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![]() David wrote: Try it with a true balanced input. ++++++++++++++++++++++++Ihave. I used a home made 1:1 torroid tranformer with minitmal effects. I even tried it with a 1:1 balun at the far end, with no effect. The only point I am trying to make is that the twisted pair and paralled conductor that I tried were not completly balanced. Perhaps high quality CAT6 ethernet cable would be. We are moving into the realm of "how many angels can dance on the head of pin". Interesting from a philosphical point of view, but not much use in the real world. I have been trying to find better ways to reduce noise since before I got my EE. In my experience better reception, IE receiving the really weak signals, has more to do with reducing the QRM and QRN then "magic" feedlines. I am not in love with coax, it is just the easiest/best solution to keep my feedline from picking up noise, and with common mode supression, keeping noise from finding it's way back up the shield and getting into the antenna. As I have said, if I lived in the woods, with no electrical equipment to be sources of RF noise, then the type feedline I used would not matter. BTDT But in the world that I live in, there are a variety of noise sources in my house that I have mitigated as far as possible. One step in mitigation was to reduce QRM ingress as much as possible. With one, or more, PCs, AC to DC power supplies, DSP(rather noisy) and other noise sources in my shack, coupled with the other household equipment, "smart furnace" fridge, wifes PC, TV/VCR/DVD, microwave, alram clock, and every light switch, I found that I could not get a balanced RF feed to work. However the audio that I distribute around our home is balanced for the reasons you listed. At work we distribute some video via balanced tiwn-ax up to 2 miles. We are replacing these with fiber not because balanced doesn't work very well, but because lighting strikes keep frying the line drivers. In a situaiton where one was using a balanced antenna,like a dipole, with no significant local noise sources parallel, twisted or orpen ladder line would be great. For extremely high power transmit operations open ladder line is the best choice. But there will more leakage from the open line then from coax. Terry |
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