So a satellite dish reflects as well as absorbs the RF just like a TV antenna does?
What exactly is happening when a RF wave hits a satellite dish made from wire mesh? Is it only reflecting part of the wave? How does it make a predictable bounce to the receiver in the center? I watched satellite TV from that dish for years when I was young so I know it worked, I just want to know why it worked.
Mostly it reflects. It would absorb only if the elements had a higher resistance than the wires of the mesh or dish. Mesh will absorb some of the energy but most of it is reflected. The shape of the dish is the biggest factor, it has to be a parabolic shape or some variation of that shape. The standard sat dish of today uses an offset parabola designed in such a way as the actual receive antenna elements are out of the way of the incoming RF. If you ever looked through a reflector telescope, you see a mirror in front canted off 45 degrees and then more optics to focus the incoming light. That little mirror effects the image for one thing by just reducing some of the light reaching the actual reflector mirror and the supports of the small mirror adds artifacts to the optical path.
It is similar in a TV Sat dish. If we used the old fashioned steerable dish, you remember the big ones, 6 to 8 feet in diameter? The actual pickup array is right in line with the incoming RF so it blocks a small amount of the receive signal. Not a huge deal with an 8 foot dish, the difference of the block Vs no block would not be detectable.
On the tiny Sat dishes, however, the receive elements are around the same size as the old big dishes. So a dish of say one foot diameter with the receive elements in place would block a rather large amount of the incoming signal. So they use an offset parabolic curve so the whole area of the dish sends the RF to the receive elements without those elements interfering with the signal. But it is basically a parabolic curve which focuses the RF or optical energy to a point, limited by diffraction but generally pretty good at focusing RF or light.
So you got the idea that ELF may not be blocked by a mesh but it will be stopped by a solid panel of copper which is what professional level Faraday cages use so NO RF gets through no matter the wavelength. For instance, a 3000 mile long high voltage transmission line loses about 7 percent of its energy in that long trip from source to load. Most of that loss is in the resistance of the wires conducting the energy but some of it is actually transmitted, and a 3000 mile long wire is a fair imitation of an antenna at the frequency we use, 60 Hertz, 60 cycles per second.
At that frequency, the wavelength is about 3100 miles and the wire could be something like that length so it would be an antenna, of some efficiency so the entire US is saturated with some low level of 60 hertz radiation. Also the same from house wiring but much less effectively turned into actual RF but still some of it is transmitted.
That kind of wavelength is what the subs use to get messages to the sub when other methods are dead. If a sub is 1000 feet underwater no RF of normal wavelengths will penetrate that deep but 60 Hertz will. Of course such a low frequency means there is a limit as to how much information can be stuffed down that small hole. It would basically be a Morse code link, a few words per second, maybe 20 WPM or so and that would be the word to every sub in the world so they would have a code for a single sub and they would have to wait their place in line to get their particular message.
Really slow but no weather, clouds, storms, lightning or such will stop that signal getting through.