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#1
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In message , John S
writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian -- Brian Howie |
#2
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On 10/1/2015 11:56 AM, Brian Howie wrote:
In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. |
#3
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On 10/1/2015 1:09 PM, John S wrote:
On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? -- Rick |
#4
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On 10/1/2015 12:18 PM, rickman wrote:
On 10/1/2015 1:09 PM, John S wrote: On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? I don't understand. Do you mean the antenna's feed point resistance of 20 ohms? My understanding of the installation is that the antenna is not directly connected to ground. Am I off track here? |
#5
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On 10/1/2015 1:21 PM, John S wrote:
On 10/1/2015 12:18 PM, rickman wrote: On 10/1/2015 1:09 PM, John S wrote: On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? I don't understand. Do you mean the antenna's feed point resistance of 20 ohms? My understanding of the installation is that the antenna is not directly connected to ground. Am I off track here? My bad. I didn't realize that was the antenna. But the capacitor could be bypassed with a large value resistor if static charge is your concern. A kohm should do the job without impacting the circuit significantly. But wait! Isn't the -130 cap also the antenna then? -- Rick |
#6
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On 10/1/2015 12:27 PM, rickman wrote:
On 10/1/2015 1:21 PM, John S wrote: On 10/1/2015 12:18 PM, rickman wrote: On 10/1/2015 1:09 PM, John S wrote: On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? I don't understand. Do you mean the antenna's feed point resistance of 20 ohms? My understanding of the installation is that the antenna is not directly connected to ground. Am I off track here? My bad. I didn't realize that was the antenna. But the capacitor could be bypassed with a large value resistor if static charge is your concern. A kohm should do the job without impacting the circuit significantly. But wait! Isn't the -130 cap also the antenna then? Yes. I guess I should have enclosed the combination in a box to represent the antenna. Sorry. |
#7
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On 10/1/2015 2:37 PM, John S wrote:
On 10/1/2015 12:27 PM, rickman wrote: On 10/1/2015 1:21 PM, John S wrote: On 10/1/2015 12:18 PM, rickman wrote: On 10/1/2015 1:09 PM, John S wrote: On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? I don't understand. Do you mean the antenna's feed point resistance of 20 ohms? My understanding of the installation is that the antenna is not directly connected to ground. Am I off track here? My bad. I didn't realize that was the antenna. But the capacitor could be bypassed with a large value resistor if static charge is your concern. A kohm should do the job without impacting the circuit significantly. But wait! Isn't the -130 cap also the antenna then? Yes. I guess I should have enclosed the combination in a box to represent the antenna. Sorry. So there is no cap, right? No cap, no worry. Oh, wait again. I see there are two circuits being discussed. So *that* cap can be bypassed with a 1 kohm resistor and not impact the circuit, right? -- Rick |
#8
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On 10/2/2015 2:34 AM, Jeff wrote:
___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. But it is connected by a 20 ohm resistor. How bad can that be? I don't understand. Do you mean the antenna's feed point resistance of 20 ohms? My understanding of the installation is that the antenna is not directly connected to ground. Am I off track here? My bad. I didn't realize that was the antenna. But the capacitor could be bypassed with a large value resistor if static charge is your concern. A kohm should do the job without impacting the circuit significantly. But wait! Isn't the -130 cap also the antenna then? What capacitor??????????? The 20-j130 is the impedance presented by the antenna at the feed point to gnd, there is no physical capacitor, the 4uH to gnd will provide a dc path for any static. Yes, that is what I said. "Isn't the -130 cap also the antenna then?" I was confused because of poor trimming when someone posted about a different matching network using a capacitor and a reply saying they don't like capacitors because they fail. With the context not being clear I thought they were talking about the capacitor in the diagram with the inductive matching network, but as you say, this capacitance is just part of the antenna. -- Rick |
#9
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In message , John S
writes On 10/1/2015 11:56 AM, Brian Howie wrote: In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. Brian Oh, yes of course. I try to avoid capacitors as much as I can because one end can float with static voltage while an inductor does not. I've had issues with nearby static lightning discharges. Just my paranoia. To each his own. Good point. Brian -- Brian Howie |
#10
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In message , Brian Howie
writes In message , John S writes On 10/1/2015 3:29 AM, Brian Howie wrote: In message , Wayne writes "Ian Jackson" wrote in message ... In message , rickman writes On 9/30/2015 12:57 PM, John S wrote: On 9/30/2015 10:12 AM, Ian Jackson wrote: In message , Jeff writes On 29/09/2015 14:31, Jerry Stuckle wrote: On 9/29/2015 4:40 AM, Jeff wrote: So let's get back to the original question. Was it ever really answered? I think it was made slightly more complicated by the fact that the antenna feedpoint impedance was not purely resistive, but was actually around 20-j130 (at 14 MHz), Was there any advantage in having the coax paralleled (both for 20 ohms resistive, and for 20-j130)? A quick model. A vertical antenna about 4.2m long with a wire radius of 0.5mm approximates to what you have . The devil is in the j130 If you use a 1.5uH series L the SWR for the parallel 50ohm line is 1.19: 1 and not a bad match over the band Expanding on the original question.... Antenna feedpoint approximately 20-j130 The ATU drives the antenna through about 15 feet of coax. Assuming that the ATU provides a +j130 conjugate match, does that leave the coax with a SWR of 50/20= 2.5:1? If so, then I will not bother with considering 2 parallel coax. No the line SWR is still about 36:1. If you run a bit of poke, you might melt the coax. If you want a single 50 ohm feed, extend the antenna to 5.7m ( ~50+ j87) and use a series C ~130pf to take out the the +j87. You have to do this at the antenna end. It goes without saying you need a good ground. Brian What do you think of this while leaving his antenna unchanged? 2.3uH ___ '-----o-----UUU--------------- .-. | ^ | | | | 20 | | C| ' '-' C| 4uH | C| 50 ohms | | --- | . -130--- | | | | v '-----o------------------------ (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) Yes that works too. Lots of ways to do it. I'm taking the opportunity to refresh my admittedly rudimentary skills with the Smith Chart - and in particular, single- and double-stub matching (little used for over 50 years!!). However, in Wayne's situation, the length of the coax is only 15'. On 14MHz, that's just over a quarterwave (taking the velocity factor into account). But even with a horrendous SWR, how much loss does this length of 213 coax have? It might be a lot more convenient to do all the matching in the warmth and comfort of the shack. I have done exactly this with a 130' inverted-L Marconi-type antenna, fed at the far end directly with around 100' of old (early 1960s) semi-airspaced TV trunk cable (with a good ground there). It worked fine on 160-80-40m (the bands I was interested in working), but it loaded up fine up to 10m - and as it seemed lively enough on receive, I'm sure it would have put out a reasonable signal. Although I eventually treated myself to a remote automatic ATU, I'm not convinced the system works any better than it did with the direct coax connection. -- Ian |
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