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Thread: Any amateur radio gurus out there?

  1. #1
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    Any amateur radio gurus out there?

    we are experiencing interference on our garage remotes. We have two garage door openers running at 315mhz. Other than power, these are two separate systems and both have deteriorated simultaneously. At the same time, our neighbor reports that the key fob on his suv is no longer working when at his house. The car is fine anywhere else.

    our garage has an aluminum door and siding. Before I heard from the neighbor, I bought an antenna kit from lift master and moved one antenna to the outside of the building. I should not that the antenna is screwed to and os parallel to the metal siding. That helped some. We can now open the door if the car is within 20 feet.

    my thought is that someone has installed something around here that’s causing problems. What I’m doing here will help but the real solution is to find the culprit.

    I was looking into an rtl-Sdr that can hook up to my android phone and maybe go on a fox hunt. But I would need some advice. I’m looking at rtf-SDR.com where the offer a radio dongle and then I thought I would build my own cheap directional antenna.

    so, anyone have suggestions?

  2. #2
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    No expert by any stretch, but in my previous life (house), my neighbors had similar opener issues. I followed developments only casually, as I was in the middle and had no issues at all.

    They were convinced it was a small AM radio tower situated nearby. Apparently it was sold and the new (foreign) owners decided that power restrictions were merely suggestions. One neighbor even reported hearing the station's programming 'playing' in the garage, even tho' there was no receiver there? FCC and the city got involved, but I moved and not sure of the final outcome.

    I think you're on the right track ... looking at interference from new transmitters.
    Molann an obair an saor.

    If Heaven ain't alot like Texas, I don't wanna go. - Hank Jr.

  3. #3
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    Have any new antenna towers gone up in your area?

    Any old ones that may have been returned to service?

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  4. #4
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    I no expert either, but before I retired I was tasked to correct the same problem for a customer. The boss said heres a interference finder seemed to be a broad band r.f. receiver with a meter. Turned out a new hospital was built near the customer and the meter peaked near there. I thought it my have been data transmission from the hospital. They had several antennas on the roof. Like you I added an external antenna that was only slight improvement.
    Bill

    " You are a square peg in a square hole, and we need to twist you to make you fit. " My boss

  5. #5
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    I plan to ask around to see if more neighbors are having problems. Interestingly, most folks around here (Dc area) dont use their garages for cars. Im told that its an east coast vs midwesterners thing. Midwestern people park their cars in thagarage. East coasters use the garage for junk and the car lives outside. It pretty much holds true for my neighborhood. I dont know about the wider area. Anyway, many of my neighbors wouldnt use their garage doors much.

    i dont know much about 315 MHz. I know that garage remotes use it as do many car remotes. Does anyone know where I might find a list of devices that might be culprits?

  6. #6
    If you google "neighborhood garage door openers not working", you'll see you're far from the first people to have this problem...

    This is, perhaps, my favorite cause: https://bgr.com/2019/05/06/science-n...-door-openers/

  7. #7
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    also, crappy led light bulbs in garage door openers can stop them from working.

  8. #8
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    Roger, just recently, maybe 5-6 month ago I read article in local newspaper about same problem in one of the NOVA county. Culprit was military installation in the area which kills all remotes for garages. If I remember correctly, nobody took responsibility.(

    I am in your area.
    Ed.

  9. #9
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    A resource on rfi

    http://www.arrl.org/radio-frequency-interference-rfi

    It can be a bit more complicated than just looking for 315 MHz
    It can be that the sum or difference of two signals comes out at 315. The receivers on garage doors and vehicles can be desensed by strong signals.

    John N5PEE
    Last edited by John Stankus; 01-02-2020 at 10:01 PM. Reason: Spellchecker doesn’t like desensed

  10. #10
    ^^^ concur with this --

    Not sure of proper terminologies, but 'harmonic' radio waves, which I understand to be simply, frequencies divisible by or in multiples of X frequency can interfere with that frequency.

    As to what can be done about it, probably nothing, since the FCC's catch-22 rule is useless: your device can't interfere with other devices, but too bad if other devices interfere with YOURS.

    My opinion: cell phone towers, bluetooth and LED bulbs can't be helping...
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  11. #11
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    Lift master offers a universal receiver with security+ 2.0. They claim that it transmits on three frequencies and virtually eliminates interference. It appears to use 310,315 and 390mhz. Ive tried to hunt up what this miracle is but cant find much other than advertising claims. Anybody know more?

    heres a link http://www.gateopenersunlimited.com/...s%20Poster.pdf
    The receiver is the 850LM. Says it can control three doors or gates so I would only need one receiver for my two doors.

    i could abandon my current receivers and use this thing. That may be the next step if moving the antennas doesnt help.

  12. #12
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    There also possibilities of where the interference is getting into the receiver. If it’s traveling through the power lines or lines to sensors a ferrite choke might help .
    https://palomar-engineers.com/bullet...-Kit-p74369055
    https://www.k6jrf.com/FT2k_GDO_Fix.html

    John

  13. #13
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    Quote Originally Posted by John Stankus View Post
    There also possibilities of where the interference is getting into the receiver. If it’s traveling through the power lines or lines to sensors a ferrite choke might help .
    https://palomar-engineers.com/bullet...-Kit-p74369055
    https://www.k6jrf.com/FT2k_GDO_Fix.html

    John
    Ordered two kits. Moving the antenna outside has helped but not a lot. I realized that the two openers do share a common ac power supply. This should eliminate the ac circuit as a source. I have my doubts though. There’s still my neighbor reporting that his car fob doesn’t work when the car is in his driveway but does work everyplace else.

  14. #14
    I was involved in ham radio as a teenager back in the 60's, and learned a bit about harmonics from citations from the FCC.

    In your situation, it must be a continuous source, as any communications radios would be used intermittently. I looked at several sites on the web but saw nothing specific around the 315 mhz. It could be some sort of data transmission on a nearby frequency that is spilling over, "slop and splatter" were the terms we used back in those dark ages.

    Here's a list of some possible sources:

    • Nearby airports
    • Television or radio transmission towers
    • Military installations and ships cruising up and down the sound and ship canal
    • Power lines
    • Cell phone towers
    • Appliances within 10 to 15 feet of the receiver whether they are running or not.
    • 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, especially LED (Light Emitting Diode)
    • Any number of small appliances. One of the most common culprits is cheap clock radios.
    • Air conditioning or heating system thermostats
    • Florescent lighting fixtures
    • Halogen lighting fixtures
    • Ham radio transmitters.
    • Car battery chargers
    • Motor Homes

  15. #15
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    Yikes!! Thats quite a list. The Christmas tree lights are interesting as the symptoms started about when lights started going up. Most are now Dow and its not better.

    The DC area is chock full of military. As posted earlier, a whole town was pretty much shut down by the military so thats always a possibility.

    some things like the RV I can easily throw out.

    Im moving the other antenna outside and putting ferrite chokes on the AC and other wires. Im still trying to find out if another receiver would help.

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