On Sun, 2009-02-01 at 16:31 -0500, Bob Close wrote:
> Drilling through a window--wow, you are a pretty confident person! I took a
> different approach, where I drilled two 5/8 holes through the side of the
> house at the same approximate spacing being careful not to grab the
> insulation. I carefully pushed two 1/2 plastic conduit through the holes,
> and cut them flush with the inside and outside walls, caulking them
> carefully. Inside and outside, I mounted a couple of porcelain insulators
> designed to pass a wire through a chassis. I ran a piece of 12 AWG solid
> copper wire through the conduits to join the outside insulators to the
> inside. I know that there are probably some impedance bumps, but that is a
> problem in theory only at HF frequencies. At 2KW there is no warming at
> all, I am well insulated from any wooden structure, and outside I have a
> little piece of siding to act as a "roof" to keep the terminals dry. I
> connect the window line to the insulators using a gadget I made up out of a
> couple of dual banana plugs/jacks. When not using the antenna I pull the
> connection off and plug the banana plug into a well-grounded copper plate
> with holes the appropriate size and distance. Clean, fast and it's worked
> just fine for ten years. I had the ladder line vaporized by a direct
> lightning strike while grounded with no damage to any inside equipment.
> amazing and/or lucky!
> K1SRR
> Bob
>
Since you are tuning the balanced line, the impedance bump isn't even a
theoretical problem, you just tune for the match and don't care what the
feedline did. In the life of my long centerfed wire, I used 300 ohm flat
TV line, 1" space 18 gauge copperweld, and Ma Bell direct burial phone
wire with a spiral bronze shield. They all tuned, they all worked. The
300 ohm flat had too great an air foil for the strength of the
conductors. The direct burial wire was blown up with a lightning strike
and I didn't have enough left over to put it back up again. The 18 gauge
copper weld stood up to wind the best but when ice coated and flexed, it
broke too.
73, Jerry, K0CQ
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