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Author Topic: BAD RFI....  (Read 9554 times)
AB9TX
Member

Posts: 22




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« on: December 28, 2012, 10:34:04 AM »

I'm looking for solutions for identifying this RFI on 80 meters. I have link below to look at it. I did all the basic steps including opening the house main breaker, using my portable rig in my car- tuned to one of these harmonics. It is quite loud around my next door neighbor's house.
It is 24/7 constant, no rotational or intermittant nature. It smells like a switching supply, and is loud. It is around 5khz wide and spaced 50khz.

Can someone suggest a simple directional antenna for 80 meters that I could build that would be managable? I would like to try and pinpoint this-
It may be coming from our outside utility distribution, which is underground. I have allready asked my neighbor if he might give me a hand, offering to repair or replace whatever it is. No luck there yet...

Anyhow- much appreciate any info, I guess this is the price of living in the city.

Earl
AB9TX





You-Tube:

http://youtu.be/0GZSX0h2o5s
« Last Edit: December 28, 2012, 11:26:35 AM by AB9TX » Logged
AA4PB
Member

Posts: 12980




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« Reply #1 on: December 28, 2012, 02:39:18 PM »

Usually, if you can hear it on 80M you can hear it on higher frequencies at a shorter range. When the power company "DFs" a noise issue they usually do it on VHF or higher where portable directional antennas are possible.

You could also try a portable broadcast band AM radio but it will not be as easy to pinpoint at that low frequency.
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WB4BYQ
Member

Posts: 179




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« Reply #2 on: December 28, 2012, 04:59:43 PM »

This may be a grow light for some type of plant that people grow in their homes. 

http://www.w0qe.com/RF_Interference/grow_light_electronic_ballasts.html

http://www.arrl.org/radio-frequency-interference-rfi

Mike Gruber at the ARRL can offer some suggestions of help, and the ARRL has established
a MOE  memorandum of understanding with the FCC, and Mike will write a letter much like the FCC to the neighbor about the RFI, the FCC will get a copy.  I used this approach twice. 

richard
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AB9TX
Member

Posts: 22




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« Reply #3 on: December 28, 2012, 05:06:52 PM »

Bob, thanks for the info. The RFI is from around 3 to 7.2 mhz as measured on my panadapter.

 And that is my main problem- building a directional micro mini 80 meter antenna. Something that is not 70 ft long. I was hoping someone who is knowlegable with "DFing" might have a simple design I could home brew.

The AM radio trick doesn't work in my case..

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WX7G
Member

Posts: 6197




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« Reply #4 on: December 28, 2012, 05:10:09 PM »

50 kHz spacing and one spectral line is at 3917.5 kHz...

50 kHz is too slow to be a switching power supply in a residence
The 50 kHz spacing tells us there is a crystal oscillator involved
The 5 kHz width tells us something is being modulated

Could it be a computer CRT monitor?

But you're looking to DF it. A short wire (3') and a short wave receiver that you carry around will help you find the house with the offending device. Then the fun really begins.
« Last Edit: December 28, 2012, 05:12:18 PM by WX7G » Logged
WB4BYQ
Member

Posts: 179




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« Reply #5 on: December 28, 2012, 05:14:49 PM »

Let us know what you find, and the resolution.

richard
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AB9TX
Member

Posts: 22




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« Reply #6 on: December 28, 2012, 05:33:09 PM »

Richard, that's it.... they are growing pot next door.

Except isn't there an off period? This junk is continuous.
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KZ1X
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Posts: 3229




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« Reply #7 on: December 28, 2012, 07:23:42 PM »


 And that is my main problem- building a directional micro mini 80 meter antenna. Something that is not 70 ft long. I was hoping someone who is knowledgeable with "DFing" might have a simple design I could home brew.



You could scale this down to the frequency range you need. 

http://www.k3zxl.com/Loop.htm


The web instructions for this antenna are EXCELLENT ... may be the best I've ever seen, anywhere.
Dan, if you are reading this, bravo and thanks for documenting your test antenna so well.

The ideal radio I have found for DF-ing is an Icom R-20.  If you have or can find one to borrow, terrific.  Other rigs will do, of course...

Take two 90 degree radial readings to your expected target and draw the lines on a scaled local map.  Then, go back and add a third line from some other angle ... and you're there.

gl

Steve KZ1X
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WX7G
Member

Posts: 6197




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« Reply #8 on: December 29, 2012, 06:34:44 AM »

If the noise source is in a house there isn't anything you can do to force them to shut it off. As the noise is not continuous from one end of the band to the other you could just avoid the frequencies it occupies.
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WB4BYQ
Member

Posts: 179




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« Reply #9 on: December 29, 2012, 09:13:06 AM »

know nothing about growing that stuff.  the rfi is flowing from their home to yours also by the power line from the transformer feed point,  also i have found that the rfi will flow on the ground system as well.  i guess the rfi is both common-mode and differential mode.  if you pursue the rfi issue just give yourself some time to work the problem.  maybe if you talk to the neighbor drop some information about what you think the problem is during the conservation, don't be accusing, but just think out loud while you talk.  i have been there in your shoes where i lived before now.

richard
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AB9TX
Member

Posts: 22




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« Reply #10 on: December 29, 2012, 09:28:25 AM »

National RF makes an RFDF Vector handheld unit. It is an active device.
Anyone use one of these?

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K1CJS
Member

Posts: 6055




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« Reply #11 on: December 29, 2012, 10:27:16 AM »

Could also be a plasma TV.  Some of the older ones were notorious for RF noise.
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WN2C
Member

Posts: 479




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« Reply #12 on: December 29, 2012, 05:02:05 PM »

Could be anything.  If you are sure it is coming from your neighbor's house, talk to him and tell him that he may have some electrical problem.  There was a story in QST or some where that a ham found in his neighbor's home a problem with his electrical in the attic and he kept the house from burning down.

Rick  wn2c
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WX7G
Member

Posts: 6197




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« Reply #13 on: December 29, 2012, 06:27:31 PM »

Bad RFI. Is there Good RFI?
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ZENKI
Member

Posts: 980




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« Reply #14 on: January 04, 2013, 10:39:15 PM »

Just make a small untuned or tuned loop if it is band specific. You can find details here

http://www.w0qe.com/RF_Interference/tracking_down_rf_interference.html

I used small EMC loops. I have both professional and homebrew versions that work well. I like the small sniffer loops because you can pinpoint  the exact spot of the RFI.
You really need to go around your own house first with a sniffer loop.

http://www.millertechinc.com/pdf_files/MTI%20TN101%20Simplest%20EMC%20Magnetic%20Field%20Probe.htm

I small 2 or 3 inch homebrew loop is the most useful size for nailing the interference source.

A SDR radio can be an invaluable tool as a RFI spectrum analyzer. I use one with my lap top and small loops. I can find most RFI within in 30 minutes.

Most noise comes from those nasty wall warts and other switch mode power supplies. Anything that has LED's in them like LED lights that are made in Chine will cause problems. All the Chinese manufacturers
have fraudulent  certification markings on their products. They being dumped all around the world and our governments are doing nothing about them. 99% of the EMC problems is from cheap Chinese junk
manufactured in China. The unfortunate thing is that big name companies like HP, Cisco, Nokia and even Apple are being fooled by these Chinese EMC fraudsters.  When you have companies that will poison their own babies, EMC
fraud  would not even register on the chinese manufacturers conscience!



I'm looking for solutions for identifying this RFI on 80 meters. I have link below to look at it. I did all the basic steps including opening the house main breaker, using my portable rig in my car- tuned to one of these harmonics. It is quite loud around my next door neighbor's house.
It is 24/7 constant, no rotational or intermittant nature. It smells like a switching supply, and is loud. It is around 5khz wide and spaced 50khz.

Can someone suggest a simple directional antenna for 80 meters that I could build that would be managable? I would like to try and pinpoint this-
It may be coming from our outside utility distribution, which is underground. I have allready asked my neighbor if he might give me a hand, offering to repair or replace whatever it is. No luck there yet...

Anyhow- much appreciate any info, I guess this is the price of living in the city.

Earl
AB9TX





You-Tube:

http://youtu.be/0GZSX0h2o5s
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