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Author Topic: lightning-arrestor for transmission-line  (Read 2186 times)
KM3K
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« on: April 08, 2009, 06:34:38 PM »

I'm certain I have seen advertised lightning-arrestors for transmission-lines but my searches tonight have come up empty.
My hope is that:
1. I could mount the arrestor near the peak of my attic (about 25' high),
2. that it is capable of passing the signal to the inside of my attic where the line would run to my SGC-237 antenna-coupler (also in the attic).
3. back at the outside of the building, I'd also run a #4 or #6 wire from the arrestor to a suitably installed ground-rod.
Thanks for any assistance.
Jerry, KM3K
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KM3K
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« Reply #1 on: April 08, 2009, 10:57:12 PM »

The answer is ICE.
The arrestor needs to be mounted at ground-level.
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K9KJM
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« Reply #2 on: April 09, 2009, 01:04:03 AM »

I also feel that I.C.E. (Industrial Communications Engineers) has one of the better deals on arrestors.

However, Be aware that the actual device used is about near the bottom of the list in importance of things to do for lightning protection!  MUCH more important is proper bonding, etc.

For some good information about lightning protection:


http://members.cox.net/pc-usa/station/ground0.htm

For some tips on how to do it on a budget pick up a copy of the May 2009 Popular Communications magazine.

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KB9CRY
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« Reply #3 on: April 09, 2009, 05:21:27 AM »

back at the outside of the building, I'd also run a #4 or #6 wire from the arrestor to a suitably installed ground-rod.


You run your feedline down from your antenna to the ground where you install the arrestor and your ground rod.  Then you route your feedline into the house and to the rig.
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AA4PB
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« Reply #4 on: April 09, 2009, 05:46:18 AM »

You have to be careful about putting arrestors on the antenna feed from an SGC tuner. If you are end-feeding a random wire antenna then you can have some very high voltages on the feed line, even with only 100W and most arrestors are NOT designed to handle such high voltages. Even the ICE balanced feed arrestors are only specified for a 300-600 ohm impedance and an end-fed wire can be a much higher impedance, which means much higher voltage.

Typically about the best you can do is a home-made arrestor with the gap set wide enough that it never arcs over during normal operation - but that typically means that you can have several thousand volts on the antenna lead in before it arcs over.

Tell us more about your antenna type, installation, lead-in routing and tuner grounding and someone may be able to come up with some more suitable suggestions.
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KM3K
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« Reply #5 on: April 09, 2009, 04:27:09 PM »

First off, I fully comprehend the overall grounding principles; I've been to the suggested sites.

As requested, coming back with some details/numbers:
1. Two-story house is 27' high.
2. a ten' high 1.5" diam electrical-conduit will add to that a little bit more height.
3. a brick-chimney is some 3' away; use to support wires coming down from the antenna.
4. have 50' Bury-Flex coax.
5. the shack is in the basement; Yaesu FT-950.

Two antenna possibilities; I have these antennas and eventually would have both installed:
1st choice due to easiest install....a PAR EF-20 end-fed wire antenna that is coax fed.
Usable only on 20-meters.
Coax would run to ground-level into a ICE lightning-arrestor and then into the house.
2nd installation....a 40-meter TAK-tenna, which can be used on other bands when a transmission-line feed is used.
A coax, as I understand it, permits only 40-meter work.
A ham gave me 450-ohm ladder-line as a gift.
I imagine running the ladder-line down the side of a brick-chimney to the ground where a lightning-arrestor would be located.

I assume I will find a suitable weather-proof container ala the pictures at vk4zxx web-site for the lightning-arrestors and my SGC-237 antenna-coupler, which would allow for coax entry into the basement area.
What have I left out??
In all the research I've done, the one thing that amazes me is the ham community seems to stress putting the arrestors outside the shack, yet pictures for the commercial community have them on the inside.
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KB3RHV
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« Reply #6 on: April 09, 2009, 11:24:47 PM »

I would mount a NEMA enclosure at the bottom of your chimney and run gray PVC pipe or ceramic pass through spacers out and up from it for a inverted L antenna.

Put the SCG tuner in the NEMA box and run a ground out from it to two ground rods spaced four feet from each other.

Now you will have a multi-band antenna that is simple and easy on the eye.

NEMA box: http://www.l-com.com/productfamily.aspx?id=6015

Lcom is pricey, so I would also look at Lowe's and Home Depot, they carry them as well.

Also, if you get the box big enough, you could put the arrestor in there as well. I would also get arrestor for the DC power cable connections as well. Since you will need to run 13V to the SCG tuner.

For running the coax and power, you can just bury them both to a basement window that has a plywood panel for the cables to pass through.
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K9KJM
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« Reply #7 on: April 10, 2009, 12:46:36 AM »

Quote: "In all the research I've done, the one thing that amazes me is the ham community seems to stress putting the arrestors outside the shack, yet pictures for the commercial community have them on the inside. "

That seems to be mostly because many "hams" are still several years behind truly effective commercial installation procedures.

As you point out, Really "mission critical" communications systems that cannot be allowed to fail, Like police, Fire, Ambulance, etc that are installed to todays standards have the arrestors INDOORS.

ALL of my own arrestors and coax switches are INDOORS.

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AA4PB
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« Reply #8 on: April 10, 2009, 05:08:18 AM »

Inside/outside doesn't matter. What matters is that you want a reasonably short run of heavy guage (#6 minimum) conductor between the arrestor and ground. You don't want to run the coaxes half way across the building to the arrestor and then a ground wire half way across the building back outside to the ground. Mounding the arrestor on the inside of an outside wall should be fine.
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KB9CRY
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« Reply #9 on: April 10, 2009, 05:38:12 AM »

You can mount them indoors but you will need a very low impedance bonding from the indoor mounting panel to the SPG outside.  Most commercial stations I have seen use wide copper strips.
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KM3K
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« Reply #10 on: April 10, 2009, 08:57:47 AM »

About an inverted-L antenna, I never considered it but will "put it into the mix".
Now my reading of that posting is the antenna would start at the NEMA-box; did I get that part right? If not, please explain what I should do.
Also, not that I can do anything about it other than move, I'm on a corner-lot and have 3-phase high-voltage lines running the length of my property; they are some 20' away from whatever I put up (no danger of accidental contact unless there is a catastrophic earthquake causing those lines to fall on my house).
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KB3RHV
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« Reply #11 on: April 10, 2009, 11:53:21 AM »

Yes, it starts from the side of the nema box. We used one of these from ware the wire comes out and up to seal it and hold it from pulling out.

PVC Strain Relief Connectors: http://www.farmtek.com/farm/supplies/prod1;ft1_electrical_supplies-ft1_plugs_connectors;pglj2400.html

We also used gray pvc pipe that T off so many feet to keep the wire away from his tilt tower that he built. So it kind of looked like this, but with a SCG at the bottom.

http://www.bloomington.in.us/~wh2t/invertedl.html

End insulators we used:
http://www.universal-radio.com/catalog/antsup/4763.html

The wire we used was 14GA of Flex wire from Lowe's. It was 40$ for a 500Ft spool and its jacketed.

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KM3K
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Posts: 299




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« Reply #12 on: April 10, 2009, 02:12:41 PM »

Thank you for the posting.
1. Would you consider this a difficulty?
A few years back, I had a new gas furnace installed; because it is a higher efficiency model, the chimney needed a stainless-steel flexible liner installed and that liner runs the length of the chimney (probably some 30'). Now I did not pay any attention to how the workers connected it to the inside-the-house furnace-piping, so I don't know if it is grounded. A phone-call to the gas-company on Monday could answer that. Lets say for now that it is grounded, in which case it would be no different than the tower shown in the link you sent me. Do you see it that way too?
2. Concerning ground-radials, is bare-wire preferred and what gauge would you suggest?
73
Jerry, KM3K
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KB3RHV
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« Reply #13 on: April 10, 2009, 02:32:26 PM »

For grounding, run a wire from the SCG's ground lug to the Metal plate in the nema box.

From there, run 2 NO 6 ground wires from the box's plate and out of the bottom of the box to 2 ground rods spaced 4ft apart.

This will give you the grounding you need for the ICE arrestors and also the ground you need for the SCG to make the L work.

It basically the same we did for my buddy's setup.

The only thing you will need to do, is mount a bracket to the side or top of the chimney for the wire support.
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AA4PB
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« Reply #14 on: April 10, 2009, 03:17:09 PM »

Remember, the NEC requires you to tie the antenna ground sytem to the home's electrical ground system.

I also question whether two ground rods is a sufficient RF ground for an end-fed antenna like an inverted-L. You may get by with it if the L is 1/2 wavelength long but not on bands where the L is some other length.
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