Frequently asked questions
Which fields are shielded by the shielded cables ? The electric field, the magnetic field or both ?
A good shielded cable blocks almost completely the electric field of 50 Hz frequency which is created around every electric cable inserted in a active socket, even when the devices are turned off and even when the cable is disconnected from the device.
A shielded cable reduces partially also the magnetic field created by the electric currents in the cable, which is quite small in common cases since the currents are not very high.
Then the bigger effect of the shielded cable is to remove the alternate electric field, which is the most harmful in this case.
Do I have to put the shield of the cable to ground or is it already grounded ?
The metal shield in the cable is already connected to the ground wire where needed, so you don't have to attach anything else, just be sure that the grounding system of you electric network is OK.
The shielded cable is like something that forces a stream of water to go along the tube, but the water will be free at the end of the tube, isn't it ?
First there is nothing like a fluid in electromagnetic fields, the model of the stream of water in a tube is completely wrong, sorry.
The metal shield around the conductors reduces greatly the electric field outside the cable. Then in the device connected to the cable the alternate voltage at 220 V (or 120 V) is converted into a direct voltage of 12 V or less, in the interior of an iron chassis that shields partially both electric and magnetic fields.
The shield around the electric wires alters the electric field in such a way that the electric field outside the cable is almost zeroed. For this reason cable shielding is intensively used in professional applications, and in high power audio systems, where alternate electric fields would cause unbearable background noise.
Instead of shielded cables, wouldn't it be better and cheaper a single metal plate placed over the cables on the floor ?
The metal plate cannot shield enough the low frequency electric field, it has to make a closed structure around the whole length of the cable.
Furthermore if you build such a metal box it would be rather heavy and difficult to move, while a cable with inner shield is still flexible and movable. Once you have the low rectangular box under the table, what do you do if you need to move the cables in another part of the room ?
Finally, the metal box would shield only the part of the cables that are lying on the floor, how can you shield the part that hang from the tables ?
Is the backlight of the modified LCD monitors really uniform ?
The backlight of the modified LCD monitors is almost perfectly uniform, some
very light non-uniformity can be seen only at few millimeters from the top and
bottom borders where the LEDs are installed, and it's definitely not a problem.
What sizes of LCD monitor can be modified with your LED backlight ?
The LED strips that we have designed could in theory provide enough light for LCD panels of 40" Widescreen and more, but we haven't tested so far in practice. However there should be no problem at all for 24" Widescreen displays.
Could OLED displays be better in terms of EMF ?
An OLED display does not have a backlight, since the display elements produce the light, so there is no backlight circuit, and this saves quite a lot of EMF.
But the OLED cells need electronic voltage and current to generate light, and this voltage is not "clean" of course, it is provided by a small electronic circuit, a DC-DC converter, so it contains a lot of EM noise, every pixel has it, so the entire panel with millions of pixels emits some EMF.
The other parts of a OLED display are more or less the same of a LCD display, there is a circuit board which converts the video signal from the HDMI, DVI or other format to the digital waves needed by the OLED pixels, just like it is in the LCD displays. This board generates quite a lot of EMF, and the only way to stop this EMF is to shield this board with thick metal enclosure without apertures.
Finally, an OLED display would have a power supply board which converts the AC voltage into various DC voltages, for the mainboard and for the OLED panel, and this is another big source if EMF, and the only way to avoid it is to remove it completely. If the OLED display has an external power adapter that will be a SMPS for sure, which generates a lot of EM noise into the monitor and also radiates around itself.
So in conclusion OLED monitors will be better than current LCD monitors in terms of EMF, but they would not be better than my modified LCD monitor.
Is it possible to shield a laptop?
Shielding a laptop is not possible in practice because today's laptops are extremely compact and there isn't any space available inside for the shielding, maybe there is just a thin space for a layer of aluminum foil, but anyway it would be too little to achieve a good result. Maybe some shielding foil can be applied on the exterior, but the keyboard has to remain uncovered, so the user's hands are still reached by the EM fields, and there must be many openings for the various connectors, and the ventilation, so the result is not good at all.
If you use the laptop on a desk, then you can move it away and attach an external keyboard to it, and maybe this keyboard can be shielded, or maybe it already has low electromagnetic emissions.
What are the most common symptoms of EMF ?
Some people have pain in their hand and fingers when they use a typical computer mouse or a keyboard.
Some people have pain and other bad symptoms in their heads when they use a typical computer monitor.
Some people have lots of bad symptoms in their heads and whole body when they turn on the Wi Fi
Lots of people have generally bad health, bad sleep, bad performances because they live constantly in a EMF filled environment.
Some people feel bad symptoms due to the wired network device, like DSL modem-router, fiber optic network terminal.
Lots of people have strong bad symptoms when they are near to a cellphone or smartphones.
Some people feel pain in their heads and chest when they move around in the city or the countryside and there are cellphone antennas around.
Some people feel pain in their hand and finger tip when they touch the screen of a smartphone or tablet.