I recognize this topic has been discussed in the past with input from the scientific community. Having listened to the show today, and having read the research done on it, I have a few comments and questions.
In looking at the study done by Remcom, my question is about health issues. Remcom determined that indeed pointing the keyless entry unit toward ones face increased the signal strength. Usually, with radio transmitters, safety concerns dictate to lessen the amount of signal exposure to our bodies, when it can be so directed (cell phones, cordless phones, microwave, etc.). Is it possible the reason why the transmitter antenna is orientated toward the vehicle rather than toward our bodies, even if the signal strength to the car may be increased doing so, is a potential health risk? Finally, in regard to car keyless entry units, perhaps a new battery in the unit might give it more distance even when pointed as it was designed.
Part II: TV remote controls got thrown into this discussion. They use a completely different technology than keyless entry devices for vehicles. The vast majority of remote controls for household electronics use infrared light transmitters and receivers, rather than radio waves. Interestingly, Ray (or was it Tom?) got it correct when he spoke of dispersion of the source. The infrared signal from most remotes is produced by a single LED (Light Emitting Diode) source. LEDs have this habit of being very directional. In light this is referred to as “collimated”. It is one of the problems with using LED light sources as general lighting or flashlights, in that the light follows a very restricted (non-dispersed) path, so while they are great at targeted lighting, they leave the rest of the area surrounding them dark. The fix is a diffuser, but diffusers also scatter light and make it less bright as a result. That is why LED lighting for homes and flashlights have many LED light sources over a broad surface to try to spread the light around more. Getting back to remote controls, the manufacturers generally are more concerned with providing maximum distance at minimum power requirement, so the LED is usually not diffused, and indeed if one points the remote accurately toward the receiver in the device (TV, DVD, CD player, etc) it works well. But the problem is when one misses the receiver window, or there is something blocking the direct line between the remote and the receiver. In those situations, if the receiver is sensitive enough, “bouncing” the infrared light source off of a wall, or your forehead, may allow the remote to activate the receiver without a direct “hit”, as the light gets bounced around and may reach the receiver at numerous angles. The reason this “bounced light approach” doesn’t work well when pointing the remote toward the device is because, there is inadequate surface area facing toward the receiver to diffuse or disperse the light to the receiver, and by the time it gets rebounced from the opposite wall the intensity is too low. (Again Ray(?) (one of these days I’ll remember who is who) got it correct).
So, laugh all you like Tom (or was it Ray ;-)), but Ray (or was it Tom) had it correct when he said the remote got dispersed (diffused) and that’s why it worked “better” when bounced off a close object than when incorrectly aimed, as “off the wall” as that might sound…
