Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Utility transformer causing RFI?  (Read 8626 times)
KC5MO
Member

Posts: 36




Ignore
« on: October 28, 2012, 10:01:41 AM »

Hey all,
 I have been having some intermittent S-7 to S-9+ arcing noise since it turned cool. It will start and last for a few minutes then stop and it is just like a street lamp failing, but it is 24/7.  I used a directional antenna to get a good bearing and then used a HT to zero in on the offender. What I found was strongest near a light pole except it was daylight and the light was off, but hidden in the bushes behind the light pole was the transformer for the underground utilities.
 I guess I am having a hard time thinking it is the transformer because I one would think it would be a constant arcing sound and not every 5 minutes so so ( 5 minutes quiet and around 3 to 5 minutes arcing ). Does anyone have any experience with this?

Thanks
Herb  KC5mO
Logged
WN2C
Member

Posts: 429




Ignore
« Reply #1 on: October 28, 2012, 10:54:35 AM »

If you are sure this is where the noise is coming from then call the power company and tell them what you found. Most power companies have a guy or 2 that goes out and verifies noise complaints. What else is around that may be causing this problem? Rea the power lines above ground or below?  Good luck getting it resolved.

73 de wn2c  Rick
Logged
KC5MO
Member

Posts: 36




Ignore
« Reply #2 on: October 28, 2012, 11:04:45 AM »

Hi Rick,
 Thanks for the reply,
 The lines are below ground.I will give them a call first thing tomorrow.

73
Herb  KC5MO
Logged
NK7Z
Member

Posts: 737


WWW

Ignore
« Reply #3 on: October 28, 2012, 11:05:25 AM »

Hi,
I have been fighting an RFI issue much like that over the past two years...  In some cases, the offending source is within a home, and the power lines are moving the RF around.  Underground wiring is interesting in that every transformer can radiate.  Here is a example...

1.  Something in a home is generating a lot of RFI.
2.  If you are VERY close, it will cover most of the HF spectrum, and a lot of the VHF spectrum.
3.  As you walk around listening, you are getting a combination of direct radiation, and re-re-radiated RFI from the power lines.
4.  When you approach a transformer, you start to pick up the re-radiated signal.
5.  When you walk away, you MAY start to pick up the direct signal, and the beam heading can change.

One of the best ways I have found to locate a source is to get a mobile rig, start driving around, when you are close, you will get blasted by the signal...  Drop out of your car, and start walking around with a directional antenna in the VHF range.  Use AM mode if possible for all testing.  Once you get really close the source, you will start to hear it in the VHF/UHF spectrum.  Sometimes an omni works better than a beam...  Just listen to the highest frequency that you hear the RFI at, and if it is sitting at S9, go higher in frequency, until it is at S5 or 6 or so...  Then walk around, in the direction the signal gets stronger.  As you approach the source, the signal will get stronger, and stronger, move up in frequency until you get around S 5 or 6 again...  Perform the above steps until you are on top of the source.

I have a review of a couple of RFI detecting devices on my web site at http://www.nk7z.net.  Select RFI Mitigation from the Navigation menu on the right to see them...

Good luck, RFI is tough to locate in some cases, and in others, it is simple...  This assumes that the source is wide-band, and sending out RFI in the VHF spectrum.

73's,
Dave
Logged

Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KB5UBI
Member

Posts: 97




Ignore
« Reply #4 on: October 28, 2012, 06:27:05 PM »

I've been have the same sort of problems here in Comal County. Comes and goes and from several sources. I have been working with the Tech from the Utility, but they are overwhelmed. I started by using my handheld (VX-7R) set in the 6 meter AM and driving around the neighborhood. I would then switch to 440 mhz AM using a hand held 10 element yagi to isolate it to the pole. The main problem was I found several noise sources within a 1/4 mile. The Utility fixed most of them but I'm still plagued by an S9 noise from 10 Mhz trough 6 meters that comes and goes. I finally put up a wire noise antenna and have been able to null out the noise by phasing; a temporary 200 dollar band-aid. Now that the weather is cooling, I guess it's time to attempt to find the final noise source.

Good luck, with diligence, you'll track it down. Make sure the interference is originating from the utility. Contact the Utility, keep records and give them 60 days to fix the problem. If they are no help, the ARRL has a Representative at 860-594-0214.
Logged
KC5MO
Member

Posts: 36




Ignore
« Reply #5 on: October 29, 2012, 02:46:27 AM »

Thanks for al the replies. Great web site Dave! I did find that using my dipole on my fence nulls the noise which is nice. I will keep you posted.

73
Herb  KC5MO
Logged
NK7Z
Member

Posts: 737


WWW

Ignore
« Reply #6 on: October 29, 2012, 06:38:18 AM »

Thanks for al the replies. Great web site Dave! I did find that using my dipole on my fence nulls the noise which is nice. I will keep you posted.

73
Herb  KC5MO

That probably means you are getting it as direct radiation if the null is sharp, if it is from a distributed source it becomes difficult to null, if from a point source easy...  Maybe you are really lucky, and the only source, (or rebroadcast point), is the transformer...  In my case, I get the noise from several miles of power lines...  So phase cancellation is out...
Logged

Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KB5UBI
Member

Posts: 97




Ignore
« Reply #7 on: October 29, 2012, 01:27:07 PM »

Originally, I had multiple noise sources, some were 24-7. When I identified the noise sources, the utility responded and fixed them, but they have not been able to find all of them themselves. Once I was down to a single noise source, it was easy to completely null the noise with phasing.

The utility has some good equipment, but not the knowledge or time to utilize the equipment. It's probably going to be up to you to find the source.  Do you have a use of a spectrum analyzer? I identified the location and emailed them a jpeg of the spectrum analyzer display which may have helped them to identify the problem device. The Tech told me they have a library of spectrum analyzer displays from different sources.

In the future, if the noise can not be eliminated by the utility, you can pick up a DX Engineering NCC-1 or MFJ-1026. The key is to have a good outdoor noise antenna. My noise antenna is a 25 foot vertical wire hung from a tree branch using a chain link fence as the ground plane and spaced more than 50 feet from my other antennas. The trick is to have the main signal's noise and the noise signal at the same amplitude, then adjust the phase to null the noise source. It works, but only for one noise source at a time because the null is very sharp.
Logged
K4PP
Member

Posts: 64




Ignore
« Reply #8 on: November 20, 2012, 05:38:24 PM »

Is it possible to have power line noise that is not across all bands? Like 15m and up?

 I am off work this week and wanted to enjoy some 15m but I have a noise that begins mid morning and subsides at night. It sounds like power line noise, raspy crackling. It begins after sun up with a few pops and cracks and works into a full on S5 noise. Today, when the noise was once at a constant S5 I fed the audio into my TEK 465B Oscilloscope and saw the noise cycle were occuring at 1/120th a burst a second, sometimes at 1/60th with the snappling crackling. The noise is not present at all from 20m down  but it is present on 15m and up at same level on both my tri band rotatable dipole and 40m monopole (listening on 15m).

Today I used my VX-8R on 2m AM with my Arrow antenna to locate what I believe is a pole or the line about 200-300 ft from my fixed antenna. However it's hard to tell, sometimes the noise seem to be from this way or that unless I am 100 ft from the pole either side and then the beam points to the pole. Can it be power line noise if it is only on 15m and up?

Thanks,

K4PP
Logged
KB5UBI
Member

Posts: 97




Ignore
« Reply #9 on: November 20, 2012, 11:03:02 PM »

It sounds exactly like one of the noise problems I have. You may want to try 440 AM.

I built a single quad loop for my VX-7R to go along with my yagi. The quad loop has sharp nulls off the sides and has helped me to quickly narrow down the source.

Seems like every time we fix one source, another one pops up. The more I use antenna phasing, the better I am getting at determining the distance of the noise source.
Logged
K4PP
Member

Posts: 64




Ignore
« Reply #10 on: November 21, 2012, 04:59:57 AM »

Thanks for the reply. Last night the noise remained present well into the night and early morning at S2-S3 but the signature changed to 60Hz with no 120, sometimes dropping off to a few snaps and pops. I got up early this morning and the last pop was heard at about 5:00am. Quiet as a mouse on 15m and up right now. I'll see what happens as the days wears on.

Thanks,

K4PP
Logged
KB5UBI
Member

Posts: 97




Ignore
« Reply #11 on: November 21, 2012, 05:11:41 PM »

You may have multiple sources like me. One at a time.
Logged
K4PP
Member

Posts: 64




Ignore
« Reply #12 on: November 22, 2012, 02:55:37 AM »

The noise did grow again yesterday and by afternoon S5 again. I drove around within a quarter mile of the neighborhood checking and everything was quiet, except when I go to that pole 300 ft over from the house and stand under it with the HT it is LOUD! I went ahead and called the utility company and a crew came by my house and I let him hear it and explained the problem, showed him some of my equipment. He just mentioned that they have a person who specializes in this and would have to call that in. We'll get through and enjoy the holiday and then hopefully I'll get a call from them to fix this.

Thanks for your help and Happy Thanksgiving


K4PP
Logged
KD1XH
Member

Posts: 16




Ignore
« Reply #13 on: November 26, 2012, 02:10:24 AM »

Anyone know what this could be?

http://www.youtube.com/watch?v=6FppsZjpMFM

It can be heard all through the spectrum up to about 35 MHz or so at my place, but the loudest peaks seem to be at around 3 MHz and 9-10 MHx. Strangely on AM broadcast I don't hear it, and am yet to find much of it in VHF AM. With my VX6 in AM mode on 35 MHz there were two nearby poles much louder than others. Not sure what good that info is.

Here's another clip from later that same night. At 1:00 AM local, the noise suddenly cleared up. It doesn't get this good at night anymore since...just S5-S6 buzz at most without the 20-over peaks after 1:00 AM. What happens at 1:00 AM, I have no idea . I have called the utility, hopefully they have someone who knows what they are doing.

http://www.youtube.com/watch?v=szEXe6NgiSg
Logged
W5WSS
Member

Posts: 1652




Ignore
« Reply #14 on: December 05, 2012, 04:49:54 PM »

K4pp is it possible that the noise is the sun moving overhead and a low horizontal antenna sensitive towards the zenith?
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!