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#1
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![]() "John Smith" wrote in message ... JB wrote: ... Ya I know, I didn't get into the how. How much is the first thing you need to be aware of. You may also find this picture of a 1:1 guanella balun of interest. Notice the "crossover" which alters the direction of the common winding between sides of the core ... Regards, JS There ya go. One of the problems of breaking up the path to ground on the shield is that now static can build up. If you can provide a way to bleed off the charges that build up on both halves, while breaking up the shield currents, now you have made it worthwhile. But when you guys start discussing off center fed dipoles, I step aside. I have computers in the shack. I have better luck with fan dipoles. Also running a Butternut vertical. Works a lot better than a 4btv, but a pain to get it right on all bands. Thanks Also liked the other pdfs presented. I never have time to read them all because of constant interruption around here. Back to work. |
#2
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JB wrote:
... There ya go. One of the problems of breaking up the path to ground on the shield is that now static can build up. If you can provide a way to bleed off the charges that build up on both halves, while breaking up the shield currents, now you have made it worthwhile. But when you guys start discussing off center fed dipoles, I step aside. I have computers in the shack. I have better luck with fan dipoles. Also running a Butternut vertical. Works a lot better than a 4btv, but a pain to get it right on all bands. Thanks Also liked the other pdfs presented. I never have time to read them all because of constant interruption around here. Back to work. OCF antennas were not fully appreciated by me, a few of Cecils' helpful insights and encouragement and I built one and was rather surprised ... I do not have one right now but that is only due to neighbors/property constraints. Here is a URL for design/implementation of "non-standard" baluns/transformers, but of a highly useable and desirable nature--or, Dr. Sevick strikes again!: http://www.highfrequencyelectronics....104_Sevick.pdf Fig. 6(A) is very interesting. A 5-winding, 1:1.56 bootstrap transformer which provides 50/75 ohm connections/substitutions. Perfect for allowing one to use 75 ohm "junk" (or found in dumpsters) tv coax in place of more expensive 50 ohm coax. I have made good use of this since I have thousands of feet of NEW 75 ohm coax I purchased from a scrap dealer for next-to-nothing! A lot of large dia coax and hard-line mixed in! Regards, JS |
#3
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Here is a URL for design/implementation of "non-standard"
baluns/transformers, but of a highly useable and desirable nature--or, Dr. Sevick strikes again!: http://www.highfrequencyelectronics....104_Sevick.pdf Fig. 6(A) is very interesting. A 5-winding, 1:1.56 bootstrap transformer which provides 50/75 ohm connections/substitutions. Perfect for allowing one to use 75 ohm "junk" (or found in dumpsters) tv coax in place of more expensive 50 ohm coax. I have made good use of this since I have thousands of feet of NEW 75 ohm coax I purchased from a scrap dealer for next-to-nothing! A lot of large dia coax and hard-line mixed in! Regards, JS A little mismatch isn't such a problem. At least if you can get the loss down. I wouldn't even worry about it, the internal tuner would make short work of that. Look out for water damage on that stuff though. Especially the Aluminum braid/foil shield stuff like LMR. Even a little bit of moisture percolates all through the braid.and turns it into aluminum oxide powder and extremely noisy with power on it. It could look brand new and you would keep cutting it back, then find a foot of new braid but keep cutting and its back to chalk. We would routinely assume it bad and throw it away. At least with the Hardline, you can sweep it and put some power to it to check the loss Only hardline allowed on towers. |
#4
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JB wrote:
... A little mismatch isn't such a problem. At least if you can get the loss down. I wouldn't even worry about it, the internal tuner would make short work of that. Look out for water damage on that stuff though. Especially the Aluminum braid/foil shield stuff like LMR. Even a little bit of moisture percolates all through the braid.and turns it into aluminum oxide powder and extremely noisy with power on it. It could look brand new and you would keep cutting it back, then find a foot of new braid but keep cutting and its back to chalk. We would routinely assume it bad and throw it away. At least with the Hardline, you can sweep it and put some power to it to check the loss Only hardline allowed on towers. Since it was on spools, and dusty, had no concern with that. LOL Regards, JS -- It is like a nightmare where the public servants are people which the police are supposed to protect you from! |
#5
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In message , John Smith
writes JB wrote: ... There ya go. One of the problems of breaking up the path to ground on the shield is that now static can build up. If you can provide a way to bleed off the charges that build up on both halves, while breaking up the shield currents, now you have made it worthwhile. But when you guys start discussing off center fed dipoles, I step aside. I have computers in the shack. I have better luck with fan dipoles. Also running a Butternut vertical. Works a lot better than a 4btv, but a pain to get it right on all bands. Thanks Also liked the other pdfs presented. I never have time to read them all because of constant interruption around here. Back to work. OCF antennas were not fully appreciated by me, a few of Cecils' helpful insights and encouragement and I built one and was rather surprised ... I do not have one right now but that is only due to neighbors/property constraints. Here is a URL for design/implementation of "non-standard" baluns/transformers, but of a highly useable and desirable nature--or, Dr. Sevick strikes again!: http://www.highfrequencyelectronics....104_Sevick.pdf Fig. 6(A) is very interesting. A 5-winding, 1:1.56 bootstrap transformer which provides 50/75 ohm connections/substitutions. Perfect for allowing one to use 75 ohm "junk" (or found in dumpsters) tv coax in place of more expensive 50 ohm coax. I have made good use of this since I have thousands of feet of NEW 75 ohm coax I purchased from a scrap dealer for next-to-nothing! A lot of large dia coax and hard-line mixed in! Regards, JS What about the loss in the balun? You need to decide if the loss in the balun is less than that you would get if you simply used the 75 ohm coax direct. And ask yourself 'In my application, why would 75 ohm be more lossy?' Also, with similar physical dimensions, construction etc, 75 ohm coax is slightly less lossy than 50 ohm (current is less, so 'I squared R' loss is less). -- Ian |
#6
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Ian Jackson wrote:
... What about the loss in the balun? You need to decide if the loss in the balun is less than that you would get if you simply used the 75 ohm coax direct. And ask yourself 'In my application, why would 75 ohm be more lossy?' Also, with similar physical dimensions, construction etc, 75 ohm coax is slightly less lossy than 50 ohm (current is less, so 'I squared R' loss is less). Simple solution, I trust my S-meter! Regards, JS -- It is like a nightmare where the public servants are the people which the police are supposed to protect us from! |