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Author Topic: Copper/Aluminum house wiring pigtails and RFI?  (Read 6431 times)
WB0GAZ
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Posts: 31




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« on: March 14, 2009, 01:18:55 PM »

I'm chasing a really severe RFI problem that's put me mostly QRT since (when first detected by me) December 2008. The signal is strong between 8 and 11 MHz, peaks at 9.4 MHz (S9+20 dB on a steppir vertical and TS-940S), is over S9 on 30M, and has energy on 40, 20 and 17M bands enough to impair receive here. It's on 7-by-24 since it started, doesn't vary in strength, and has a rain-static like character (not 60 Hz pulse rate like line power RFI.) It is slightly responsive to the 940's NB, but generally not enough to mitigate.

After much sleuthing (using an Arrow Antennas 6" DF loop, Miracle Ducker IL matcher, Yaesu VR500 hand-held tuned to 9.4 MHz in AM mode), I believe I have the problem isolated to a specific house (or at least down to a few houses) a short-block away, and I've met with the neighbor in the likely house twice in the last couple of weeks. He's lived there about a year, and sometime last year he said he had his aluminum house wiring "pigtailed" (copper ends put on at each outlet). This is a fairly common practice in the area as these houses were built in the 1960s with aluminum wiring. I didn't immediately see anything else a as a likely culprit inside or attached to the house.

My question is this - has anyone on the forum heard of RFI related to this sort of house wiring modification?

Thanks,

73 Dave WB0GAZ wb0gaz@hotmail.com
 
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AA4PB
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Posts: 12840




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« Reply #1 on: March 14, 2009, 05:30:10 PM »

It shouldn't be an issue. If the connections were not good you'd think he'd be having problems with the connections heating up.

With his cooperation it should be real easy to find out if the problem is coming from his house - just turn off his main breaker and see if you still have the noise.
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WB4BYQ
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Posts: 179




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« Reply #2 on: March 15, 2009, 01:19:09 PM »

I would make a small dipole type of ant, coax with maybe 1 foot legs for the dipole, and hook it to a radio and lay the ant on the meter box, and see which house is the loudest.  That is what i have done in my neighbor hood.  I have to work at trying to clean up the rfi. Then when the house is found, have the neighbor cut the power to the house, or turn devices off.  DVD, VCR, battery chargers, computer equipment
make this type of noise.
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WB4BYQ
Member

Posts: 179




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« Reply #3 on: March 15, 2009, 01:19:26 PM »

I would make a small dipole type of ant, coax with maybe 1 foot legs for the dipole, and hook it to a radio and lay the ant on the meter box, and see which house is the loudest.  That is what i have done in my neighbor hood.  I have to work at trying to clean up the rfi. Then when the house is found, have the neighbor cut the power to the house, or turn devices off.  DVD, VCR, battery chargers, computer equipment
make this type of noise.
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N5LRZ
Member

Posts: 0




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« Reply #4 on: March 19, 2009, 04:24:41 AM »

For the sake of argument lets just say that the house can be located and the problem is as you stated in your post--two different types of metal wires.


What can you do about it?

From the legal point you can file a complaint with the FCC.  The FCC might/perhaps have the time and send out a letter of notice stating you as a complainant siting FCC rules and regs telling them to fix it while siteing fines and such.  BUT OF COURSE you gotta know you just made a bitter enemey that will definately be seeking revenge.

IF a noise is in another persons house and they do not want to fix it you are probably going to be screwed becase the FCC just does not have the staff to enforce every little complaint it receives.

IF the noise is comming from a business from a store sign or because of an in the store dipslay etc etc then prepare to be definately screwed.  They are not going to care about your radio.

BUT look on the bright side....sooner or later that bad connection is going to heat up and the fixture is going to get so hot that the owner is going to have to fix the thing.

OHHH by the way, just curious, where I live the building codes used to/in the past allow alluminum wire in homes.  BUT DUE to house fires the codes have been changed to ban aluminum wires.  Just courious has your county and or state building codes banned aluminum wires and if so have they mandated that those with said aluminum rewire using copper?

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AA4PB
Member

Posts: 12840




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« Reply #5 on: March 19, 2009, 08:32:24 AM »

In general new homes can't be wired with aluminum (except for large circuits like the range). I've not heard of anyone mandating that all the aluminum wire in an older home be routinely replaced - that would be quite an expense. The typical upgrade is to add pigtails using a special grease on the aluminum-copper joint to prevent corrosion.

Again, there is no way that these joints should cause any RFI unless they are not good connections in which case the homeowner would likely be having other problems.
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KA7GKN
Member

Posts: 147




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« Reply #6 on: March 28, 2009, 09:06:05 PM »

This may have the potential for a dangerous situation.
And I don't mean just RFI!

I will explain:

Back in the 70's and perhaps even earlier many homes were wired with aluminum wire. We are all very aware of its dangers!

It is not really cost effective to "rewire" an entire home, so there are two options:

1. ensure all receptacles, built in light fixtures, and wall switches are specific for "aluminum wire".

2. Pig tail all wiring with #12thhn wire. Use Noalox or other anti-oxidant compound in the wire nut. Replace all outlets, switches, fixtures, GFI outlets!

 Mechanically twist the copper and aluminum together coat with Noalox and twist the correct sized wire nut secure. Do Not over tighten the wire nut! Do not nick or damage the aluminum wire in the process.

Once a year use an infrared thermometer to check for "hot spots". This can be a failing pigtail, or device, or worse.

NEVER use the press to insert type connection on switches and receptacles!! They do not ensure a solid and long term mechanical connection. Use the screw terminals and wrap the wire around it "correctly". If you do not know about this it's time to call an electrician! Avoid the 69 cent outlets!!! Buy Leviton
quality products! You'll thank me later.

When a copper and aluminum connection deteriorates and starts to fail, which they will, you will have arcing. This may not be obvious, and by this I mean you likely won't hear the arcing. You might hear something when turning on a light switch or plugging in a device.

That arcing may indeed be the RFI noise you are hearing.

If nothing is done to ensure the electrical system is safe remind the homeowner to check his fire insurance coverage.

Another item..inspect the circuit breaker panel box...circuit breakers such as Zinsco were made for aluminum wire. Those connections quite often loosen as the temperature changes. The panel needs to be stripped of all breakers and the buss bars coated with Noalox! This will require the power company to kill your power or a licensed electrician to enter the picture. A Ham Operator or homeowner are not trained to safely do this!

The aluminum wires need to have Noalox applied and reinserted into the circuit breaker, then properly torqued to ensure a correct mechanical connection.

Again no nicks on the aluminum wire what so ever!!!

Now you may ask how do I know all this? In a word "experience" My home was built in 1966 before building inspectors arrived here! The house is wired with all aluminum wire! When we purchased the house in 1988 we pigtailed everything and replaced every single switch, fixture, and outlet.

We had the power company out to inspect the electrical and they identified dangerously unsafe circuit breakers. They had arced internally and were no longer safe.

In December of 2008 I was bit by the dreaded aluminum wire again as the neutral wire in the power meter socket became loose and corroded and was slightly burnt! No fault of me or anyone just old aluminum wire failing. We lost our neutral line into the house...
Another story for another post.

We had to replace power meter socket. This required a building permit and all the hassles that go with it. The power company and a licensed electrician did most of the work. with my skill and knowledge I was able to help but in a very limited capacity. This was not an inexpensive repair but I do sleep better!

Take my word for it you don't want to lose your neutral! You can potentially damage a lot of your electrical stuff having an unbalanced system!

Good Luck and be safe!

Martin KA7GKN
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