RFI

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RFI What is it and what can I do about it?

• de K5GP
• Gene Preston

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This power line started making a lot of noise.
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• Rather than do this.

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• Lets go find the noise with this

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Small versus 1 ? Loop Pattern
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How to resonate the small loop
19? each side
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What the 40 meter loop does

• Able to listen on the same noise frequency
• Able to get a rough idea of the direction
• Able to walk in that direction to get ever closer
  to the source
• Get close enough to the source to switch to a VHF
  or UHF frequency why?

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• When we get close switch to this.

440 MHz yagi on AM mode
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Why use a 440 MHz beam?

• Only hear the noise when very close
• Sharp forward beam clearly tells direction
• Beam is able to locate source on the pole
• Beam is able to identify the polarization
• All this information usually allows the likely
  defective component to be identified
• But are we absolutely sure this noise source is
  the correct noise source?

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Is this the right source?

• The ARRL recommends using special equipment that
  matches noise signatures
• An alternate approach is to use a time
  correlation
• I.e. when the HF band noise changes, such as
  going away, then check the UHF located source to
  see if it also has done the same thing
• I did this on/off correlation for a week

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Now its time to contact the power company.When
making contact, tell them you have identified a
noise source on pole xxxxx.Set a definite time
to meet with them at the site.
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Show them the noise on your receiver
loudly!Keep the receiver turned on while they
poke around looking for the source.When the
noise stops, the component is identified and can
be changed out.

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In my case, the component was a loose ground wire
the nut was loose. It was tightened and the
noise was gone when the circuit was
re-energized. The total time for the line crew
was only 30 minutes from the time they arrived.
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• Quick repair times usually foster a cooperative
  relationship with the power company.
• Finding the source may not be easy.
• Such is the case for a noise problem that
  occurred in the Reliant system (Houston).

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• Date Thu, 15 Nov 2001 Hi Gene I read your
  article in Technical Correspondence of QST this
  month and would like your suggestions.  The power
  company here in my area is Reliant Energy, former
  HLP.  They currently have a crew of two
  experienced personnel and one trainee on locating
  line noise and interference problems.   I have
  been fighting severe line noise problems for the
  past month in the HF spectrum.  I do have a very
  directional HF beam and a sensitive receiver with
  attenuator and scope (756 PRO).  From my QTH I
  can usually get them directed to a very specific
  area on the source of trouble.   In the past few
  weeks they have been replacing arrestors,
  switches, hardware, etc, but have yet to get to
  the source of the problem.  The problem is so
  severe that it makes accurate detection
  difficult, at least that is my assessment. I
  really have to crank in the attenuation to
  prevent receiver overload.  Either case, at the
  rate/method they are going it takes weeks or
  longer to troubleshoot and repair the problem. 
   In your 28 years in working the power industry
  have you discovered any process/method to speed
  up this detection and repair cycle?   Any
  suggestions you may have would be appreciated.  I
  am located in Sugar Land, near Houston. Thanks, Ro
  n, AB5WG  

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• I suggested Ron build his own DF equipment. He
  constructed this loop

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• Ron also got a 440 MHz yagi beam and tracked the
  noise to a transformer.
• I told him that transformers usually do not make
  radio noise.
• He was persistent in that the 440 MHz beam showed
  the transformer was the source of noise.

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• To test the transformer theory, the power to the
  transformer needed to be killed.
• But this transformer served a large business
  which would suffer economic losses if power was
  cut so Reliant did not do the test.
• Ron and others filed a complaint with the FCC.
  Reliant stopped their field work on the case.
  Open communication with Reliant employees were
  halted by Reliants lawyers.

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• First letter to Reliant from the FCC.
• May 23, 2002
• Mr. Steve Ledbetter, PresidentReliant Energy
  CompanyPO Box 1700Houston, TX 77251
• Dear Mr. Ledbetter
• The Federal Communications Commission has
  received complaints that equipment operated by
  your utility may be causing harmful radio
  interference to an operator in the Amateur Radio
  Service. The complainant is
• Edward J. Gerber, W5GCX2407 Briarlee
  DriveHouston, TX 77077
• The FCC has the responsibility to require that
  utility companies rectify such problems within a
  reasonable time

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• Second letter to Reliant from the FCC.
• August 9, 2002
• Michael C. Massengale, EsquireBaker Botts,
  LLPOne Shell Plaza910 LouisianaHouston, TX
  77002-4995
• Re Reliant Energy, Incorporated Radio
  FrequencyInterference to Amateur Radio Station
  W5GCX
• Dear Mr. Massengale
• This is in response to your letter of June 28,
  2002, on behalf of Reliant Energy, with respect
  to radio frequency interference from the
  operation of the company's electrical service
  equipment to Amateur Radio operators.
• The Enforcement Bureau appreciates your
  comprehensive response. However, your
  interpretation of applicable Commission rules
  with respect to this matter is in error in
  several material respects. Reliant Energy is
  obligated to eliminate the interference
  complained of.

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• Reliant must do all things necessary, and bear
  any and all necessary costs, to comply with its
  obligations as an operator of unlicensed devices
  pursuant to the Commission's Part 15 regulations.
  You are hereby requested to provide a written
  report within 30 days of receipt of this letter
  as to the steps that have been taken to eliminate
  this interference. Further enforcement action
  will be withheld pending receipt of that report.
  The Commission expects, however, a complete
  solution without further delay, and good faith on
  the part of your client.
• Reliant was about to face fines if they didnt
  fix the problem!

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• Reliant took out this transformer.

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• And replaced it with this one

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What have we learned?

• Finding the source of noise is the first step
• Well equipped hams can quickly locate the source
  of noise and should do so
• Its best to minimize the cost and time the power
  company spends on your problem
• As long as the power company is cooperative do
  not contact the FCC
• Send a formal complaint to the FCC after
  exhausting cooperative efforts

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Here are common sources of power line noise

• Loose bolts on wooden poles
• Strings of slack span insulators
• Leaky lightning arrestors
• High current connections that no longer have a
  low resistance contact
• High voltage lighting with arcing connections
• Cracked or leaky insulators

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Note the slack span and bell insulators
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Low Tension Bell Insulators Are A Noise Source
Spray with WD40
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Fiberglas/Rubber Insulators Are Low Noise
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Lightning arrestor and fuse cutout
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Air switch contacts can make radio noise
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Transformers, arrestors, and fuses
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A sign can radiate noise as a ¼ wave vertical
antenna
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Your noise may be coming from your own equipment
or within your house.Use the HF loop to check
out your neighboring houses. Offer to put in
ferrite filters to keep their noise contained.
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Here is a filter to remove telephone interference
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Questions?