What a badly written piece of text.
"Overwhelms the contaminations" jeez! what a drama queen!
"High voltage rupture" Yes one of the early cables did fail due to too much voltage being used to try and overcome the losses.
The voltage used was too high for the dielectric (insulation) in the cable, and so the insulation broke down.
Why didn't the idiot who wrote that text just say that!
I have never heard that expression, can you put some context to it?is there some phenomenon called 'power leakage'
I have never heard that expression, can you put some context to it?
JimB
A baseband radio transmitter would be very impractical. You are talking about antennae the length of countries and small moons. It's not impossible in principle, but completely impractical.
JimB said:Polarisation.
If the elements of the antenna are horizontal, it is said to be horizontally polarised.
Similarly, if the elements of the antenna are vertical, it is said to be vertically polarised.
The antennas at both ends of a link should be of the same polarisation, otherwise there will be a BIG loss of signal (in practice, about 20 or 30dB).
The same it true for whip antennas!
The whip antenna on a broadcast radio litening to a local station has so much signal that the loss due to incorrect polarisaion is not usually noticed.
Another issue is the wavelength range changes by 1 order of magnitude. When you modulate, the wavelength is determined by the high frequency carrier and the signal content does not changes this appreciably.
Yes it is totally impractical.Is this really completely impractical? Do you mean to say it won't work at all? In reply to Q4 here, Jim said,
No, it is a fairly lame brain moronic answer.Is the answer below a good one?
All EM waves undergo three physical phenomenons which are reflection, refraction (bending due to change in transmission medium), and diffraction (spreading after encountering an obstacle). Suppose you point a powerful dot-thin red laser beam at moon, ignore all the air and water particles etc. That dot-thin beam will become quite a huge size red spot after reaching the surface of moon. Because when the beam exits the aperture, it sees it an obstacle and starts spreading. Another very important phenomena related to an EM wave is that of ability of penetrating solids such as concrete etc. (check first four links)
The first part is my understanding of line-of-sight too, but you are correct to point out that terminology is rarely precise, and other meanings can come into play.To most people line-of-sight communication means that two communicating devices should be able to establish a direct communication path between them without any obstacle therein. For example, before Bluetooth technology became prevalent, infrared communication between two cell phones required that the infrared sensors of both phones should be able to see each other. But such an understanding of line-of-sight communication is not all correct.
At this point also read through post #12 and #13 above, especially go through the links given in post #12. I believe both AM and FM are line-of-sight communications. AM signal can have global reach because of reflection from ionosphere. On the other hand, FM signal, which has higher frequency, doesn't reflect well from ionosphere and therefore has small range. If the earth were a plain surface which is to say no trees, building, mountains, air molecules, water particles, atmospheric layers etc. then you won't be able hear anything on your radio unless your radio and transmitting antenna can see each other. Because it would mean no reflection which play a dominant role if spreading of a signal. Q1: Do I have my understanding correct up to this point?
I'm not sure why you mention reflection alone. Reflection and transmission go hand-in-hand and there are absorption/scattering effects and diffraction/refraction effects as you mentioned.Infrared radiation has higher frequency range than that of AM and FM but it is comparatively bad at reflection etc. I'm saying this from my practical experience. Likewise, FM covers higher frequency range than AM and it is not as good at reflection as AM is.
Yes or course, but it is not simple. Various materials (conductors, dielectrics, and materials with complex conductivity/permittivity) would have very different characteristics. There is also strong dependence on incident angle. There are also absorption, scattering and other effects. Again I would say, think about what you see with visible light and all the variety with different materials.Q2: Is there some relation between frequency and reflection?
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