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On Mon, 6 Sep 2004 23:15:24 -0500, (Richard
Harrison) wrote: The newly minted RF and the twice reflected RF are similar, both having their volts and amps in-phase. Hi Richard, In a reality of 359 other possible phase angles, how does a transmitter happen to always be "in-phase" to any reflection? 73's Richard Clark, KB7QHC |
Bob Nielsen wrote:
On Mon, 06 Sep 2004 22:26:16 GMT, Walter Maxwell wrote: However, what happened to the Rolls-Royce? Did the Queen boot it out? As I recall it from my pre-teen days, it was definitely a Brit. And how did it manage to land in Deutchland? Or did Neville Chamberlin manipulate this one too? Still made in Britain, but owned by BMW, who also make the recent incarnation of Minis. The original MGs were built right here in Abingdon-on-Thames, and the big factory where the Minis are made is just up the road in Oxford. Lots of local people either are or have worked in the car industry... and some of them are also hams. Even when R-R Motors was an independent company, it used part of the big Oxford factory. That much larger company eventually bought R-R, but in turn has done deals in which first Honda and then BMW provided transfusions of new technology in return for a large share of the company itself. However, the company still makes its own cars under the name Austin Rover. R-R Motors has always been a separate operation, with very different ways of doing things. For example, all the stories you've heard about countless coats of paint, each one hand-applied and hand-rubbed, are true. The comforting thing is that down at the other end of the factory, cars for the rest of us are being stamped out with modern high-tech, high-bake paint jobs that will wear far better. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Richard Harrison wrote:
Who makes the Rolls-Royce jet engines now? Rolls-Royce do. The aero engine operation separated from the original car building operation in the 1970s. When the two companies split, they were smart enough to let both keep the hugely valuable brand name - unlike Hewlett-Packard. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
"Ian White, G3SEK" wrote in message ... Richard Harrison wrote: Who makes the Rolls-Royce jet engines now? Rolls-Royce do. The aero engine operation separated from the original car building operation in the 1970s. When the two companies split, they were smart enough to let both keep the hugely valuable brand name - unlike Hewlett-Packard. -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek Ummm, what part of hijack & pillage are you uncomfortable about? Ed wb6wsn |
Ed Price wrote:
Who makes the Rolls-Royce jet engines now? Rolls-Royce do. The aero engine operation separated from the original car building operation in the 1970s. When the two companies split, they were smart enough to let both keep the hugely valuable brand name - unlike Hewlett-Packard. Ummm, what part of hijack & pillage are you uncomfortable about? No problem with the old "High-Priced" brand name at all - it's the other one... -- 73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Richard Harrison wrote:
The newly minted RF and the twice reflected RF are similar, both having their volts and amps in-phase. So, the similar RF constituents merge to have a go at the reflection point. Wonder why we have protection circuitry in transmitters? The superposed forward voltage and reflected voltage can damage an unprotected transmitter. The superposed forward current and reflected current can cause over heating in an unprotected transmitter. The transmitter sees whatever impedance it sees and that impedance can be highly reactive. The superposed voltage can be high or low. The superposed current can be high or low. The phase between the superposed voltage and superposed current can have lots of values. Just a for instance - assume the transmitter is putting out 70.7v in phase with 1.4a at zero deg. The arriving reflected wave is 50v at 90 deg and 1.0a at -90 deg. The load seen by the transmitter is 86.6v at 35 deg and 1.72a at -35 deg. Over voltage and over current exist at the transmitter output. The forward power is 100w and the reflected power is 50w. The net power being delivered to the reactive "load" seen by the transmitter is 86.6*1.72*cos(70.4) = 50w. The math model is trying to dictate reality. It is supposed to be exactly the opposite. There is no magic barrier that automatically rejects reflected energy from a transmitter. Reflected energy arriving at the transmitter can drastically alter the impedance away from the designed-for load impedance. The transmitter sees one of the transformed impedances that exists on the SWR circle. Note that the problem disappears in a matched system where reflected energy is not allowed to reach the transmitter. -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
Richard Clark wrote:
"In a reality of 359 other possible phase angles, how does a transmitter happen to always be in-phase to any reflection?" Connect any generator to any resistor, and current in the resistor is in-phase with the applied voltage. The Zo of the common transmission line is a reasonably good resistance. At radio frequencies, Zo is independent of frequency. The current in the incident wave is always in-phase with the voltage applied to a transmission line. The current in the reflected wave is always 180-degrees out-of-phase with the reflected voltage. It makes no difference which was inverted by reflection, the volts or tha amps, one, and only one, of them was flipped upside down. The transmission line can and does handle the reflected wave. Standing waves display interference between incident and reflected waves whiich ideally have in-phase and out-of-phase constituents. The fact that the Bird wattmeter works is evidence that the theory is correct at least until a better theory replaces existing theory. Best regards, Richard Harrison, KB5WZI |
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Cecil, W5DXP wrote:
"The superposed forward voltage and reflected voltage can damage an unprotected transmitter." To do so, they would be in-phase and not out-of-phase. Entirely possible if the transmission line is the right length. If the reflected volts are in the same phase as the newly munted volts, which are larger? With a reflection coefficient of 1, and a lossless line, the open-circuit value of transmitter volts would face some lower value of line volts on opposite ends of the internal impedance of the transmitter. Which way does the current flow? Theory is that it flows from the higher to the lower. That is, from the transmitter to the line. Best regards, Richard Harrison, KB5WZI |
Richard Clark wrote:
In a world of mismatches, how does it happen that the transmitter always sees an in-phase, resistive load?" It doesn`t. You can put a capacitor directly across its output terminals, and the transmitter will energize the capacitor. But, a transmission line is not a capacitor unless it is a short open circuit, or the equivalent. A transmission line is a distributed network of inductance and capacitance. This network transfers emergy in bucket brigade fashion. The "brigade" presents a resistive impedance to both the incident wave and to the reflected wave. Zo is an enforcer. Best regards, Richard Harrison, KB5WZI |
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