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Author Topic: power lines  (Read 4193 times)
KF6DBZ
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Posts: 28




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« on: July 10, 2012, 09:57:46 AM »

Hello, I want to put my Arrow 2 meter J pole on the garage roof to use my Icom 706. The problem is there are power lines in the alley behind my garage. The antenna will be about 20 feet in the air and about 20 feet from the wires, Is this too close to be safe? I want to put a 10 meter ringo up in the furture is this too close for that antenna? i am worried about arcing from the wires.

Thank you for your input.

KF6DBZ
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KC9NVP
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« Reply #1 on: July 10, 2012, 10:19:20 AM »

You need to find someplace else to put the antenna!!!!!!  Cheek the ARRL handbook for information setting up an antenna.  If I remember correctly, you should be at a minimum of 1.5 x the height of you antenna from any power lines.  2X the height distance would be better, if the wind get hold of the antenna and blows it over onto the wire, you will find your self in a world of hurt and maybe 6 - 8 feet under ground.
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KF6DBZ
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« Reply #2 on: July 10, 2012, 10:25:58 AM »

The high power lines are atleast 40 feet in the air, if the antenna were to blow ove there is no way it would reach the wires. i think it will be ok, just wanted to see what other people think. Thank you for your input.
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W9GB
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« Reply #3 on: July 10, 2012, 07:24:55 PM »

Quote
I think it will be OK, just wanted to see what other people think.
Thank you for your input.
SEEK Local Assistance -- When you don't know what you are doing.  We don't have a video feed to perform remote assessments.  It requires your Common Sense and ability to foresee "What If".

1. Last year, it was well publicized that 2 amateurs lost their lives installing antennas, that fell on or touched AC power distribution lines.
2.  The antenna and tower manufacturers have posted stickers on their products and instructions about proper installation since late 1970s.  These were industry changes after numerous accidents and lawsuits in 1970s (CB craze), where a family member died and the surviving relatives sued everybody.  Remember the McDonalds' hot coffee lawsuit?
3.  Best advice is to keep antennas as far away as possible for commercial AC power lines and overhead service entrances.

w9gb
« Last Edit: July 10, 2012, 07:26:56 PM by W9GB » Logged
KC4MOP
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Posts: 754




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« Reply #4 on: July 11, 2012, 03:54:53 AM »

I know you already realize the safety factor. It's a little too close for my comfort, but electrical noise will be closer to your antenna and may cause an S-9 or more of noise. You will never hear someone that is below that noise.

Fred
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K1CJS
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« Reply #5 on: July 11, 2012, 04:56:14 AM »

It could well be that you should find another location for the antenna, but if that location is the only one you can use, try it--making sure that the antenna will not touch the power lines if it should fall.  IOW, mount it a little closer to the garage roof.  Make sure the mounting method is a secure one so a windstorm will not cause any problems such as the antenna being blown into the wires, and you should be OK.  Noise won't be a problem on FM, but may be on AM or SSB work.
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WX7G
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« Reply #6 on: July 11, 2012, 06:09:38 AM »

As you say your antenna will not contact the HV lines if it falls. There is no problem.
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KG4NEL
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« Reply #7 on: July 11, 2012, 06:34:34 AM »

Sounds like the building is in the fall zone of the lines, anyway?

That would probably give me pause, antenna or not Smiley
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KI4SDY
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« Reply #8 on: July 11, 2012, 07:44:26 AM »

Never install an antenna in close proximity to power lines (the same side of the house). That is just common sense and part of knowledge that is required for ham licensing. Wink

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KL3HY
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Posts: 120




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« Reply #9 on: July 11, 2012, 10:18:29 AM »

As you say your antenna will not contact the HV lines if it falls. There is no problem.

I don't see how you can make that determination.  Every year we have trees falling on distribution lines, knocking them down in some cases.  Granted, his location of Torrence, California is very different than mine here in Anchorage, Alaska.  What happens if some drunk driver slams a big SUV at high speed into one of the power poles, knocking it down onto his antenna wire?

I agree that it would probably be a very unusual set of circumstances that would result in the worst-case scenario, but we take safety precautions based on dangerous potential events, not common benign ones.
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LA9XSA
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« Reply #10 on: July 11, 2012, 11:39:28 AM »

One way of looking at this is that your garage is already near the power lines, and it's probably connected to your house by low voltage lines - if the power lines fall down your antenna might not make much difference in the damage caused to your house and garage.

However, I would not put the antenna on that side of the house. High voltage power lines have an electric and magnetic field around them, and I'd personally consult a qualified engineer before putting up antennas, or anything metallic, under a high voltage line.
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K0ZN
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« Reply #11 on: July 11, 2012, 09:03:54 PM »

If you are ABSOLUTELY sure there is plenty of EXTRA distance for the antenna to fall, be blown over, etc. then you are OK.  Again, as a previous
post said, we don't have video of the installation, so responses are educated GUESSES.

The other question to ask is: What happens if the power line breaks and comes down?  Are you comfortable with that?

Fully understand that your antenna does not have to touch the line.... the voltage is high enough that the current WILL ARC.... up to several FEET if you get too
close.  THAT is one of the reasons you need "extra" distance.

If you do put it up, I would strongly recommend you put a LARGE, such as #4 gauge wire, securely fastened to the mast, to a KNOWN Earth ground, like a ground rod you install. Make sure your coax shield is grounded to the mast and safety ground too.

This hobby is a lot of fun, but it sure is not worth dying over !  We had TWO hams killed here a couple of years ago when the antenna they were installing hit a
7,200 volt line....apparently, they slipped on the roof or something and the antenna went into the line.

Ham radio is a hobby and sometimes compromises, such as putting an antenna is a less than desirable place kind of "has" to happen....but, risking death to
talk on radio doesn't make sense.

73,  K0ZN
« Last Edit: July 11, 2012, 09:06:18 PM by K0ZN » Logged
KQ6Q
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Posts: 991




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« Reply #12 on: July 11, 2012, 09:41:11 PM »

KF6DBZ - you're in Torrance, with lots of hams around - up on PV, at TRW, etc. Get on one of the local repeaters with an HT, and ask for someone to come by and advise you, where they can see the actual situation, and make a solid recommendation. 
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WX7G
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« Reply #13 on: July 12, 2012, 05:16:58 AM »


Fully understand that your antenna does not have to touch the line.... the voltage is high enough that the current WILL ARC.... up to several FEET if you get too
close.  THAT is one of the reasons you need "extra" distance.


Power lines in an alley will be 2100 V lines. The peak voltage is 3 kV and that will arc 1/20 of an inch. With field enhancement due to sharp edges it might arc 1/10 of an inch. The dielectric strength of air is 70 kV/inch. Once an arc is struck the electrodes can be pulled apart and the arc will continue to quite a distance.

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KF6DBZ
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Posts: 28




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« Reply #14 on: July 12, 2012, 09:48:59 PM »

I put up the antenna all is good. No interference or anything like that. If i had a direct line from the antenna to the power lines id would be at least 30-40 feet. I felt the mounting was safe i just wanted to see what everybody said. Thnak you for your comments and concerns.
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