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#11
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Dave Oldridge wrote:
My question is one of Physics. Lest anyone think I have invented something new, I'm sure Walter Maxwell was doing these sorts of Smith Chart calculations while I was in high school. Given the following 1/4WL resonant stub with Z01 = 600 ohms and Z02 = 4000 ohms: Source----Z01A----x----Z02----y----Z01B----open Boundary conditions a The feedlines are lossless. The source sees zero ohms. The Z01A length is 45 degrees. The Z02 length is 45 degrees. How long is the Z01B length? This is a problem easily solved by using the outside circles of two Smith Charts, one normalized for 600 ohms and the other normalized for 4000 ohms. The procedure is: Assuming the source is seeing zero ohms, calculate the impedance at 'x'. Plot that impedance on a Z02 Smith Chart. Calculate the impedance at point 'y' of the Z02 length. Plot that impedance on the first Smith Chart and see how long Z01B needs to be to reach to infinity. -- 73, Cecil http://www.qsl.net/w5dxp |
#12
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Cecil Moore wrote:
Dave wrote: Cecil --- you are begging the question!! Of course I am, nobody knows *why* things are the way they are. There is no 'why' built into quantum mechanics. There is only probability. Why does one photon wind up in an inner interference ring and one wind up in an outer interference ring? Nobody knows. Methinks you have left the world of deterministic Physics and moved into Quantum Physics. Such comments do not contribute to the answer. You are not using Quantum mechanics to try to explain to me what is happening. You are using transmission line models. Stick to the transmission line model. I thought antenna EM Physics was deterministic. - - - - your model. You stated: "Anything done below the coil affects the number of degrees subtracted from the antenna by the bottom element to coil interface. Anything done to the stinger affects the number of degrees added to the antenna by the coil to stinger interface. For a given element delta length, the number-of-degrees-added effect is greater than the number- of-degrees-subtracted effect." The 4 inch spring is approximately 0.646 degrees long at 5.3 MHz. Original: Source-----Z01A-----+-----Z02-----+-----Z01B-----open Case #1: Source-----Z01A-----+-----Z02-----+-0.646-+-----Z01B-----open Case #2: Source-----Z01A-----+-0.646-+-----Z02-----+-----Z01B-----open Z01A has not changed. Z02 has not changed. Z01B has not changed. [The L/D ratios for these components have remained the same and the Zo of each element is therefore the same.] The physical characteristics of 0.646 have not changed. The Capacitance to the coil is the same in either case. Only the location has changed. Do you claim the complex impedance of 0.646[case 1] is different from the complex impedance of 0.646[case 2]. Why? Or, do you claim the net Z01B + 0.646[Case 1} is now electrically longer, in degrees, than Z01A + 0.646[case 2]. Why? |
#13
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Dave wrote:
Or, do you claim the net Z01B + 0.646[Case 1} is now electrically longer, in degrees, than Z01A + 0.646[case 2]. Why? I already explained how to prove to yourself why those two cases are different. Please perform the Smith Chart gymnastics and then report your findings. -- 73, Cecil http://www.qsl.net/w5dxp |
#14
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Cecil Moore wrote:
Dave wrote: Or, do you claim the net Z01B + 0.646[Case 1} is now electrically longer, in degrees, than Z01A + 0.646[case 2]. Why? I already explained how to prove to yourself why those two cases are different. Please perform the Smith Chart gymnastics and then report your findings. If one takes one foot of stinger and transfers it to the base element section, the antenna length remains the same and the resonant frequency increases. I assume you already knew that. So of course, 0.646 is electrically longer when it is on top of the coil than when it is on the bottom of the coil. The Smith Chart exercise will show why that is true. -- 73, Cecil http://www.qsl.net/w5dxp |
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