I experience the same symptom: the door lock remote decreases in range from 15 meters to 1 meter. My car is a Citroen CX with an aftermarket (which does *not* mean cheap and crappy here!) remote locking system which I installed myself. The car does not have an alarm system.

A few thoughts:

- the symptoms that I see are very, very similar to the symptoms others see, so I guess it's a valid conclusion that they have the same reason.

- as my car doesn't have any fancy electronics like an alarm system, and the remote locking system is connected to nothing else but the doors, ignition and 12V power, we can rule out interaction with alarms or other comfort electronics as a reason.

- the symptoms disappear as sonn as I pull out the empeg. Range is back to normal, even if I do not change the batteries in the remote. So we can rule out bad batteries as reason.

- my car's head unit (Kenwood TV/FM/Navigation system) draws its power from the same point as both the empeg and the remote lock system. However, leaving the Kenwood running does not have an impact on the range. The Kenwood uses a big backlit LCD, so I'm very sure it draws more power than the empeg, which would cause a much bigger drop in voltage on the power lines. Btw, the current an empeg draws in standby mode should cause only *minimal* voltage drops, if any. So we can rule out voltage drops as a reason.

- In Germany, the only radio frequency that is available for things like remote door locks is 433MHz. So, as my remote door locking system is EU certified, I strongly assume (couldn't verify, unfortunately) that is operates at that frequency. I just performed an interesting experiment to check if the empeg has any influence on 433MHz devices: cordless mice use the same frequency, so I placed the base station of my Logitech cordless optical mouse on top of the empeg (the empeg running on AC). The distance between the base station/empeg and the mouse was around 1 meter. And indeed: as soon as the empeg was running or in standby mode, the mouse behaved erratically! When I disconnected the empeg from AC power without moving the base station, the effect went away.

Moving the base station more than a few centimeters away from the empeg also cured the problem, so the empeg doesn't radiate much. However, as the remote door locking sender uses very tiny batteries, it sends a *very* low power signal, which means the receiver in the car has to be *very* sensitive.

In my car, the receiver's antenna is some 50 cm away from the empeg. If I remember correctly, the power of an electromagnetical signal drops with distance to the second power. So, if I use the remote from 10 meters distance to the car, which is 20 times the distance the empeg has to the antenna, then even if the empeg sends with only 1/400th of the already very low-power remote signal, the antenna would receive them both with the same strength. This (admittedly not very detailled) calculation leads me to the conclusion that despite the empeg being FCC certified, it it very possible that it still interferes with weak remote door locking signals.

So, the next steps would have to be:

- find out with which power a remote usually sends. Can anybody who experiences the problems try to ask their car manufacturers or even try to find that in your manuals?

- try to get access to a measuring receiver to actually measure the radiation (frequency and power) of the empeg. Empeg folks: do you have any data from your FCC tests that could be helpful here?

- based on that data, do a more thorough calculation to see if my theory can be proved or disproved.

Daniel

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"My software never has bugs. It just develops random features."