So in an attempt to figure out why this one Sylvania Downlight was getting disconnected occasionally, I took it apart. Inside the metal shell, I found the on board zigbee antenna.
I'll be the first to admit never passing a wireless technology course, but imbedding an antenna inside a metal shell, which will likely be put in a metal downlight housing, would appear to be a poor choice. idea. Unless the metal is a special type of transmittium? yes I just made up that word.
On top of that, they had placed a heavy paper sticker right on the antenna traces. Don't antenna vibrate? Could the paper affect the resonance of that tiny antenna? Gonna put it all back together and see if any perceptible difference in LQI.
I know inovelli made efforts to move their switch's antenna to right up front, away from the ,often metal, wall boxes, using a tiny wire to traverse to make the antenna up front, right under the paddle.
The sticker, at least, is not going to be a problem. Many antenna wires are already covered in tight plastic insulation... Or think about antennas on PCBs, where metal traces are bonded to the board.
probably the same with their white temp adjustable bulbs.. i removed them all and switched over to hue ones and just like your downlights they would all periodically fall of the mesh.. and to make matters worse they were repeaters ... so objviously when that happened other devices were not happy.
For what it's worth, what I see there makes a lot of sense. That enclosure looks pretty metallic to me, which RF signals are not going to penetrate either in, or out. Having the antenna close to the lens, especially in a downlight, will give this device the best opportunity to communicate. The signal will pass through the lens and label easily, but buried up in the casing without some form of external antenna would be pointless.
A similar comparison is the Leviton Z-Wave receptacles I used to have. Original non-Plus versions had the antenna back in the guts of the device. In Canada, we sure love(d) metallic device boxes (although there has been a shift toward non-metallic). I couldn't get these things to establish a reliable connection, and in some cases any connection, regardless of efforts I made such as increasing the quantity of devices in the mesh and installing many pointing in the general direction of other devices. Once I switched to the GE/Jasco product, a closer look revealed the antenna being routed toward the front of the receptacle. Still not perfect in a metal box, but much better. ! Eventually I changed many of device boxes to a non-metallic version to further solidify the mesh.
In the case of your light, they need the metal housing for heat dissipation so having the antenna protrude downward and closer to the lens was good engineering. Although I'm talking both Zigbee and Z-Wave devices here, the principal remains that metal shielding is going to impede RF signals.
yes I just made up that word.
