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Author Topic: 12 meter noise  (Read 1033 times)
N3VMC
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« on: July 06, 2008, 12:17:56 PM »

Ugh.....this is really annoying to say the least.

Yesterday I installed a good 1:1 iso balun at the feedpoint of my R5 to eliminitate the stray RF in my shack. Last night the RFI on 12 was so bad I turned the rig of.....now...today 12 and 20 are nasty.

Earlier today I shut off the main breaker and powered my ICOM with the 12v setup I use for camping. The noise was still there at 20+db. So I took an AM radio around the house....thinking I might find something.

Unfortunately I did....and its a nasty signal. I found a good EMR source behind my entertainment center.....about 4 feet off the floor. The only thing in that are is some 75 ohm coax running up the wall into my master bedroom and a phone line for the Tivo.

With the power off the RFI is screaming up and down the 75 ohm coax....but when I checked in the basement where the coax came in....there is nothing.

I havent talked to me neighbor on what might be on the other side of that wall....but then again how do I know whatever is over there is causing the interference in the first place?

Before I put this R5 up I had an Alpha Delta DX-EE that worked pretty well running above the roof at about 10 feet. I never had any RFI issues with it....and up until a few days ago....before I installed the balun...I didnt have any issues with the R5. Could the balun be contributing to this problem?

I made a short video of my ICOM display with audio of the signal. You can see it very clearly on 12 and a little bit on 20.

Any ideas?

here is the link to the vid...its about 45 seconds long.

http://www.flickr.com/photos/cerberus314/2642829418/

73
Vince
N3VMC


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KB9CRY
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« Reply #1 on: July 07, 2008, 07:47:17 AM »

The R5 doesn't need a balun; it has it's own matching section in the black box at the base.
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N3VMC
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« Reply #2 on: July 09, 2008, 12:31:55 PM »

"The R5 doesn't need a balun; it has it's own matching section in the black box at the base."

Thats not the point but thanks for your 2 cents. I know it has an choke balun and a 4:1 balun but that dosent stop RF from coming off the feeline....thats why I added the other one at the feedpoint.

The choke balun on the R5 dosent isolate jack.
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W1AEX
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« Reply #3 on: July 10, 2008, 09:08:20 PM »

Hi Vince,

Had any thunder/lightning storms lately? That noise sounds like a blown lightning arrestor on a powerline. The noise that is generated can travel quite some distance. Your display looks exactly like mine did on my 756 Pro III. Take a listen to this and see if sounds familiar to you:

http://members.cox.net/w1aex/w1aex.mp3

It was cleaning me out from 160 - 40 meters, and I could hear it as high as 6 meters. I got my local power company to come out and they found it after searching for 3 days, in another town, over 3/4 of a mile away, deep in the woods on a 26KV line that feeds my neighborhood. I was glad to see it fixed!

Rob W1AEX
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N4UE
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Posts: 297




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« Reply #4 on: July 24, 2008, 05:39:46 PM »

Vince, I feel your pain. Another local ham and I have had the same problem. Yes, it's Powerline noise!. I have a 756PRO and my display is was EXACTLY the same as yours. I made a couple of Kent Brittan's "cheap yagis" and went searching with my Icom R10 receiver. Since the yagis are made with thin welding rod and 3/4" PVC, they weigh next to nothing. I made a 3 element one for 136 mHz and a 9 element one for 435 mHz. The 136 will get you in the right direction and the 435 one is sharp enough to point right to the top of the pole and at a bad lightning arrestor.
Florida Power and Light are just wonderful people. They will go waaaay beyond the normal Utility Company response. They just LOVE it when I identify the pole and put an orange ribbon on it, so the crew doesn't have to screw around 'looking' for the problem.
Don't get me wrong, FPL has all the state-of-the-art gear, but if I can save them a day or two of looking, they really appreciate it.
The ARRL has a great book on 'noise'. I regretfully say I have learned a LOT more than I ever wanted to on the subject of Powerline noise, but you gotta keep working at it.
Oh, I am the last person on my distribution line. Unfortunatly, we have had some wicked lightning storms here lately, so it's just patch, patch, patch.

Don't dispair! It CAN be fixed!!!

Contact me off the list if you need advise....

73

ron

n4ue@arrl.net
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