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On Wed, 02 Mar 2005 13:04:50 -0500, clvrmnky
wrote: I know that receivers are less demanding of impedance matching in general, but my readings suggest that I should have a balun (unun) of some sort to match the impedance better, since I'm pretty much stuck with end-fed longwires. Hi OM, This match, as you speak of, is probably remote from any probability you are likely to encounter with the antenna options you describe in your posting. However, there are other merits: a proper shielded connection to my receiver should help minimize stray RF noise. Presuming you mean to terminate the far end shield connection to ground. I'm guessing the real advantage would be realized if I had a good RF ground at the receiver and/or balun. This will be sort of tricky. I don't even think I have copper cold-water pipes anywhere, and running copper braid over the balcony, down the side of the building and into 6-foot rod just ain't going to happen. OK, so we strike out those as options not available to you. I've heard of people using houseplants for poor grounds when no other was available, and I have many kilos of wet earth on the balcony. Don't even think of it. Ground does not mean wet mud. I've seen a neat artificial ground/antenna tuner from MFJ (I think) which seems to offer a lot of bang for the buck. It even has multiple inputs for high-Z single wires. Would this be useful for SW? Certainly, but you would achieve just as much with a simple tuner (cheap one without the transmitter meters). In fact, this tuner is generally very necessary to keep local AM stations from desensitizing your receiver. This is a common plight suffered by many who would otherwise think they were doing pretty well, but just need more antenna to get those signals others are reporting. Finally, I'm probably just going to wind my own balun out of a ferrite core. I just can't seem to find the details on how to wind the copper. Do I wind the primary first around the whole core, and then the secondary on top of it? What you are describing is a conventional power transformer - NOT the same thing as a Transmission Line Transformer. What you should really concentrate on is what is called a Transmission Line Choke (perfectly accomplished using a 1:1 Current BalUn/UnUn). 73's Richard Clark, KB7QHC |
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