We appear to have a black spot round our front door. I've managed to set off the car alarm twice now, just using the remote to open the doors. And half the time, the remote doesn't seem to want to work, while it does work perfectly well elsewhere. Also, we have a weather station, with a remote sensor just under the porch, and it seems to be attempting to transmit all the time, and the battery is draining fast, and its readings are totally laughable (from -20 to +20 C in a mere thirty seconds, while at a constant 20% humidity? I think not).
I just checked.
It appears that car remotes work on 433 MHz, just as the weather station does, and it looks like we've got a nice little punch-up going over who owns that frequency in that ten foot diameter area. I think we may have to find somewhere else to mount the sensor.