Connect with us

Military radio signal jams garage doors

Discussion in 'Electronic Design' started by Igor The Terrible, Dec 3, 2006.

Scroll to continue with content
  1. OK...here is an example of what NOT to do when testing RF equipment.
    So if you were one of the unfortunate souls that had to open your
    garage door manually, be happy it wasn't in the middle of a hail
    storm!!



    Military radio signal jams garage doors By ROBERT WELLER, Associated
    Press Writer
    Sat Dec 2, 5:03 PM ET


    DENVER - What do remote-control garage door openers have to do with
    national security? A secretive Air Force facility in Colorado Springs
    tested a radio frequency this past week that it would use to
    communicate with first responders in the event of a homeland security
    threat. But the frequency also controls an estimated 50 million garage
    door openers, and hundreds of residents in the area found that theirs
    had suddenly stopped working.


    "It would have been nice not to have to get out of the car and open the
    door manually," said Dewey Rinehard, pointing out that the outage
    happened during the first cold snap of the year, with lows in the
    teens.

    Capt. Tracy Giles of the 21st Space Wing said Air Force officials were
    trying to figure out how to resolve the problem of their signal
    overpowering garage door remotes.

    "They have turned it off to be good neighbors," he said.

    The signals were coming from Cheyenne Mountain Air Station, home to the
    North American Aerospace Defense Command, a joint U.S. and Canadian
    operation set up during the Cold War to monitor Soviet missile and
    bomber threats.

    Technically, the Air Force has the right to the frequency, which it
    began using nearly three years ago at some bases. Signals have
    previously interfered with garage doors near bases in Florida, Maryland
    and Pennsylvania.

    In general, effects from the transmissions would be felt only within 10
    miles, but the Colorado Springs signal is beamed from atop 6,184-foot
    Cheyenne Mountain, which likely extends the range.

    Holly Strack, who lives near the entrance to the facility, said friends
    in the neighborhood all had the same problem.

    "I never thought my garage door was a threat to national security," she
    said.

    David McGuire, whose Overhead Door Co. received more than 400 calls for
    help, said the Air Force may be able to slightly adjust the
    transmission frequency to solve the problem. If not, it will cost
    homeowners about $250 to have new units installed.

    "The military has the right to use that frequency. It is a sign of the
    times," he said.
     
  2. Guest

    | OK...here is an example of what NOT to do when testing RF equipment.
    | So if you were one of the unfortunate souls that had to open your
    | garage door manually, be happy it wasn't in the middle of a hail
    | storm!!

    Why not?

    I presume this is all operating as a secondary unlicensed spectrum
    user. The garage door company perhaps should have used some other
    frequency in the first place.

    But I also worry about the fact that this was a small area. While it
    may well jam the door radios nearby, would this signal make it to the
    intended first responders all over the country?

    I'm curious about the frequencies involved. Possibly it's not dead on
    the same one, maybe off by 1/2 MHz, and just overloading receivers as
    opposed to blocking the signal of the tiny transmitters. Adjusting
    the frequency a little wouldn't do any good.
     
  3. Jim Thompson

    Jim Thompson Guest

    Clear back in 1950, 390MHz was assigned to the military. But _some_
    garage-door-opener companies have continued to use that frequency
    based on the FCC "low-power-non-interference" rule.

    In COS the openers were simply over-powered by a high power military
    antenna located on Cheyenne Mountain.

    BTW, Cheyenne Mountain Resort Hotel is a great place to stay while
    consulting in COS ;-)

    ...Jim Thompson
     
  4. legg

    legg Guest

    Unfortunately, the US military uses it's equipment in other places, it
    seems, without bothering about homologations.

    http://www.cbc.ca/canada/story/2005/11/04/ottawa-signals051104.html

    The FCC is, after all, only a USian agency.

    RL
     
  5. Guest

    This story is from Denver, Colorado but is applicable to Alaska since
    we have so many military installations, the new missile defense project

    at Ft. Greely not being the least. The ionospheric heaters located
    near Glenn Allan and the BMEWS radar located at Clear both have caused
    massive radio frequency interferences in the past. Just ask any pilot
    that has flown into the radar signal or long time residents of Glenn
    Allan. I live between Ft. Wainwright and Eielson AFB and often
    experience strange signals on my cell phone and through my upstairs TV.

    During my time in the US Army I worked at a frequency monitoring
    station at Ft. Huachuca, Arizona where we attempted to find
    interference among the many military signals that operated during war
    time exercises. It was a futile attempt to say the least. Radio
    signal interference from the military's many transmissions can come
    from harmonic signals generated by two or more signals. These harmonic

    signals are difficult to detect and correct.

    What is not known is the long term health risks associated with the
    barrage of radio frequency signals that penetrate our body every day.
    Millions of these transmissions come from earth and satellite
    transmitters and grow in number. No one knows what the end result will

    be.
     

  6. I haven't seen Ft. Greely since I left the US Army in 1974. Are you
    working on the project, or just living near the old base?

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     

  7. Aren't those band segments reserved for military use worldwide by
    international agreement?


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  8. zeez

    zeez Guest

    Hmm, I remember hearing of an incident of Sputnik screwing with garage
    door openers back in the day. :)
     
  9. Jim Thompson

    Jim Thompson Guest

    I was a Senior in High School when Sputnik went up. I don't think RF
    garage door openers existed back then ;-)

    ...Jim Thompson
     
  10. Guest

    |
    |>
    |>Jim Thompson wrote:
    |>> On 3 Dec 2006 16:07:56 GMT, wrote:
    |>
    |>> Clear back in 1950, 390MHz was assigned to the military. But _some_
    |>> garage-door-opener companies have continued to use that frequency
    |>> based on the FCC "low-power-non-interference" rule.
    |>>
    |>> In COS the openers were simply over-powered by a high power military
    |>> antenna located on Cheyenne Mountain.
    |>>
    |> Hmm, I remember hearing of an incident of Sputnik screwing with garage
    |>door openers back in the day. :)
    |
    | I was a Senior in High School when Sputnik went up. I don't think RF
    | garage door openers existed back then ;-)

    If not then, soon after. My grandfather's brother had a remote garage door
    opener in 1961. I can't say whether it was optical or radio as I was a bit
    too young then to consider it important. But I sure thought it was great.
    It might have been rather expensive at the time.
     
  11. John  Larkin

    John Larkin Guest

    Garage-door openers are some of the worst RF gear around. Receiver
    selectivity and overload tolerance is crap. If they want to operate
    near military bands with garbage receivers, they shouldn't complain
    about being blanked.

    John
     
  12. hob

    hob Guest

    I am curious as to if/how they are jamming those encoded "digital" signals
    that garage door openers have used for the past 15 years.

    1) If the military signals are interfering with those digital commands, then
    the signal must be overwhelming the receivers - they surely are not sending
    simultaneous multiple sets of "trains" of pulses that fool all those
    receivers' security, weak as it is.

    2) If they are overwhelming the digital receivers instead of "stealing the
    codes" so as to make them not work, they must be pumping out one hell of a
    lot of power, relatively speaking - and that means the residents are being
    subjected to the same steady barrage of RF.
    And from days past, memory had the 390M range as not being particularly
    friendly to humans (you don't feel anything until after any damage is done)

    3) And curiously - if it jams the local garage door openers so well, why
    isn't the miltiary using them in Iraq to jam the IED
    detonators? -(apparently GDO remotes are the new favorite detonator of the
    anti-US forces in Iraq)

    from a former eccm tech...


    |------------------------------------/-------------------------------------|
     
  13. Garage door opener remotes don't have a lot of power. It won't take THAT
    strong of a signal to swamp it out and overload the receiver. It's a S/N
    issue.
     
  14. Guest

    | I am curious as to if/how they are jamming those encoded "digital" signals
    | that garage door openers have used for the past 15 years.
    |
    | 1) If the military signals are interfering with those digital commands, then
    | the signal must be overwhelming the receivers - they surely are not sending
    | simultaneous multiple sets of "trains" of pulses that fool all those
    | receivers' security, weak as it is.

    I'd guess it most likely is an overload of cheap receivers.


    | 2) If they are overwhelming the digital receivers instead of "stealing the
    | codes" so as to make them not work, they must be pumping out one hell of a
    | lot of power, relatively speaking - and that means the residents are being
    | subjected to the same steady barrage of RF.
    | And from days past, memory had the 390M range as not being particularly
    | friendly to humans (you don't feel anything until after any damage is done)
    |
    | 3) And curiously - if it jams the local garage door openers so well, why
    | isn't the miltiary using them in Iraq to jam the IED
    | detonators? -(apparently GDO remotes are the new favorite detonator of the
    | anti-US forces in Iraq)

    Good question. It might need to be on a very close frequency for the
    overload to be effective by getting through the first stage filter.
    Maybe the IEDs get set up with a variety of unanticipated frequencies.
    It might be needed to be within less than 1% of frequency to be able
    to do an effective overload.

    A base station probably could not do this overload for other than its
    immediate area. That would mean putting the transmitters on the field
    vehicles. But as soon as they do that, expect some RDF missles to
    start showing up in the hands of insurgents, if they figure it out.

    BTW, I've actually overloaded a couple GFCI receptacles with my 2 meter
    hand held ham radio transmitter running at 5 watts to a rubber duck
    antenna at a distance of 10 feet. Those things really freak out when
    that happens. It could have been a resonance in the wiring.
     
  15. zeez

    zeez Guest


    And probaly without the modern coding remotes have today. (remember,
    computer took up
    entire rooms at this time. :) I wonder if the first RF garage door
    openers listened for a specific audio tone broadcasted by the radio
    transmitter, or simply responded whenever
    an RF signal was detected on its frequency.
     
  16. zeez

    zeez Guest

    When I was young, I hooked up a 5 wattt mobile CB directly to the
    antenna inputs of a
    portable B&W TV. Ended up frying the sucker (the TV, not the radio. :)
     
  17. zeez

    zeez Guest

    I wonder if they sell garage door openers and remotes that use
    challenge-response. It wouldn't be that expensivge to do.
     
  18. zeez

    zeez Guest

    I wonder if they sell garage door openers and remotes that use
    challenge-response. It wouldn't be that expensive to do.
     
  19. Jim Thompson

    Jim Thompson Guest

    I have problems with steel doors, and walls that use metal mesh for
    the stucco, so my range is crap.

    I'v been considering some kind of IR replacement. Any available
    commercially?

    ...Jim Thompson
     
  20. Guest

    |
    | wrote:
    |> |
    |> |>
    |> |>Jim Thompson wrote:
    |> |>> On 3 Dec 2006 16:07:56 GMT, wrote:
    |> |>
    |> |>> Clear back in 1950, 390MHz was assigned to the military. But _some_
    |> |>> garage-door-opener companies have continued to use that frequency
    |> |>> based on the FCC "low-power-non-interference" rule.
    |> |>>
    |> |>> In COS the openers were simply over-powered by a high power military
    |> |>> antenna located on Cheyenne Mountain.
    |> |>>
    |> |> Hmm, I remember hearing of an incident of Sputnik screwing with garage
    |> |>door openers back in the day. :)
    |> |
    |> | I was a Senior in High School when Sputnik went up. I don't think RF
    |> | garage door openers existed back then ;-)
    |>
    |> If not then, soon after. My grandfather's brother had a remote garage door
    |> opener in 1961. I can't say whether it was optical or radio as I was a bit
    |> too young then to consider it important. But I sure thought it was great.
    |> It might have been rather expensive at the time.
    |
    |
    | And probaly without the modern coding remotes have today. (remember,
    | computer took up
    | entire rooms at this time. :) I wonder if the first RF garage door
    | openers listened for a specific audio tone broadcasted by the radio
    | transmitter, or simply responded whenever
    | an RF signal was detected on its frequency.

    My guess would be an audio tone. A more advanced design would compare
    to a 2nd audio tone such that the 1st must be stronger. They did have
    a means to reject neighbors. I remember my uncle mentioning his neighbor
    (in an area of expensive homes) also having one of these and they did not
    operate each other. Being RF frequency selective would be a bit hard to
    do for such cheap electronics. I have no idea if the audio would have
    been AM or FM modulated, but my guess would be AM. Still, it could easily
    be FM with the 2 tone test where one has to be much higher than the other
    to reject all the background hiss from FM demodulation.

    These days, I'd want to make one with a challenge response security system
    built in so "the code" itself is never actually sent. For example, the
    remote makes a request to the base, the base generates a random number,
    encrypts it, sends one or the other to the remote, the remote does the
    same if sent the number or decrypts if sent the result, and sends back its
    result for confirmation and action. As long as it's very hard to derive
    the key from those two pieces of data, it should be reasonably secure.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-