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Author Topic: Strong RFI on 20m & 17m - Filters for Major Appliances  (Read 2541 times)
VE6ETP
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Posts: 19




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« on: November 25, 2013, 05:21:44 PM »

On 20m and 17m I have bands of high RFI that completely wipe out signals. I've determined that this is caused by the dryer in my house. Unfortunately due to position needs and where I could actually pass my feed line to the outside, I had to run it right by the 220V power going to my dryer.

But here's the thing, when I unplug the dryer from the wall, the interference drops by about half. However when I pop the breaker for the dryer (and I've confirmed that the dryer is indeed not getting any power), the RFI still exists? I'm a bit baffled by this.

I bought a bunch of different kinds of snap on ferrite chokes as I thought this interference may have been my router or some power adapter from the computer equipment I had running near my rig (I run a Flex 3000). However after unplugging all of these the RFI didn't change. That's when I found the dryer.

So 1, how would I go about eliminating this RFI from the power line to my dryer (aside from moving my feed line). 2, Why does the interference not go away after I pop the breaker? This doesn't seem to make sense.

Let me know if you would like to see any screenshots as I don't think I can attach images to this message.

Also, since writing this the interference has gone down on 20m and increased on 17m. I wonder if the later it gets into the night the more the interference moves up the bands? It's 6:15pm here while I took these pictures.

Thanks for taking the time to read and I appreciate any thoughts on this.

Regards,

Pete
VE6ETP
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WX7G
Member

Posts: 5987




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« Reply #1 on: November 25, 2013, 06:24:53 PM »

The symptoms tell us that the noise is not originating from the clothes dryer.

To see if the noise is originating inside your home the standard test is to power the receiver from a battery and shut off all AC power. If the noise is still present it originates outside your home. If the noise is gone switch circuit breakers on one at a time until the noise appears. Now go to the room(s) powered by that breaker and unplug items until the noise stops.
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KB4QAA
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Posts: 2340




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« Reply #2 on: November 25, 2013, 07:54:06 PM »

Your dryer is haunted. 
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VE6ETP
Member

Posts: 19




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« Reply #3 on: November 25, 2013, 10:29:33 PM »

Ok looks like I identified the issue.

It's the lights in my basement. However just turning the lights off doesn't suffice so it must be the feed into the switches. I assume my feedline must run right beside some lumex.

So this is my own stupidity. I've run my feedline through the drop ceiling and right beside some power lines. Unfortunately I even ran conduit everywhere to make pushing the cabling through easier. Looks like I need to rip it all out. Have to learn somehow I guess.

I assume there's no filtering out household powerlines? Simple solution is to just move the feedline?

Pete
(feeling a little stupid)
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VE6ETP
Member

Posts: 19




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« Reply #4 on: November 26, 2013, 12:25:17 AM »

Just thought I would give an update in case this can help others in the future.

Turns out it wasn't the power line at all. I pulled out my feed line away from the only nearby power line but still had an issue.

I then realized that the breaker also had power to my office 2 floors up. All kinds of computer equipment up there.

In the end it turned out to be a combination of 3 things. One was the hall light, one was a couple of IKEA halogen lights, and then the biggest culprit was an old (15 years) network hub. I wasn't even using it at the time, just had left it powered up when I needed it for some quick testing months ago. Pulled the plug on that and the noise dropped immediately. The lights were more of bring down the noise floor a bit which was nice.

This is all because my antenna is almost right above my office on the roof.

Tomorrow I'll be going after the smaller yet still annoying RFI issues. I'm realizing that this is the never-ending quest of a ham to get rid of this stuff. I'm betting new RFI sources come and go all the time. Hopefully not too many from the neighbours. Smiley

Thanks again for the help!

Pete
VE6ETP
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WX7G
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Posts: 5987




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« Reply #5 on: November 26, 2013, 05:35:53 AM »

RFI can be like peeling an onion in that once you fix one RFI source another is revealed.
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