On Mon, 23 Jul 2012 09:43:10 -0700, "Wayne"
wrote:

Military ELMR equipment is authorized for 380-399.9 MHz.
Garage door openers that operate low power unauthorized in the same band are
sometimes messed up.

Wonder if the military or the garage door opener company will win...

http://www.theday.com/article/201207...307239975/1018

It's not exactly ELMR but rather LMRS (Land Mobile Radio System) at
380-400MHz interfering with garage door openers on 315 MHz through
receiver blocking (overload):
http://en.wikipedia.org/wiki/Land_Mobile_Radio_System
This has been a known problem for at least 8 years, yet the garage
door manufactories haven't done anything in the way of improved
receivers. I guess a cheap bandpass filter and some shielding would
be too much for the cost concious garage door opener manufacturers.

Drivel: One of my customers was having problems with their garage
door opener. They said they could easily close the door from the end
of the driveway, but could not open it again from the same location.
When I arrived, I found that they had an aluminum garage door, with
the receiver mounted behind the door. Between the metal door and
aluminium foil backed insulation in the walls and roof, the garage
made an effective screen room. I moved the recevier and wire antenna
to a better location, which fixed the problem.

More drivel: Many years ago, I helped setup a 30 watt Mitrek 440MHz
portable repeater for an event. Since it used mechanical T/R relays,
the dropout time was set rather long to minimize contact cycling.
During the event, we had some traffic from drivers in the nearby
parking lot about being unable to operate wireless car alarms. Oops.
I turned down the TX power which allowed the alarms to operate
normally. Years, they switched to VHF, which stopped blocking the car
alarm receivers, and introduced triggering the car alarms.
Lesson learned: Use low tx power in parking lots.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558