows?).

If you 'Google' the model number, you're likely to find some information. Often, the makers of aftermarket Remote Controls (for GD Openers) will have tables showing such details as frequency and signal type.

Also, you can check the FCC website for the FCC type approval number. They'll have complete details.

 

[searsjames]

Would it not just make sense to match the existing length of the hanging wire? I.E. Strip the coax back this far at each end.

Dont forget to ground the coax shield to the opener case.

 

[Higgler]

I'd use twin lead cable, the old fashion two wire stuff that antennas roof mounted antennas are sometimes connected to. I think you can still get it at Radio Shack. Connect the two wires, one to the case (find a metal part in case it's plastic) and one to your antenna wire. When you get it outside, separate the two wires by pulling them apart, you can do a distance check and pull them more apart to optimize your range. Also reorient it from horizontal to vertical to optimize your range.
Kevin.

 

[markls8]

searsjames - yes, that makes good sense, but makes the assumption that the antenna was originally made to the correct length, which I don't believe every manufacturer does every time. I think calculating the 1/4 wave length from the freq would be dead-on (when I find it out.) An incorrect antenna length could be a contributing source of my problem.
Higgler - I happen to have a length of flat lead around. So it's easy - I'll try that first.
Thanks all - Brian.

 

[Digitalwoodshop]

I like the Twin Line idea too. Split it and test the result. Get too long clip some off....
A little off topic, something that I witnessed in San Diego in 1989.  The local TV news crew was doing a live newscast in this coastal community that was within sight of the ocean. The live shot was of a long street and at random, garage doors were opening and closing.  All the homes were built by the same builder and all the Garage Door openers were all manufactured by the "Overhead Door Co." of Everett, Washington. The residents called the news crew. In most cases the owners were not home at the time of the random activation.
I am retired Navy Radar Computer Tech FCC(SW), I was on Active Duty at the time. I hit the nail right on the head as to what the problem was as reported days later by the TV News.  
 A group of Navy ships with a Carrier was off the coast getting ready to play war games at Camp Pendelton.  The door openings and closings continued until the ships went over the horizon.  When they returned, so did the random door openings. Navy PR said it was NOT the cause.  I knew a new digital communication system was being tested at that time that operates in the 200+- to 400+- Mhz Military Band. I believe the garage remotes were somewhere around 320 Mhz if I remember right. Throw enough 1's and 0's out there and you never know. I believe the end result was all the garage door openers were replaced with name brand units.
OK... I know what your thinking....  "That sounds like a Navy SEA STORY"  Well... Check out this link...  

http://www.wired.com/news/technology/0,1282,19166,00.html

 I was right on the 320 Mhz too....   And check out this one...  Hawaii and Washington State..  

http://starbulletin.com/98/07/31/news/story10.html

Question? Do you live near a Military Base? Interference from other transmitters could be cutting the receiver sensitivity.

Thanks, Al

 

[photistor]

If you haven't found the frequency yet you may try searching the FCC number (usally printed near the model and serial number) try the following sites:

http://www.fcc.gov/oet/fccid/help.html

https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/GenericSearch.cfm

http://www.driverzone.com/fcc_reg.htm

 

[markls8]

I do live on the north shore of Lake Erie, about 20 miles from a USAF reserve base in Niagara Falls, but visits from the Navy ships on the lake are rare here. Interesting articles though.
False opening/closings are as old as remote GD openers. When I was a wee lad in the '60s their spontaneous actions were somewhat regular (once every year or so) , and for security Dad always unscrewed the fuse whenever we left for vacation. (That receiver had tubes in it and was the size of a large lunch kit.) Although newer technology (rolling codes) makes this less frequent, and more secure, I still like a "vacation" mode on my opener.
Looks like some signal "jamming" was going on as well.
Thanks for the info. - Brian.

 

[Higgler]

One other thought that's used sometimes is to make your walls transparent by adding an antenna on both sides of the wall and connect them with a cable. So if for example your antenna was inside a metalized garage, i.e. total blockage of energy to the outside. You could have a pair of antennas that are on either side of a metal wall and connect them thru the wall with a cable. That would make the wall effectively transparent at that antenna location. For the entire garage to be transparent, you'd have an antenna every 1/2 wavelength. Though that would be ridiculous in this case. A very similar thing is done on some high speed missile radomes. You can make this pointy radome out of metal and print antennas on both the outside and inside surfaces, then connect them together with a single wire and the metal radome effectively disappears, similar to your garage walls disappearing. There are similar commercial products that allow you to receive GPS inside a building, they add an amplifier between the antennas too.
Kevin.

 

[VEBill]

"...make your walls transparent by adding an antenna on both sides of the wall and connect them with a cable."

In the general case, the word "transparent" would very much overstate the possible improvement of such a passive rebroadcasting system. Compare the total loss of such a system to the pathloss of another 30cm of air...

The amplifier used in the GPS kit is a critical element to make such a system actually work.

Of course, if you have virtually ZERO signal behind a concrete wall, then any amount at all is infinitely better...