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Author Topic: Electronic Furnace Filter EMI - Heads up!  (Read 1266 times)
KO7I
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Posts: 134




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« on: November 09, 2016, 09:24:05 PM »

This Fall I had a local HVAC company out to service my furnace in preparation for winter. One of the first things the tech said is that I should switch to paper filters from the electronic filter.
I figured I'd give it a try.
I pulled the plug to the electronic filter and we called it good.
Later that evening I went up to my ham shack to check out the bands and I was shocked to see my normal S6 to S7 40M noise floor was now S2 - S3. I have been struggling with persistent QRN for years and I assumed it was from the large residential development surrounding my home. That darn electronic furnace filter was the cause of my interference. I went down to my garage and chopped the cord off flush with a case of the electronic filter.
Good Bye QRN!
73, Don KO7i
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SOFAR
Member

Posts: 824




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« Reply #1 on: November 10, 2016, 12:55:17 AM »

It's an electrostatic filter.

Another example that you should start by checking your home. I helped an older amateur that lives near me, by walking around with an AM radio tuned to a quiet spot between stations. Turned out to be arcing on a pole. He called, and they rectified it.

It's easier if you pinpoint the source, than try to have them DF it.
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KO7I
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Posts: 134




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« Reply #2 on: November 10, 2016, 04:11:12 AM »

Yes indeed.
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NK7Z
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Posts: 1534


WWW

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« Reply #3 on: November 11, 2016, 07:12:37 AM »

Check your home first, by doing a Power off test...  I helped a ham who had assumed he had RFI for the past 10 years, (yes, 10 years), from a power pole...  We did the power off test, and it ended...  Was a touch lamp...  Boy was he surprised...  His 80 meter RFI went from 20 over S9, to S5.  10 years lost due to an assumption...  Heavy price to pay.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
N8CBX
Member

Posts: 401




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« Reply #4 on: November 12, 2016, 05:43:22 AM »

Do a survey of home appliances too. I had +20db/S9 QRM every 15kc on all the HF bands, but strongest on 80M. I homebrewed a hand held 80M receiver (with directional finder antennas) and discovered it was our Maytag clothes washer.
Jan N8CBX
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Dayton Ohio - The Birthplace of Aviation
KO7I
Member

Posts: 134




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« Reply #5 on: November 12, 2016, 06:27:16 PM »

The most embarrassing part of this whole matter is that I am a professional EMC Engineer who got lazy and did not check my own house. My bad.
I do have a SDRPlay RSP and it makes a great spec an for troubleshooting RFI issues. I also fab'd a RF Sniffer Probe.
Venders give my lab samples of their filters and we do their marketing for them in exchange. When filters become obsolete, they purge the old stock which I retain for assisting local hams with EMC issues.
I did install one of those filters into a friends Maytag washing machine to solve an EMC problem he was having.
Like I said, I'm a pretty embarrassed about not catching the furnace filter interference issue until now.
73, Don KO7i

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KB2WIG
Member

Posts: 259




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« Reply #6 on: November 14, 2016, 10:15:37 AM »



D,

I think the answer to your furnace problem would be "cobler's children syndrome".

KLC
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