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Author Topic: For all the antenna guru's  (Read 931 times)
W9FFC
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Posts: 32




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« on: January 09, 2011, 05:37:56 PM »

I have a 18,000 high voltage line in my back yard even with the roof of my 2 story house, and 50' away running in a North South direction.
My question is: in what direction should I run my 80/40 trapped dipole to avoid picking up the least amount of noise from the power line.

73.............Bob
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AI7RR
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Posts: 164




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« Reply #1 on: January 10, 2011, 11:49:32 AM »

Your best option is probably going to be perpendicular to the noise source and obviously as far away as possible. There is also the possibility of increased static charge, so I'd make sure to include some form of a discharge device.

73,,Roger
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NO6L
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Posts: 179




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« Reply #2 on: January 10, 2011, 12:55:01 PM »

There is no short answer. Is it really coming from that line? If the line is the source, nothing you do with that antenna will be of much help. You will have to notify the electric company. Give it a couple of times to a couple of different levels of their management. If you still don't get satisfaction you'll have to call in some help via the FCC. Don't expect "Next day service", but you will get results eventually. They usually don't take kindly to interference to their territory. Read further though, because some types of noise can sound like pulse, or power line noise.

The first thing to do is confirm how the noise is arriving, the mode. When it is there, disconnect the antenna/s and see if that has an affect. If not, it's arriving through other means or is internal. Internal noise can be intermittent and sound like power distribution line noise. Next, unplug all external devices, including the mic to see if there's an effect. If you can, run the rig on a battery or sub in one that can. And don't jostle the rig at all, if it's internal you may temporarily "fix" it. To be sure, leave it on while investigating.

If you've confirmed it's coming from outside, use the attenuator and/or RF gain to get the noise down to zero. Then bring it back up until you begin to hear it. The reason is, there can be more than one type/source of noise, but it's unlikely they'll be exactly the same level. Turn on the noise blanker to see if that has an affect. Yes? It's pulse noise. That may or may not be the distribution lines. Some types of pulse noise is not affected by the noise blanker. If it doesn't, it may be RF based and that can sound like pulse noise but the noise blanker won't affect it. Dial your VFO and if it comes and goes about every 15 - 200 Khz it's a switching power supply. If not, it's probably pulse noise that the blanker can't handle. Using sensitivity to single out noise is the best way to proceed, because you're getting rid of the "worst first", instead of trying to find all sources at once, which never works. Now, use a portable type of non-FM receiver with an RF gain and hunt down each source.

If it's a switching supply, you have to narrow it to where it's coming from. If it's really strong, it may be from your own residence. Run your rig on a battery or sub one in that can, and kill all power to your house. Is it gone? Yes? Good news, easy fix, power up each circuit, one at a time, there may be more than one source, to find out which branch it's on. If it's coming from outside, you've got a potentially sticky situation. Remember, "He who purchases an item, has purchased perfection". And no matter how much in the right you are, you're wrong. Now if that "perfection" is interfered with, you are wrong then, too. This is neighborhood politics at its best. If the suspected power supply is in a friends house, the job just got easier by magnitudes. If not, you have to decide; do you get the FCC involved and end up with a really angry neighbor, or "Just muddle through"? That depends on your situation and there's nothing I or anyone can do to help. As for me, I have to muddle through, I know where all the switching supply noises are coming from, and due to my living situation, there's nothing I can do but accept it.

73
NO6L
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WB2WIK
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Posts: 20542




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« Reply #3 on: January 10, 2011, 02:18:29 PM »

You have an 18kV line that's only as high as the roof of your house?

I've never seen one that low -- or maybe you have an extremely tall house. Cheesy

Around here all HT lines (usually 7200V or 14.4 kV) are at least 50' above ground, most are higher than that.  Trees still grow up into the lines and the DWP has to come trim the trees when that happens; but if they were lower, it would happen all the time and really drive them nuts.

Whichever way you run your wire antenna, don't run it so it could come closer than several feet away from such a line, use really good end insulators and support rope, and arrange it so if it breaks, even in a windstorm, it still couldn't come close to the HT line.
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KH6DC
Member

Posts: 634




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« Reply #4 on: January 11, 2011, 11:34:22 PM »

My guess is you're at the top of a hill and the powerlines are on a pole but in a depression such as a valley, hence the 18KV line right up to you're roofline?  I agree, run your dipole perpendicular to the powerline and as far as possible since it could arc due to static discharge.  The dipole itself will pick up less noise than a vertical.  You could also think of the powerlines as a large dipole sending signals your way.
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73 and Aloha,
de Delwyn, KH6DC
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