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Author Topic: Help Needed With RFI Source  (Read 5146 times)
N1UK
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Posts: 1401




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« on: October 29, 2013, 07:21:36 PM »

I was chatting with a ham in the UK yesterday and he was suffering with bad rfi. He said that the noise drops considerably when he cranks up his tower compared to when it iis sitting around roof level. This made me think that the noise source is very close to him. The noise comes and goes.

He recorded the noise and sent me a file. Can anyone identify what the noise source might be. I haven't heard anything like this before . I uploaded the file to mediafire.
I think either link here works....

http://www.mediafire.com/?bbxudwl60ggmb6i

http://www.mediafire.com/download/bbxudwl60ggmb6i/RFI_01.3gp



73 Mark N1UK
« Last Edit: October 29, 2013, 07:23:52 PM by N1UK » Logged
K5LXP
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Posts: 4465


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« Reply #1 on: October 29, 2013, 08:51:51 PM »

This made me think that the noise source is very close to him. The noise comes and goes.

Has he tried to isolated it by killing power to his QTH to see if it goes away?  Likely it's in his house.

Mark K5LXP
Albuquerque, NM
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N1UK
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« Reply #2 on: October 29, 2013, 08:58:40 PM »

That is what I think but the houses in the UK are very close, so it could be the house either side. 59+20 noise when his beam is at roof level and S7 when he cranks it up another 20 feet.

I will ask him tomorrow. Maybe he will post here.


Mark N1UK
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G1YIJ
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« Reply #3 on: October 30, 2013, 12:30:19 PM »

Cheers to Mark for starting the thread...
While checking the again for a possible source in my house, I checked out a
few bands. 14.286, 18.153, 21.224 & 28.493 all had the same noise (tone &
signal strength s9) at the same time. The noise moves up & down the bands at
a very slow pace. I have again today, removed every single plug in appliance
& switched off all fixed appliances in the property. Both lighting circuits
were also turned off, the noise was still there, no difference at all. As
Mark stated, in the UK most of us live very close together. My house is
joined on both sides to neighbours houses (on my qrz page detail map the
marker is on my house). It does seem to be neighbour related so for now I
will have to live with it, after all they do put up with my antennas.

Keith G1YIJ
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N3HEE
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Posts: 113




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« Reply #4 on: November 14, 2013, 06:50:26 AM »

That sounds like computer noise.  I had similar noise related to a computer.
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K5LXP
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« Reply #5 on: November 15, 2013, 06:02:23 AM »

I have again today, removed every single plug in appliance & switched off all fixed appliances in the property. Both lighting circuits were also turned off, the noise was still there, no difference at all.

You should try shutting off the mains to the structure.  That's the only way to know for sure you've eliminated all the possible sources in the home.  There's the chance you missed unplugging a hidden wall wart, or the noise source is from something that's hardwired to the circuit.

Mark K5LXP
Albuquerque, NM
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WI4P
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« Reply #6 on: November 23, 2013, 11:25:14 AM »

Hello Keith.  Could it be your power supply?
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WX7G
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« Reply #7 on: November 26, 2013, 05:41:14 AM »

The slow frequency drift tells us the source is probably a switching power supply. With most modern electronics having switching power supplies you have quite a selection of potential noise sources.
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