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Author Topic: Shack entry safety/grounding for open wire feedline?  (Read 1103 times)
W9XC
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Posts: 17




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« on: August 07, 2012, 02:03:20 PM »

The best-practice approach for feedline entry to the house/shack seems be a single outside entry point for all wire, at a grounded outside panel that has lightning protection devices and direct connection to the main house exterior ground rod/grounding system. That is, ground everything at a single common point before entering the building.

Most of the discussion about this approach references coax feedlines, and recommends grounding the coax shield at this panel, which is pretty clear how to do.

What about open-wire feedlines, that have no shield to be grounded?  What's the best practice for getting them into the house, lightning-protected?

- Les, W9XC
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LA9XSA
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Posts: 376




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« Reply #1 on: August 07, 2012, 06:56:05 PM »

Earlier thread:
http://www.eham.net/ehamforum/smf/index.php?topic=75231.0

See also Lightning Protection for the Amateur Radio Station -- Part 2
QST July 2002, pp. 48-52
http://www.arrl.org/files/file/Technology/tis/info/pdf/0207048.pdf

There are commercial protectors available for open wire line, and some homebrew solutions,* but I think I'd choose one of these tactics
- Throw the open wire line out of the house and ground it below the feed point when not in use.
- Put the balanced tuner on the ground outdoors some distance from the house, making for a practical ladder line/OWL run between antenna and tuner. Put open wire line protectors where the ladder line enters the tuner (might be a waste of time). Ground the tuner itself well. Now no ladder line enters your house, just 50 ohm coax and control lines, which you put the same protectors on in your entry box as your other coax and control cables.

I would never want ladder line/OWL to enter the house in a thunderstorm. In the first tactic, a direct strike will turn both the dipole and feed line into a spray of hot copper and plasma. In the second tactic, the same thing will happen and perhaps kill your tuner, but hopefully not kill your house and shack.

If you live in a place with dry vegetation or much lighting, I'd take down the whole antenna whenever not operating.

*: Note that when you tune a balanced feed line across many bands on full power, you could have some pretty high voltages where the ladder line enters the tuner. This could easily surpass the clamping voltage of commercial protectors. Homebrew alternatives include air gaps created by grounded cylinders around each lead of the feed line.
« Last Edit: August 07, 2012, 07:51:15 PM by LA9XSA » Logged
KB4QAA
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Posts: 2382




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« Reply #2 on: August 08, 2012, 12:25:20 AM »

http://www.thewireman.com/prodpix5.html

http://www.thewireman.com/ground.html

Item 878 is an open wire lightening arrester.
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WX7G
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Posts: 6080




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« Reply #3 on: August 08, 2012, 03:27:06 PM »

The Wireman knife switch is an absolute piece of junk. Radio Shack carried them and they don't stay closed.

The Wireman openwire lighting arrestor looks very homemade out of two spark plugs. It might work but looks crude.
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AD5X
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Posts: 1430




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« Reply #4 on: August 08, 2012, 03:47:35 PM »

Here's a knife switch that is inexpensive and available, but I don't know anything about the quality:

www.allelectronics.com/make-a-store/item/SWS-13/D.P.D.T.-KNIFE-SWITCH/1.html

Phil - AD5X

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