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Author Topic: 2nd Floor Shack But Feedlines in Basement!  (Read 1158 times)
AA9ZY
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Posts: 9




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« on: March 23, 2003, 05:22:06 PM »

I recently got permission from the xyl to relocate my shack to a spare bedroom on the 2nd floor our house. Unfortunately, the antennas and rotator cable come in the house through the basement.

I could run the cables in through the bedroom window, but wouldn't that create more risk for damage from lightning? I'm using Alpha-Delta transi-traps with an outside ground rod and have a roof tripod grounded to the same ground rod.

So far, none of the local hams have been able to solve this problem for me. I really don't want to run long runs of RG-213 upstairs next to the hot air ductwork if I don't have to, but what can I do? Relocate back to the basement?

73's,

AA9Zy
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WB2WIK
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Posts: 20540




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« Reply #1 on: March 24, 2003, 05:52:57 PM »

It doesn't make much sense to run lines from the roof to the basement and then back to the second floor.

I'd tear out the existing lines running to the basement and figure a way to re-route them to the 2nd story bedroom (or possibly replace them altogether with new lines if they're aging, anyway).  Opting for bringing such cables in through a window is something I never do, if for no other reason than it's tacky and looks lousy.

You can always bring the cables from the roof into the attic or crawlspace, and then down through the ceiling in a nearby closet, so the cables are completely hidden except where they exit the closet and route to your station equipment in the upstairs bedroom shack.  That's very nice and neat, and is bound to reduce the cable lengths required.

As for grounding, if it's lightning protection you're concerned with: You need to provide a lightning ground which is OUTDOORS and in no way connected to your station equipment, and this ground should be lower impedance than your coaxial cabling and rotor cabling.  If the ground conductor from your antenna to earth ground (the lightning ground, which should never enter the home) is made of 6" wide copper flashing and your coaxial and rotor cabling combined is about 1" diameter copper, and both lengths are about the same, you'll have accomplished your goal.

You never want your coax/rotor cables to be the lower impedance path to earth.

WB2WIK/6
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AA9ZY
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Posts: 9




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« Reply #2 on: March 24, 2003, 07:24:45 PM »

Sounds like an interesting idea with running the feedlines in under the eave, into my crawlspace. I've seen other hams do that, but it always looked unsafe.

If I understood you correctly, you're recommending that I place my lightning protection up at my roof? I currently have my roof tripod grounded, so that would be a convenient location for protecting the rotator and coax from my vhf antennas, but not practical for my Carolina Windom, or for the inverted-L antenna I'm planning for 75 mtrs.

73's,

AA9ZY
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WB2WIK
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Posts: 20540




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« Reply #3 on: March 25, 2003, 11:26:27 AM »

The lightning ground should be a large, broad conductor attached to your roof tripod and routed directly to earth using a path that is shorter and lower impedance than your feedlines and rotor cables.

For example: Use copper flashing or very large conductor (#0 copper is pretty good) clamped to the tripod, and run directly to earthing via the shortest possible path, and that path should never be through the house.  Let's say that path is 35 feet long.  Great.

Now, make your feedlines and rotor cables substantially longer than that 35 feet, and run them inside to the station.

Obviously, there's lots to know about grounding for lightning protection.  There was a multi-part article in QST last year on this very subject, and much information is available from the Polyphaser website.

Since you cannot directly ground a wire radiator, normal protection is employed in the antenna feedline and again should be outside the house, never inside.

If a huge slug of current is conducted to earth via the feedline, the feedline might simply fuse (melt) and open that circuit, but it will have done its job by then.  You want that big current surge to all flow from your antenna to earth, leaving the balance of feedline going to your station equipment as a high impedance path which won't conduct any of the surge.

WB2WIK/6
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