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Author Topic: directional garage door antenna ideas  (Read 7584 times)
KB0TKZ
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Posts: 5




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« on: June 27, 2011, 02:52:05 PM »

I am looking to build a directional antenna for my garage door opener, or at least an antenna with some gain.

My receiver is a little box shown here: http://www.hardwareworld.com/Garage-Door-Remote-Control-Conversion-Kit-pGJXIQU.aspx

There is a wire antenna coming out of it thats about 8 inches long. I believe the frequency is around 390Mhz. I was thinking of making a simple 2 element yagi, but where would I connect the "ground" side? I can open the receiver and replace the wire with some coax, but I don't know what I would hook the ground side to.  The receiver itself does not have a ground pin on its 120v plug so I couldn't just connect it to that.

If this is a no-go since I don't have a ground, is there something else I could do to get some gain? Another idea would be to replacethe wire antenna with some coax (but I wouldn't hook up the ground I guess) and run that about 10 feet to a wire vertical at the front of the garage. But I'm not sure if this would be any better since the coax would not be grounded.
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WB2WIK
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« Reply #1 on: June 27, 2011, 03:35:17 PM »

There is almost guaranteed to be an "RF ground" (it doesn't have to be connected to the AC utility ground, or earth ground, anywhere at all -- and on 390 MHz it absolutely wouldn't matter) on the printed circuit board for the garage door opener receiver.  The ground point will usually be a large "plane" of copper either on the back side of the board, or possibly on the components side, or even both.  RF doesn't work without two connections -- trust me, there's a "ground" in there (on the board) and it doesn't matter that it's not connected to any other ground.  It's an "RF ground" for receiver components, including the antenna matching network, that works at 390 MHz.

As such, of course you can disconnect the little wire and add some thin coax (RG58C/U maybe), if you connect to the right two places (where the wire antenna went, plus ground on the board).

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KA4POL
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« Reply #2 on: June 27, 2011, 10:15:39 PM »

There are some unknowns in your posting. You did not mention the material your garage is made of. Most likely wood? Metal would be bad. You also did not mentioned the reason for the improved gain. Usually it should be sufficient to open the garage door just before you reach the driveway. May be you can improve reception already by moving the wire around. Any antenna gain in one direction means a loss in an other. Modern cars have a lot of metal in the windshield. Positioning the transmitter differently inside the car could also help.
And stay away from the primary 120V by any means.
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WB6BYU
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« Reply #3 on: June 28, 2011, 09:11:46 AM »

I'd just put a piece of sheet metal behind the antenna as a reflector.  Something like 24" square might
be a reasonable minimum size, and 36" square probably would be a bit better.  Just put it 5" - 6" behind
the existing antenna antenna from your preferred direction.  If you want more gain you can try a
corner reflector with two sheets, or bend one into a parabolic shape, the flat sheet is the simplest
and the dimensions are not critical with respect to frequency.
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W3LK
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« Reply #4 on: June 28, 2011, 03:23:02 PM »

I'm curious as to the need for a gain antenna. What kind of range are you needing?

My current residential unit has a range exceeding 250 feet and the one in my office building in Baltimore had a range of well over 400 feet.
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K7RBW
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« Reply #5 on: June 29, 2011, 06:50:03 AM »

I was having problems with my garage door opener's range and suspected interference. The frequency was 300.0 MHz (as reported and measured by a freq. counter), which I believe is a standard (to the extent these things are standardized).

I put ferrites around the wires going into the opener: the sensor leads and the power cable and then just added another 4 feet of wire to the 8" that was dangling out of the bottom.

Not particularly scientific, but that seemed to help improve the range enough. There are still times when it only works with the remote about 10' away, but they're just infrequent enough not to bother with now.
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W3LK
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« Reply #6 on: June 29, 2011, 07:58:48 AM »

How old is your system? Is it digitally encoded, and if so, have you checked that the encoding DIP switches on both the transmitter(s) and the receiver match?

Range should not vary that much.
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AA4PB
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« Reply #7 on: June 29, 2011, 08:21:21 AM »

This may be of interest:

http://www.garage-doors-and-parts.com/remote-interference.html

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W3LK
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« Reply #8 on: June 29, 2011, 01:31:06 PM »

One other thought ...

You do have a fresh battery in the transmitter(s) ...

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K1CJS
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« Reply #9 on: June 30, 2011, 08:07:39 AM »

You may find that if you improve the gain too much, you'll have your garage door opening unexpectedly whether you are home--or not.  If the door does open when you're in the driveway, I wouldn't try improving the antenna system too much.  You may get unexpected results.
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W0BTU
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« Reply #10 on: July 01, 2011, 05:09:50 PM »

You may find that if you improve the gain too much, you'll have your garage door opening unexpectedly whether you are home--or not.  If the door does open when you're in the driveway, I wouldn't try improving the antenna system too much.  You may get unexpected results.

That's exactly what I was thinking.

I once had a garage door opener with a RX gain adjustment, and if I set it to max, I would come home and occasionally find the door had opened by itself.

There's lots of RFI in this world: power line noise, neighbor's plasma TV's, computers, to name just a few. Given enough time, some RFI source will emit the code sequence needed to operate the door, if the opener has too much sensitivity.

Why do you think you need a directional antenna?
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KA4POL
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« Reply #11 on: July 01, 2011, 10:06:47 PM »

We have now quite a few proposals and questions. I think it's time we hear some comments from KB0TKZ. Or should his problem already be solved?
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K1CJS
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« Reply #12 on: July 03, 2011, 07:30:24 AM »

After a little thought, this occured to me.  You just may have a TRANSMITTER that needs repair.  Not only would a weak battery cause reduced range, but damage to the remote would also.  If the remote had been dropped, a circuit board may have been damaged enough to reduce the signal out.  If possible, check this out, and make repairs if needed and if you are able to.  That may solve your problem.  Good luck!
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N6AJR
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« Reply #13 on: July 08, 2011, 04:27:46 PM »

I used to have  end of the block range, with a wooden slab type door.  then we went to a nice metal, roll up door, and now the  thing is lucky to open from the drive way.  I keep meaning to either extend the wire, ot staple it up so it is above the door,  or both.  the metal door definately cuts down on range. same opener and  remotes, only changed the door.
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