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1-10 of 13 messages
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RFI on AC line
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by AD7VH on May 25, 2009
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I have been having a problem for quite a while now. I have been getting RF down the AC line of my house. I could not figure out where my RFI was coming from until recently.
It started out when I was trying to use a W2IHY dual band EQ. When I used a wallwart to power it, I would get a steady 100w carrier on SSB. I tried powering it off from my power supply and the problem ended. Later I tried to use a Nady 15 band EQ and an ART tube mic preamp and the problem was worse than with the W2IHY box. However, I can run the tube preamp into the W2IHY without any problems at all. As soon as I try to use the Nady EQ, forget it. If I try to power my laptop off from the adapter it locks up the mouse, but no problem on battery. My wife has the same problem with her laptop operated up stairs (my shack is in a basement).
I have a good ground. I have a piece of 3/4" copper pipe beat flat for a bus. I have this mounted to my wall using ceramic insulators. From there it goes outside, via an 8 gauge solid copper wire (only 5' long), to an 8 foot copper ground rod. If I remove the ground I notice that I get into my daughter's TV a little worse than normal, so it is doing something. As far as the AC line RFI, it doesn't make any difference.
I have tried all of the tricks to remove the RFI. I have put bypass caps on all of my audio leads. When I put beads on the power cable for the Nady EQ it actually made the RFI worse! I can switch to a dummy load and run 700w and don't get into any of my rack gear. When I go to any of my antennas I cannot run more than 20w without having problems. I don't have this problem with anything that is not connected to the AC.
Do any of the AC RFI filters actually work? I would like to try one, however, I do not want to spend money on something that may not work. Also, does anybody think that one of those coax isolators would help.
The antenna that I mainly use is an inverted L for 75m. It has a good grounding system as well. However, it is mounted to mast right next to the house. I know that this could be a proximity thing. The other thing is the way that the AC power is ran here: There is 1 transformer for every 5 houses! Has anybody seen anything like this before? Does anybody think that this could be causing the problem? The way that they are ran could give RF a good path. I thought that I was seeing things until I had my dad look at it. I have also had problems with low voltage for the 7 years that I have lived here.
I don't cause any RFI to anything else in the house except my daughter's TV and mine and my wife's laptops, and there is usually 3 TVs going all the time. My wife's cheap boombox even seems to be immune to RFI, and it is connected to the AC line. I have neighbors all around me and I have yet to get any complaints, which the way that these people are, if there was a problem I would have heard about it by now.
Any ideas how to correct this would be greatly appreciated.
John, AD7VH, east central Nevada
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RE: RFI on AC line
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by WB4BYQ on May 25, 2009
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There is several items that you could try. Amidon
FT-240-77 cores, wrapping the power cord around the core. The MFJ RFI power line filter, or I.C.E. Industrial Communication Engineers power line filter.
The MFJ is half the cost of the ice unit. Look at RFIchoke.com, this web site has good information on split ferrite cores. Look at the ARRL RFI handbook, also DX enginnering sells type 31 ferrite split cores.
good luck
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RE: RFI on AC line
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by AA4PB on May 25, 2009
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It sounds like a couple of issues involved. In the first case it appears that the power supply was a switching type that generated RFI picked up by your receiver. The other cases may indeed be RF being picked up and conducted by the power lines.
The best solution, if you can do it, would probably be to move the inverted-L feed away from the house. Make sure the inverted-L is fed against a good radial system. How are you feeding the inverted-L? Is the tuner or matching system located outside directly at the base? Unbalanced antennas like the inverted-L will feed RF back inside via the shield of the coax if you don't have a good radial system.
Grounding the rig itself almost never helps because its difficult to get a good RF ground inside. A good RF ground (radial system) at the base of the antenna will keep RF off the coax. Of course you have the additional issue of the vertical part of the inverted-L being close to the house and possible coupling RF directly into the AC wiring in the walls.
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RE: RFI on AC line
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by AD7VH on May 25, 2009
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As for the inverted L: I am using coax to feed it. I have three 50ft radials and twelve 20ft radials, with a ground rod at the feed. The matching system is 24” of 450 ohm twin lead connected to both conductors and then shorted at the other end. Moving the inverted L is not an option. I live on a 85’X100’ lot, which limits my options.
The one thing that I was going to try was to use a coax isolator first, and then if that doesn’t work (or only helps a little), get one of the AC line filters and try that.
This is definitely a complicated situation. I have dealt with RFI before, but not to this degree. When I was first licensed my closest HF antenna was 100’ away, so RFI was never an issue.
Living here, it has been a nightmare! I had less problems when I used to run legal limit out of the mobile!
I will get it rectified, it will just take some time and money. Anything can be fixed by throwing money at it. However, it won’t make the XYL very happy -- unless I throw some money at her!
Thanks for the help and anymore help will be appreciated as well.
73, John, AD7VH, east central Nevada
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RE: RFI on AC line
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by WX7G on May 26, 2009
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Your question needs to be re-written. What is interferring with what? Is a wall wart causing noise, is it the rig causing RF into the other equipment?
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RE: RFI on AC line
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by WB0MCO on June 1, 2009
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Have you tried a rf choke wound out of coax at the feed
point of the antenna? I use 28 feet of RG-8 wound on a
4 inch pvc pipe on every antenna down lead.
Everything in the shack is connected together with 1 1/2"
copper strap then ran to the out side single point
ground system using the same size copper strap.
My tower is right next to the house and most of my antennas are over the top of house, running 1KW with
no RFI problems.
Hope you find the problem,
Dave
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RE: RFI on AC line
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by AD7VH on June 5, 2009
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Dave, WX7G:
I thought that the question was to the point. I have RFI possible coming in through the AC line. That is, the signal that I am transmitting is coming back via the AC line -- not too hard to understand. I figured that this was clear while being concise.
John, AD7VH, east central Nevada
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RE: RFI on AC line
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by AA4PB on June 5, 2009
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You were fine until you started talking about the wall wart. I figured the wall wart was causing RFI to your receiver - a separate issue from the transmitter causing RFI to other devices.
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RE: RFI on AC line
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by N5LRZ on June 5, 2009
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You are making it all to complicated...
Step 1> see if the problem is comming from your house in the first place. Hook up your radio on a temp basis to a battery. Then turn off the main breaker to the house to shut off all electricity to the house. IF the noise does not go away then its not your house.
Step 2> IF the noise does go away after turning off all power to your house then turn on each of the power switches one by one leaving all the others off--turning on only ONE section at a time. When the noise comes back go to that particular part of the house and start to disconnect from the wall each appliance and fixture. Plug them in one by one listening for the return of the noise (remember it COULD be more than one appliance) until all appliances in that section have been checked. Continue this area and where required detailed search for all electrical sectors of your house. Be sure to also check ALL battery and cell phone chargers as well.
//reminder some sections may have more than one bad appliance and certain things are far more prone to generate RFI, plasma TVs for one and all kinds of battery chargers//
3> IF the noise is still present after you have eliminated your house and or targeted bad appliances in your house but the noise is still there, then time to have a buddy with a mobile drive around the neighborhood--it could be a neighbors house just as easily as your house.
4> IF you have cleared both your house and the immediate neighbors then its time to start looking for bad power poles and or the Electrical Company. Here is where that friend with an HF mobile comes in handy again. Remember that interference can be close or it can be quite far. Start in close and work outward.
IF the noise is comming from a neighbors house diplomacy may work or not. But if it does not you can always file a complaint with the FCC and yes the FCC has in the past sent letters of notice to neighbors.
IF the noise is comming from just bad power lines, then you may have to send a certified letter and file forms but know that utility companies resist expensive repairs at all costs and you may end up having to file and official complaint with the FCC. The good thing is that the FCC DOES threaten utility companies with fines. The bad part is that in order to reach that stage you may be listening to noise for quite a long while as you give the utility company reasonable time to fix the problem. SOME utility companies are better at fixing the problem than others.
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RE: RFI on AC line
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by AD7VH on June 5, 2009
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This is some useful information. The only problem is running the gear that requires 120V. I may just use one of my big batteries and an inverter to run my EQ and mic preamp. I know that there is most definitely problems with the power lines around here. We had problems a while back and they actually told me that there had not been anything done to them in well over 20 years. The phone lines are just about as bad, and I am surprised that I have not had an RFI issue with them yet.
This area is one of the most isolated areas of the lower 48. Upkeep is not done until something fails around here and people just don’t care. Heck, we even have analog phone lines, and the phone company does not even have a back up generator -- we lose power, we lose phones. I know that if the problem is from the power lines, I am going to have a fight on my hands.
I am fighting with the power company right now. They decided to replace the meter head without coming to my door. This resulted in my desktop computer crashing completely. They said that they did not think that anybody was home. Let me see, 3 cars are outside, so this should have been a clue!
As far as the wall wart is concerned. The problem with RFI coming down the AC line made it impossible to run my W2IHY EQ on the wall wart, but worked fine on my power supply. Obliviously, the wall wart is not filter very well.
This place is far worse than any place that I have ever lived when it comes to utility company's solving problems. Another example is how the cable TV here spews radiation all over the 2m band. I am just glad that I don’t operate much 2m. However, in the next few months I plan on setting up a station for 2m EME using WSJT, so I should work on this problem as well. Every time that I have a problem I have had to take it to the state or federal level to get it solved. The people around here think that by living here you have signed up to deal with everything that is encountered. I think that I will try to see if the problem is coming from the AC line and then report it to the FCC. Thanks for the advice and I will use it if necessary.
John, AD7VH, east central Nevada
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