The in basket: Ellen Schroeder , who lives on Bremerton’s east side, wondered what I knew about the problem she and her neighbors have when some operation inside Naval Base Bremerton immobilizes their garage doors.
Actually, it’s the remote controls that stop working. The doors still can be operated manually or with the inside button. But at intervals, the remotes won’t open or close the doors. That’s quite a hassle for the mobility impaired or just about anyone on a windy, rainy day.
“Today it wasn’t a problem,” she told me on Oct. 26, “Last week it was intermittent, but happened almost every day.”
The out basket: Ellen said she had gotten her garage door from Kitsap Garage Doors and Chelsea Browning, the office manager there, says the industry is only too aware of the problem. It also sometimes affects keyless entry devices on cars, she said.
She referred me to the Web, where Googling some combination of “garage door openers,” “military bases” and “interference” brought up a number of discussions of this issue.
Chelsea says it’s all part of stepped up security that followed the attack on the Twin Towers in New York. As such, her company and the rest of the industry haven’t been able to learn what exactly causes it. The Web sites name something called the Land-Mobile-Radio System as the origin of the interference.
Tom Danaher, spokesman for the Navy here, referred me to a telecast discussion of the problem on NBC, which he said covers it.
“(Department of Defense) is the authorized user of the 380 MHz to 399.9 MHz spectrum, (and) it is under no obligation, according to the FCC, to identify or mitigate potential interference (with) devices that may also be operating in that spectrum,” it said.
It then drew from a recommendation from the garage door industry, found online at http://www.dasma.com/PDF/Publications/TechDataSheets/OperatorElectronics/TDS374.pdf.
It said, in part, “If a military radio system (which usually consists of high-power devices) causes your … device to malfunction, then, by law, you must accept the interference.”
A homeowner with the problem should
call the manufacturer or retailer of the garage door opener, it said. “Buying a new garage door opener is probably not necessary. But you may need to purchase a retrofit to your remote control system to allow operation on a frequency that is not used by your local military.”
Easier said than done, says Chelsea at Kitsap Garage Door. The industry advised shifting from a remote using the 390 MHz frequency to one on 315 MHz, but that doesn’t work here, she said.
Going up to a frequency in the 400 MHz range will work, she said, but fewer than half the existing remotes are compatible with that range.
Ellen didn’t think I’d be able to do anything but explain the problem, which is a good guess. In fact, I won’t even try to explain it beyond what I’ve already written. Discussions by people who know electronics far better than I can be found on the Web, and I commend anyone interested to use those sites.
