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![]() "Cecil Moore" napisal w wiadomosci ... On Feb 26, 12:21 pm, "Szczepan Bialek" wrote: So we also can say that aether consists of ordinary particles. It depends upon how one defines "ordinary". The structure of free space has existed since the big bang but man has only recently discovered the structure and is still somewhat ignorant of its configuration and characteristics. There is some evidence that the structure of space in which ordinary non-dark matter and non-dark energy exists, is made up of dark matter and dark energy. I prefer this: "It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. We have assumed that each stellar system in evolutions throws off electric corpuscles into space. It does not seem unreasonable therefore to think that the greater part of the material masses in the universe is found, not in the solar [sic] systems or nebulae, but in 'empty' space" (Birkeland 1913). Thorndike (1930) noted that "it could scarcely have been believed that the enormous gaps between the stars are completely void. Terrestrial aurorae are not improbably excited by charged particles from the Sun emitted by the Sun. If the millions of other stars are also ejecting ions, as is undoubtedly true, no absolute vacuum can exist within the galaxy." A loop antenna' is a radio antenna consisting of a loop of wire or other conductor with its ends connected to a two-wire transmission line. They have a radiation pattern similar to a dipole antenna" I do not understand. A loop, like a dipole, is a standing wave antenna with a characteristic impedance in the few hundred ohms, e.g. 600 ohms. The reflections on a standing wave antenna have to originate from an impedance discontinuity. The feedpoint impedance of a standing wave antenna is Zfp = (Vfor + Vref)/(Ifor + Iref) where phasor math is used. Let's assume that the feedpoint impedance is 100+j0 ohms and the antenna is being fed with Z0=100 ohm feedline. There are no reflections on the feedline which means a Z0-match to 100 ohms exists at the antenna feedpoint. Assume the characteristic impedance of the antenna wire over ground is 600 ohms. The 600 ohm to 100 ohm impedance discontinuity at the feedpoint creates a reflection coefficient of 0.7. That's where the reflections on the standing wave loop antenna are coming from. One reason the feedpoint of a resonant loop is higher than for a 1/2WL dipole is that the reflection coefficient for the loop is 0.7 while the reflection coefficient for a dipole is obviously 1.0 at the ends of the dipole. The concept may be easier to understand using a rhombic example. A terminated rhombic is terminated in the characteristic impedance of the antenna wire above ground, e.g. 600 ohms, which eliminates reflections on the antenna and turns it into a traveling wave antenna where the feedpoint impedance of the antenna is equal to the characteristic impedance of the antenna over a wide frequency range, i.e. Zfp = Vfor/Ifor, independent of frequency. Removing the termination turns the rhombic antenna into a standing wave antenna and the feedpoint impedance becomes Zfp = (Vfor + Vref)/ (Ifor + Iref), i.e. the feedpoint impedance is frequency dependent like other standing wave antennas. See: http://paws.kettering.edu/~drussell/Phys302/09.html "Electromagnetic pulse in a coaxial cable reflects from a short circuit with the opposite polarity (upside down)" A loop is like a short circuit. What do a Electromagnetic pulse in a loop? It simply travel trough the loop and looks like the "reflected with the opposite polarity ". Why am I wrong and D. Russell is right? S* -- |
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