Download
1 / 37
370 likes | 492 Vues
RFI – What is it and what can I do about it?. de K5GP Gene Preston. This power line started making a lot of noise. Rather than do this. Let’s go find the noise with this:. maximum signal off the end of the loop. maximum signal broadside to the loop. Small versus 1 Loop Pattern.
E N D
RFI – What is it and what can I do about it? de K5GP Gene Preston
maximum signal off the end of the loop maximum signal broadside to the loop Small versus 1 Loop Pattern
How to resonate the small loop ~19˝ each side
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?
440 MHz yagi on AM mode When we get close – switch to this.
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?
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
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.
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.
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.
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).
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 HL&P. 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, Ron, AB5WG
I suggested Ron build his own DF equipment. He constructed this loop:
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.
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 Reliant’s lawyers.
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 …
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. …
…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 didn’t fix the problem!
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
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
Low Tension Bell Insulators Are A Noise Source Spray with WD40
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.
