[RFI] Powerline noise question

Hare, Ed, W1RFI w1rfi at arrl.org
Fri Dec 30 06:31:18 EST 2022 

Thanks for the feedback on the antenna.  I am going to add a link to the article to the ARRL.org RFI pages.

The distance of this source is surprising. First, this drives home the point that amateurs are always better off in dealing with the power company if the amateur can locate the source.  In practice, it is not at all likely that the power company would have found this.  Yes, it is their legal responsibility to find and correct any noise source on their equipment that causes harmful interference, but if they don't know how to track down something that far away, it simply is not going to happen.

ARRL has a number of cases where the amateur becomes angry that he has to track this down himself, and insists that the power company should just find it and fix it, or insists that the FCC should do so.  In an ideal world, this would be so, but the power companies DID come out, found some local noise, fixed it and then said they couldn't hear any more noise.  The result? The problem is not solved.  Yes, it's a pain in the butt to have to do their jobs for them, but if hams can find the noise, the likelihood that they will get it fixed goes up by at least 10 dB.

But at that distance, it is really important to correlate the noise with actual interference.  I was driving to Dayton one year and stopped by a complainant's location on the way back.  He had "tracked down" the noise to a location 3 miles away, on the other side of a river.  He sent me out with my mobile set up and, sure enough, there was noise there.  As I drove away from the source, the noise disappeared and, as I approached his QTH, I heard it weakly again.  Nope!  That was NOT his noise.  He had done what power companies often do -- driven around, found noise and made the assumption.

There are two ways to correlate noise to actual interference. The first is a "signature" method, optimized by Radar Engineers to be quite reliable. A time-domain (oscolloscope) pattern of the noise at the victim's antenna is taken and stored.  The troubleshooter then goes out into the world and find noise and gets its signature. If they do not compare, that is not the noise.  When a similar signature is found, that is almost always the noise.

A 2nd best, but valid, method is to ensure that the noise is heard all the way from the suspect source to the amateur's QTH.  There are often standing waves on the overhead lines that complicate this, but it can be valid.   To do this, one must be able to hear the noise on a mobile or portable receiver at the ham's QTH. This is not always possible. If you do, and you can definitely hear the noise all the way from the hams's QTH to the suspect source, that is a reasonable way of correlating noise, especially if it all that you have to go on.

From there, getting down to the exact pole can be a challenge. A step attenuator and a receiver with an S meter are musts.  Get to the area where the noise is strong.  Take the receiver and antenna and stand 3 feet away from the ground wire on an overhead transformer.  Attenuate to get about an S7 to S9 level on the S meter. Note it.  CAUTION!  Do not touch the ground wire!  Yes, it is supposed​ to be grounded, but there may be a defect on that pole somehow that has caused it to be ungrounded. Never touch ground wires, guy wires or anything else near a pole.

Now, go to the next pole with a ground wire and repeat the process. It will​ be louder at the actual pole. You may need to go a few poles in both directions to get confirmation.  Once you have found the pole, the utility should be able to locate the noise source on it.

The basic steps to resolving a power-line case are:


  1.  Read up and get smart about power-line noise. There is some excellent material on the ARRL Web page in the Technology area.
  2.  First, get a battery operated receiver, connect it to your antenna and kill the main power at your house.  If the noise doesn't go away, it's almost always not equipment at your house. (Watch out for UPS power supplies, though!)  If the noise goes away, it's something in your house. Turn on the breakers one at a time. If noise goes up, note which breaker, then turn it off again and move on to the next one.
  3.  If you are at all able, locate the pole.  You can do this yourself, or perhaps get some help through your local club, ARRL section Technical Coordinator, etc. Some areas have "RFI teams" that can and do locate RFI.
  4.  Contact your power company and report the noise as "radio interference."
  5.  We have to give the power company time to resolve it.  This can take as much as a couple of months, sadly, but that's just the reality in some areas.  They may go out, think they fixed it and never get back to you, so you may have to follow up.  Get a case number when you call it in.
  6.  Keep good records of everything.
  7.  If that doesn't resolve it, contact ARRL. Our staff may offer pointers, guidance and suggestions.  The best way to do this is via an "intake form" on our RFI page.  This will ask all the questions we'd have to ask verbally on the phone and let us cut right to the case when we have a conversation.
  8.  This is all being done in preparation for our initiating a process we have worked out with the FCC.  ARRL will ask you questions, mostly so we can determine:
   o The noise is harmful interference as defined by FCC rules. (This is another whole discussion!)
   o The correct source has been identified, i.e., it is power-line noise, not a local grow light or battery charger in the ham's own QTH.
   o Reasonable efforts have been made to resolve it.
  9.  If those steps have been met, ARRL will write a letter to the CEO of the electric utility, under the wing of our agreements with FCC staff, advising it of the complaint and the applicable rules.  The letter also offers ARRL help.  This often gets things moving, sometimes quickly.
  10. If that doesn't work, an escalating process could ultimately result in an FCC field investigation, but getting these done is hit or miss, as are the results.  Trust me, we all really want to never have to get to that step.

Ed Hare, W1RFI
ARRL Lab Manager



________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of Frank W3LPL <donovanf at starpower.net>
Sent: Thursday, December 29, 2022 10:53 PM
To: rfi <rfi at contesting.com>; PVRC <pvrc at mailman.qth.net>; topband <topband at contesting.com>
Subject: Re: [RFI] Powerline noise question

Hi Rick,

I recently built a WB8DSB man portable flag antenna (March 2021 QST)
for RFI geolocation, its performance far exceeds my expectations.
Its narrow deep null quickly, easily and definitively located the
source of very troublesome 160 meter RFI to a single power pole
more than three miles from my QTH.  Prior to constructing the
flag antenna I could locate the RFI to only within a few hundred
yards of the RFI source.

I built my flag antenna entirely out of materials I had on hand
from previous projects including 3/8 inch diameter fiberglass rods,
a pair of Advanced Receiver Research P1-30/20VD 20 dB HF preamps,
a case of eight AA batteries to provide power to the preamps,
a switchable attenuator and a Tecsun PL330 portable HF receiver.

I highly recommend this easily constructed RFI geolocation antenna
for the toolkit of any serious HF operator.

73
Frank
W3LPL





----- Original Message -----
From: "Richard" <richard at karlquist.com>
To: "rfi" <rfi at contesting.com>
Sent: Friday, December 30, 2022 3:15:32 AM
Subject: [RFI] Powerline noise question

I have a powerline noise coming from about 2 miles away, which is
nevertheless quite strong at my QTH.

Here are the symptoms:

1.  A 120 Hz noise burst at regular intervals, about 0.9 seconds apart.

2.  The noise goes away after a rain; then comes back after things dry
out.

3.  Can be heard from 500 kHz up to a few MHz.

4.  The noise is very strong along a road for a few miles.  There is a

power line that follows the road.  I haven't been able to localize it
better than

that so far.  From my QTH, though, it is definitely coming in at a
specific azimuth

which is consistent with the noisy road a few miles away.  (Using a loop
antenna

for DF'ing).

Any help appreciated.

--
Rick Karlquist
N6RK
_______________________________________________
RFI mailing list
RFI at contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI at contesting.com
http://lists.contesting.com/mailman/listinfo/rfi

More information about the RFI mailing list