ok folks, time for a simple lesson in physics.
first off, any metallic case, be it aluminum, steel, titanium, or any alloy of these materials, is dense. all metals have dense molecular construction that gives it the properties they exhibit in hardness and tensile strength, some more than others. because of this, it also makes them great conductors for both heat and electricity. however, it also makes them all great shielding agents against radiation, of course the more dense the metal compound, the better… lead being one of the better metals for shielding from radiation.
now this brings about the topic for radio transmission, what makes your cell phone “wireless.” like any other form of radiation, these metallic compounds, depending on their density, will cause an attenuating effect of the desired radiation if the radiating device, in this case the antenna, is covered by a case made of these materials. it doesnt matter one bit if the metal comes into contact with the antenna or not; the signal will be reduced as it’s unable to pass through the shielding material.
therefore, ALL metallic cases will attenuate the signal on ALL cellphones. it’s simply due to the shielding effects of the metal compound of the case. in fact, even composite cases will affect the signal, although to a much lesser degree to the point of being nearly unnoticeable. yes, some of the most expensive cases are machined from aluminum or titanium and they look awesome in some cases, but they will cause signal attenuation that is unpreventable no matter how it’s designed. the only way to prevent this is to ground the case into the antenna, therefore acting as an extension of the antenna and extending radiation itself. because most cell phones have an internally placed antenna, this is impossible. despite the advertising of the iPhone claiming integration of the antenna into the structural support exposed as a steel band around the perimeter of the device, the radiator is still within the body of the device and simple contact between a metallic case and the midframe will NOT negate the issue of signal shielding, much less improve signal radiation. in fact, since you’re now shielding the primary radiating component, you’re going to experience degradation of the signal.
this is basic physics and is undeniable. dont blame the designers of these cases for anything other than designing something that works to reduce signal performance. this is something everyone should already know and have taken into account before their purchase of a metallic case. any manufacturer who claims to have worked around, solved, or even improves performance is trading on fraudulent claims. ignorance is no excuse.