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#2
July 8th 15, 08:10 PM
posted to rec.radio.amateur.antenna
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An antenna question--43 ft vertical
On 7/8/2015 1:39 PM, wrote:
John S wrote: On 7/7/2015 1:58 PM, wrote: John S wrote: On 7/5/2015 7:21 PM, wrote: John S wrote: On 7/5/2015 5:24 PM, wrote: Roger Hayter wrote: wrote: The output impedance of an amateur transmitter IS approximately 50 Ohms as is trivially shown by reading the specifications for the transmitter which was designed and manufactured to match a 50 Ohm load. Do you think all those manuals are lies? You are starting with a false premise which makes everything after that false. A quick google demonstrates dozens of specification sheets that say the transmitter is designed for a 50 ohm load, and none that mention its output impedance. If the source impedance were other than 50 Ohms, the SWR with 50 Ohm coax and a 50 Ohm antenna would be high. It is not. Where is the source impedance found on a Smith chart? Also, if you have EZNEC, you will not find a place to specify source impedance but it will show the SWR. A Smith chart is normalized to 1. EZNEC allows you to set the impedance to anything you want and assumes the transmission line matches the transmitter. The EZNEC help file is very comprehensive. Please find any reference to your assertion that there is an assumption of source impedance there and provide information for us to verify your assertion. Why don't you email the author and get his take on your assumptions? Why don't YOU? You are the one in need of knowledge. If I do it and report back here you will just doubt it or find something else to argue about. Better you should do it first-hand. EZNEC calculates the SWR presented to the SOURCE which is usually placed at the antenna terminals. EZNEC also calculates the SWR presented to the SOURCE which can be modeled as a SOURCE at one end of a transmission line and the antenna at the other end. SWR is defined in terms of SOURCE impedance and LOAD impedance. No. It is defined as Vmax/Vmin on the line. Show an equation that defines SWR as the matching of the source to the line. I am tired of typing in the same equations over and over again. Then you are excused from participating. |
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#3
July 8th 15, 11:07 PM
posted to rec.radio.amateur.antenna
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An antenna question--43 ft vertical
John S wrote:
On 7/8/2015 1:39 PM, wrote: John S wrote: On 7/7/2015 1:58 PM, wrote: John S wrote: On 7/5/2015 7:21 PM, wrote: John S wrote: On 7/5/2015 5:24 PM, wrote: Roger Hayter wrote: wrote: The output impedance of an amateur transmitter IS approximately 50 Ohms as is trivially shown by reading the specifications for the transmitter which was designed and manufactured to match a 50 Ohm load. Do you think all those manuals are lies? You are starting with a false premise which makes everything after that false. A quick google demonstrates dozens of specification sheets that say the transmitter is designed for a 50 ohm load, and none that mention its output impedance. If the source impedance were other than 50 Ohms, the SWR with 50 Ohm coax and a 50 Ohm antenna would be high. It is not. Where is the source impedance found on a Smith chart? Also, if you have EZNEC, you will not find a place to specify source impedance but it will show the SWR. A Smith chart is normalized to 1. EZNEC allows you to set the impedance to anything you want and assumes the transmission line matches the transmitter. The EZNEC help file is very comprehensive. Please find any reference to your assertion that there is an assumption of source impedance there and provide information for us to verify your assertion. Why don't you email the author and get his take on your assumptions? Why don't YOU? You are the one in need of knowledge. If I do it and report back here you will just doubt it or find something else to argue about. Better you should do it first-hand. EZNEC calculates the SWR presented to the SOURCE which is usually placed at the antenna terminals. EZNEC also calculates the SWR presented to the SOURCE which can be modeled as a SOURCE at one end of a transmission line and the antenna at the other end. SWR is defined in terms of SOURCE impedance and LOAD impedance. No. It is defined as Vmax/Vmin on the line. Show an equation that defines SWR as the matching of the source to the line. OK, since you insist, one more time: SWR = (1 + |r|)/(1 - |r|) Where r = reflection coefficient. r = (Zl - Zo)/(Zl + Zo) Where Zl = complex load impedance and Zo = complex source impedance. https://en.wikipedia.org/wiki/Reflection_coefficient http://www.antenna-theory.com/tutori...nsmission3.php -- Jim Pennino |
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#4
July 9th 15, 07:09 PM
posted to rec.radio.amateur.antenna
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An antenna question--43 ft vertical
Jeff wrote:
No. It is defined as Vmax/Vmin on the line. Show an equation that defines SWR as the matching of the source to the line. OK, since you insist, one more time: SWR = (1 + |r|)/(1 - |r|) Where r = reflection coefficient. r = (Zl - Zo)/(Zl + Zo) Where Zl = complex load impedance and Zo = complex source impedance. https://en.wikipedia.org/wiki/Reflection_coefficient http://www.antenna-theory.com/tutori...nsmission3.php And once more time, the formula linking VSWR to Reflection coefficient uses ONLY the MAGNITUDE of the Reflection Coefficient |r|, taking the magnitude removes the phase component. The magnitude DEPENDS on the phase component. Secondly the formula linking VSWR to Reflection Coefficient is NOT a definition of VSWR, it is merely a formula that links 2 related quantities. So is power P=EI or P=E^2/R? Which is the "official" definition? -- Jim Pennino |
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#5
July 8th 15, 10:23 PM
posted to rec.radio.amateur.antenna
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An antenna question--43 ft vertical
wrote:
John S wrote: On 7/7/2015 1:58 PM, wrote: John S wrote: On 7/5/2015 7:21 PM, wrote: John S wrote: On 7/5/2015 5:24 PM, wrote: Roger Hayter wrote: wrote: The output impedance of an amateur transmitter IS approximately 50 Ohms as is trivially shown by reading the specifications for the transmitter which was designed and manufactured to match a 50 Ohm load. Do you think all those manuals are lies? You are starting with a false premise which makes everything after that false. A quick google demonstrates dozens of specification sheets that say the transmitter is designed for a 50 ohm load, and none that mention its output impedance. If the source impedance were other than 50 Ohms, the SWR with 50 Ohm coax and a 50 Ohm antenna would be high. It is not. Where is the source impedance found on a Smith chart? Also, if you have EZNEC, you will not find a place to specify source impedance but it will show the SWR. A Smith chart is normalized to 1. EZNEC allows you to set the impedance to anything you want and assumes the transmission line matches the transmitter. The EZNEC help file is very comprehensive. Please find any reference to your assertion that there is an assumption of source impedance there and provide information for us to verify your assertion. Why don't you email the author and get his take on your assumptions? Why don't YOU? You are the one in need of knowledge. If I do it and report back here you will just doubt it or find something else to argue about. Better you should do it first-hand. EZNEC calculates the SWR presented to the SOURCE which is usually placed at the antenna terminals. EZNEC also calculates the SWR presented to the SOURCE which can be modeled as a SOURCE at one end of a transmission line and the antenna at the other end. SWR is defined in terms of SOURCE impedance and LOAD impedance. I am tired of typing in the same equations over and over again. Zo is the characteristiic impedance of the transmission line and nothing to do with the source impedance of whatever generator is supplying power to the system. -- Roger Hayter |
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#6
July 8th 15, 11:11 PM
posted to rec.radio.amateur.antenna
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An antenna question--43 ft vertical
Roger Hayter wrote:
wrote: John S wrote: On 7/7/2015 1:58 PM, wrote: John S wrote: On 7/5/2015 7:21 PM, wrote: John S wrote: On 7/5/2015 5:24 PM, wrote: Roger Hayter wrote: wrote: The output impedance of an amateur transmitter IS approximately 50 Ohms as is trivially shown by reading the specifications for the transmitter which was designed and manufactured to match a 50 Ohm load. Do you think all those manuals are lies? You are starting with a false premise which makes everything after that false. A quick google demonstrates dozens of specification sheets that say the transmitter is designed for a 50 ohm load, and none that mention its output impedance. If the source impedance were other than 50 Ohms, the SWR with 50 Ohm coax and a 50 Ohm antenna would be high. It is not. Where is the source impedance found on a Smith chart? Also, if you have EZNEC, you will not find a place to specify source impedance but it will show the SWR. A Smith chart is normalized to 1. EZNEC allows you to set the impedance to anything you want and assumes the transmission line matches the transmitter. The EZNEC help file is very comprehensive. Please find any reference to your assertion that there is an assumption of source impedance there and provide information for us to verify your assertion. Why don't you email the author and get his take on your assumptions? Why don't YOU? You are the one in need of knowledge. If I do it and report back here you will just doubt it or find something else to argue about. Better you should do it first-hand. EZNEC calculates the SWR presented to the SOURCE which is usually placed at the antenna terminals. EZNEC also calculates the SWR presented to the SOURCE which can be modeled as a SOURCE at one end of a transmission line and the antenna at the other end. SWR is defined in terms of SOURCE impedance and LOAD impedance. I am tired of typing in the same equations over and over again. Zo is the characteristiic impedance of the transmission line and nothing to do with the source impedance of whatever generator is supplying power to the system. No, Zo is the source impedance and it is irrelevant what the source physically is and has nothing to do with power. https://en.wikipedia.org/wiki/Reflection_coefficient http://www.antenna-theory.com/tutori...nsmission3.php -- Jim Pennino |
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