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Author Topic: Any idea what might cause this power line noise?  (Read 5780 times)
W8ASA
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« on: November 27, 2013, 07:48:32 PM »

These pictures show the panadapter screen of a friend's IC-7600 with AGC off. The noise is horrific, and renders his QTH almost completely unusable for HF radio. The noise is awful even up to about 500 yards in any direction from his QTH.

So far, we have completely disconnected his house from the power grid and turned off all power, even the UPSs. Also, we drove around his neighborhood listening to my car's AM radio, and another ham's HT turned to 3 MHz.

Before we call the power company, we'd appreciate any ideas or experience.

Here's a link to photobucket. I hope it works: http://s1374.photobucket.com/user/w8asa/library/?sort=3&page=1

73,
Ken W8ASA
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KB4QAA
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« Reply #1 on: November 29, 2013, 07:43:48 PM »

When you see repetitive signals at even spacing you should thing switching powers supplies, whether stand alone or embedded in other devices like TV's, or computers, etc.  They may wander slightly in frequency.

When monitoring RFI, it is best to use AM mode.
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W8ASA
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« Reply #2 on: November 30, 2013, 02:33:36 PM »

Thanks for the reply. I was wondering about switching power supplies. The noise covers a HUGE area, so it might be coming from an industrial type unit. We will be delving into this more this coming week.

Good advice on using AM mode. I actually had known that, but left the xcvr in SSB mode for some unknown reason.

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K5LXP
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« Reply #3 on: December 02, 2013, 06:35:25 AM »

http://www.eham.net/ehamforum/smf/index.php/topic,93609.msg718161.html#msg718161

Mark K5LXP
Albuquerque, NM
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N3HEE
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« Reply #4 on: December 04, 2013, 04:21:10 AM »

Do you have a audio recording of the noise?  Does your friend have close neighbors?  Does the noise ever stop?  Is the noise weather dependent?  Rain, wind dependent? That does not look like power line noise since its so evenly spaced.  Looks more like a switching power supply or plasma tv noise.  Power line noise is very broad and more frequency independent.  It also has a 120 HZ component.  Using free computer software you can take a look at the noise on a audio spectrum analyzer.  I had this kind of noise last year and traced it to my next door neighbors cable tv equipment.  I replaced the switch mode wall warts with linear power supplies and that got rid of most of the noise.  It took months to track it down so be patient and document your steps as you go. 


I am currently working with my power company to find the source of power line noise.  They have been to my QTH and have connected their RFI locator (http://www.youtube.com/watch?v=xrG92ypjFvU) to my antenna and captured a signature of the noise.  They have driven around in my area and are trying to locate the source. 

Regards,

Joe
n3Hee
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W8ASA
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« Reply #5 on: December 06, 2013, 12:36:28 PM »

My friend who is having the problem was at a gathering, and found out that one of the people there actually works in the "right" department at the power company. He was due to go on travel so couldn't come out himself, but made sure that a friend in the company did come out. With all his equipment, he narrowed the problem within minutes to one particular pole a few houses away by a new development, but my friend didn't think to ask what the actual problem was.

The guy immediately put in a repair order, so now it's just a matter of time..... Sometimes, it's just knowing the right person.
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AA4PB
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« Reply #6 on: December 06, 2013, 12:58:04 PM »

It's something arcing - most likely an insulator or a loose connection. I've been able to track it down to a pole using an AM hand-held scanner. As you move up in frequency (VHF bands) the signal doesn't travel so far and it is easier to trace. Once you can give them the pole ID you can usually get the power company to fix it since it represents lost power to them.

The bad news is that very often the strong RFI from that pole is masking weaker RFI from other poles so when you fix that problem you will hear the next.

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KD8HMO
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« Reply #7 on: December 09, 2013, 01:13:09 PM »

Im lucky, my local co-op power company loves it when we call them about noise, especially when we track it down for them. It usually winds up being something on a pole that is wearing out or going bad. They get right on it usually. One time, I met a truck and showed them where I narrowed the source down and it was something wrong at a transformer.
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KJ4DAQ
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« Reply #8 on: December 11, 2013, 11:55:45 AM »

I had similar problem of RFI on entire AM and shortwave bands.  HF band was totally unusable.  It was very effective for the entire community.  Later found that RFI was generated from my house and particularly from a small wallwart power supply adapter (SMPS) supplied with my external harddrive enclosure purchase the previous day.  Disconnected the power adapter  and the RFI went silent.  Discontinued using the adapter and decided not to buy things through internet unless it is a reliable product
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