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Title: Why is the winding shorted on all of these balun schematics? Post by: Opcom on December 06, 2020, 10:20:36 PM These are the common 75 Ohm coaxial -to - 300 Ohm unbalanced matching devices that are (or were) used with TV sets, FM receivers, and any other purpose.
Just about every schematic of these shows one of the windings to be shorted, that is grounded at both ends. I do not understand why this is good or correct. Anyone know about this mystery? hundreds are shown this way https://www.google.com/search?q=schematic+of+a+75+to+300+Ohm+TV+set+balun&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiX1-3L9LrtAhVEcq0KHcz6C1UQ_AUoAXoECBAQAw&biw=1920&bih=919 Title: Re: Why is the winding shorted on all of these balun schematics? Post by: W1RKW on December 07, 2020, 08:34:06 AM http://www.ham-radio.com/k6sti/balun.htm
Scroll down about 2/3 of the way. you'll see some of the same schematics for 75 to 300 ohm baluns and explanation for the short or no short. Title: Re: Why is the winding shorted on all of these balun schematics? Post by: ka1bwo on December 10, 2020, 03:22:34 PM These are the common 75 Ohm coaxial -to - 300 Ohm unbalanced matching devices that are (or were) used with TV sets, FM receivers, and any other purpose. Pat the schematics are incorrect. Were the transformers are connected in series should not go to groundJust about every schematic of these shows one of the windings to be shorted, that is grounded at both ends. I do not understand why this is good or correct. Anyone know about this mystery? hundreds are shown this way https://www.google.com/search?q=schematic+of+a+75+to+300+Ohm+TV+set+balun&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiX1-3L9LrtAhVEcq0KHcz6C1UQ_AUoAXoECBAQAw&biw=1920&bih=919 Title: Re: Why is the winding shorted on all of these balun schematics? Post by: DMOD on December 10, 2020, 09:06:30 PM These are the common 75 Ohm coaxial -to - 300 Ohm unbalanced matching devices that are (or were) used with TV sets, FM receivers, and any other purpose. Pat the schematics are incorrect. Were the transformers are connected in series should not go to groundJust about every schematic of these shows one of the windings to be shorted, that is grounded at both ends. I do not understand why this is good or correct. Anyone know about this mystery? hundreds are shown this way https://www.google.com/search? q=schematic+of+a+75+to+300+Ohm+TV+set+balun&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiX1-3L9LrtAhVEcq0KHcz6C1UQ_AUoAXoECBAQAw&biw=1920&bih=919 These transformers are based on "Transmission Line Transformer" theory. http://k5tra.net/tech%20library/RF%20transformers/Transmission-Line%20Transformers.pdf http://www.introni.it/pdf/Amidon%20-%20Transmission%20Line%20Transformers%20Handbook.pdf https://highfrequencyelectronics.com/Jan06/HFE0106_TraskPart2.pdf https://www.markimicrowave.com/assets/appnotes/balun_basics_primer.pdf http://www.introni.it/pdf/Amidon%20-%20Transmission%20Line%20Transformers%20Handbook.pdf https://www.amazon.com/Transmission-Line-Transformers-Jerry-Sevick/dp/1884932185 Phil Title: Re: Why is the winding shorted on all of these balun schematics? Post by: Opcom on December 11, 2020, 12:33:47 PM Thank you all, I had not given these little baluns much thought though I had opened many. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
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